Class 8

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 17 The Beauty of Diversity Important Questions ensure conceptual clarity.

The Beauty of Diversity Extra Questions and Answers Class 8 Basic Science Chapter 17 Kerala Syllabus

The Beauty of Diversity Class 8 Important Questions

Question 1.
Regarding the levels of biodiversity, choose the correct statements.
i. Genetic diversity refers to the diversity at the ecosystem level.
ii. Species diversity refers to the variation within a species.
iii. Ecosystem diversity refers to the variety of different habitats in a region.
iv. Different varieties of mangoes in India represent genetic diversity.
(a) i, ii correct
(b) iii, iv correct
(c) i, iii correct
(d) ii, iv correct
Answer:
(b) iii, iv correct

Question 2.
Choose the correct statements about decomposers.
i. Green plants are examples of decomposers.
ii. Decomposers break down complex molecules in dead remains into simpler ones.
iii. Bacteria and Fungi are examples of decomposers.
iv. Decomposers are placed at the top of the food chain.
a) i, iv correct
b) ii, iii correct
c) i, iii correct
d) All are correct
Answer:
(b) ii, iii correct

Question 3.
Select the correct statements regarding ecological interactions.
i. In mutualism, both organisms benefit.
ii. In parasitism, both organisms are harmed.
iii. In commensalism, one benefits, and the other is neither harmed nor benefited.
iv. Predation is beneficial to both the predator and the prey.
a) i, iii correct
b) ii, iv correct
c) i, ii, iii correct
d) All are correct
Answer:
(a) i, iii correct

Question 4.
Complete the food chain by placing the organisms in the correct sequence: Snake, Eagle, Paddy, Rat.
a) _________ → (b) _________ → (c) _________ → (d) _________
Answer:
a) Paddy
b) Rat
c) Snake
d) Eagle

Question 5.
Fill in the blanks representing the trophic levels in the energy pyramid shown in Illustration 17.4.

Trophic level 4: (a) _________Consumers
Trophic level 3: Secondary Consumers
Trophic level 2: (b) _________Consumers
Trophic level 1: (c) _________
Answer:
(a) Tertiary
(b) Primary
(c) Producers

Question 6.
Complete the diagram illustrating the Carbon Cycle by filling in the processes (A), (B), and (C) based on Illustration 17.7.

Atmospheric CO₂ → (A) Plants → (B) Animals → (C) Atmospheric CO₂
Answer:
A) Photosynthesis
B) Consumption / Eating
C) Respiration

Question 7.
Define the following terms:
a) Habitat
b) Ecosystem
Answer:
a) Habitat: The natural surroundings where each living being lives.
b) Ecosystem: The community of plants, animals, and microorganisms in an area interacting with each other and with abiotic factors.

Question 8.
Give one example for each of the following ecological interactions:
a) Mutualism
b) Parasitism
Answer:
a) Mutualism: Flower and Butterfly (pollination for nectar) OR Lichens (Algae and Fungus).
b) Parasitism: Flea on a Dog OR Lice on humans.

Question 9.
What is the Red Data Book, and which organisation publishes it?
Answer:
The Red Data Book is a document containing information about rare and endangered animals and plants. It is published by the IUCN (International Union for Conservation of Nature).

Question 10.
Observe Figure 17.3 showing different habitats. List two abiotic (non-living) factors essential for the survival of organisms in the Desert habitat shown.

Answer:
Two abiotic factors essential in a desert are:
Sunlight (provides energy, but also contributes to high temperature).
Water (scarce, crucial for survival). (Other possible answers: Air, Soil type/ Sand).

Question 11.
Illustration 17.5 shows a Vanda plant growing on a tree.

a) Identify this type of ecological interaction.
b) Explain how each organism is affected.
Answer:
a) Commensalism.
b) The Vanda (orchid) benefits by getting support and access to sunlight without harming the tree. The Tree is neither benefited nor harmed.

Question 12.
Figure 17.7 shows deforestation. List two negative impacts of deforestation on biodiversity shown or implied in the comparison with Figure 17.6.


Answer:
Two negative impacts are:
Habitat Loss: The removal of trees destroys the homes and living spaces for many animals and plants seen in Fig 17.6.
Loss of Food Sources: Animals that depend on the trees or other forest plants for food lose their sustenance.
(Other possible answers: Soil erosion, disruption of food webs).

Question 13.
Explain why decomposers like bacteria and fungi are essential for the balance of an ecosystem.
Answer:
Decomposers break down dead organisms and waste products. This process is crucial because it returns essential nutrients (like carbon, nitrogen) back into the soil, water, and air, making them available for producers (plants) to use again. Without decomposers, nutrients would remain locked in dead matter, and the ecosystem would eventually run out of usable nutrients.

Question 14.
Why does the amount of energy available decrease at each higher trophic level in a food chain?
Answer:
Energy transfer between trophic levels is inefficient. When one organism consumes another, a large portion of the energy obtained is used by the consumer for its own life processes (like respiration, movement, maintaining body temperature) and is ultimately lost as heat to the environment. Only a small fraction of the energy is stored in the consumer’s body and becomes available to the next trophic level.

Question 15.
Explain the importance of biodiversity in pollination and seed dispersal.
Answer:
Pollination: Many plants rely on animals (like bees, butterflies, birds – part of biodiversity) to transfer pollen, which is necessary for fertilization and fruit/seed production. Without these pollinators, many plant species, including important food crops, could not reproduce.
Seed Dispersal: Animals (like birds, mammals – part of biodiversity) often eat fruits and disperse the seeds in their droppings far from the parent plant. This helps plants colonize new areas, increasing their chances of survival and maintaining genetic diversity across landscapes.

Question 16.
Evaluate the statement: “Protecting only the top predators like tigers is enough for biodiversity conservation.” Is this sufficient? Explain why or why not.
Answer:
No, protecting only top predators is not sufficient. While important, they are just one part of the complex ecosystem. Biodiversity conservation requires protecting all levels of the food web and their habitats. Producers (plants) form the base, herbivores control plant populations, and decomposers recycle nutrients. Protecting the entire ecosystem, including lower trophic levels and habitats, ensures the long-term survival of top predators and maintains overall ecological balance.

Question 17.
Explain the difference between In-situ and Ex-situ conservation methods, giving one example for each.
Answer:
In-situ conservation: Involves protecting species within their natural habitats. Example: National Parks (like Eravikulam) or Wildlife Sanctuaries (like Periyar).

Ex-situ conservation: Involves protecting species outside their natural habitats, often in controlled environments. Example: Zoological gardens (Zoos) or Botanical gardens.

Question 18.
Evaluate the importance of the People’s Biodiversity Register (PBR) in conservation efforts.
Answer:
The PBR is important because it is a local-level documentation of the biodiversity (microorganisms, plants, animals) present in a specific area, prepared with community participation. This detailed, localized information helps:
Understand the unique characteristics and availability of local species.
Identify species that may need conservation focus.
Involve the local community, making conservation efforts more effective and sustainable.
Provide baseline data for monitoring changes in biodiversity over time.

Question 19.
Classify the following as producers and consumers.
Lizard, Planktons, Paddy, Calotes, Carrot, Grasshopper, Tortoise, Algae, Snake
Answer:

Producers	Consumers
Paddy	Lizard
Carrot	Calotes
Planktons	Grasshopper
Algae	Tortoise
	Snake

Question 20.
Find out suitable example for the animal relations mentioned.
i. Parasitism ___________
ii. Mutualism ___________
iii. Commensalism ___________
Crops × Weeds
Mango tree × Vanda
Mango tree × Loranthus
Fish × Heron
Hermit crab × sea anemone
Answer:
i. Mango tree and Loranthus
ii. Hermit Crab – Sea anemone
iii. Mango tree and Vanda.

Question 21.
Which are the different types of conservation of biodiversity?
Answer:
These are mainly two types.

1. In-situ conservation in which organisms are conserved within their natural environment
2. Ex-situ conservation in which animals are protected out their natural environment.

Question 22.
Complete the illustration Suitably

Answer:
a. Environmental/Ecological services
b. Cultural services
c. Food, Medicine
d. Nutrient Cycle, Pollination

Question 23.
Classify the following into Exsitu and In-situ.
(Zoological Gardens, Sacred Groves, Gene banks, Biosphere Reserves, Botanical Gardens, National parks)
Answer:

In-situ	Ex-situ
National parks	Zoological Gardens
Sacred Groves	Gene Banks
Biosphere Reserves	Botanical Gardens.

Question 24.
Expand the following terms.
Answer:
JNTBGRI – Jawaharlal Nehru Tropical Botanic Garden and Research Institute.
MBG – Malabar Botanical Garden
RGCB – Rajiv Gandhi Centre for Biotechnology.

Question 25.
Why do all the food chains start from green plants?
Answer:
The basis of all food chain is the plants. They are the producers. These are eaten by the herbivores which in turn are eaten by the carnivores.

Question 26.
The members at the successive higher levels are lesser in number and larger in size in a food chain. What about their body weight? What would be the reason for that?
Answer:
In the successive higher levels in the food chain the number of consumers decreases and the size of their body increases. The number of producers will be very large. The number of animals which feed on them is less in number. But their body size increases.

Question 27.
Hay → Horse
Paddy → FowlFox
Phytoplankton → Tadpole → Fish → Man
Grass → Grasshopper → Frog → Snake → Vulture
Examine the food chain given above and classify them as primary consumers, secondary and tertiary consumers.
Answer:
Producers
Hay, Paddy, Phytoplankton, Grass

Primary consumer
Horse, Fowl, Tadpole, Grass hopper

Secondary consumers
Fox, Fish, Frog, Snake

Tertiary consumers
Vulture, Man

Question 28.
What will happen if the number of herbivores increase?
Answer:
If the number of herbivores increase they will eat away all the grass and shrubs and they will have to face shortage of food. The destruction of grass and shrubs will cause soil erosion and the top fertile soil will be washed away.

Question 29.
Animals which are facing extinction.
Answer:

• Wild goat
• Musk deer
• Indian wild Ass
• Lion tailed Monkey
• Lion
• Rhinoceros
• The large Indian Bustard
• Tiger
• Kashmir deer
• Himalayan Tiger
• Silver owl
• Panda

Question 30.
Write down the name of any two organisations that work for the protection of nature
Answer:
IUCN (International Union for
Conservation of Nature)
WWF (World Wide Fund For Nature)

Question 31.
Choose the appropriate ones from the box and complete the table

(a) Nilgiris	i) Wild life Sanctuary
(b) Periyar	ii) National Parks
(c) Silent Valley	iii) Biosphere Reserves
(d) Kadalundi	iv) Community Reserve
(e) Malabar Botanical Garden

Answer:
i. Wildlife Sanctuaries – b) Periyar
ii. National Parks – c) Silent Valley
iii. Biosphere reserves – a) Nilgiris
iv. Community reserves – d) Kadalundi

Question 32.
Ecological interactions and their examples are given in the boxes. Make pairs according to the model given below.
Model – Predation: Deer and tiger

Ecological interactions	Examples
Predation	Mango tree and loranthus
Mutualism	Deer and tiger
Parasitism	Flower and butterfly
Commensalism	Mango tree and vanda

Answer:
Predation – Deer and tiger
Mutualism – Flower and butterfly
Parasitism – Mango tree and loranthus
Commensalism – Mango tree and vanda

Question 33.
Observe the pictures
i) Identify and name the organisms given above.
ii) Mention their specific importance related to biodiversity conservation.


Answer:
(i) A. Lion – tailed macaque
(Scientic name: Macaca silenus)
B. i. Nilgiri tahr (Scientific name: Nilgiritragushylocrius)
ii) These organisms on the verge of extinction due to several reasons.

Question 34.
Analyse the given statement and answer the questions.
There exist diverse ecosystems in earth, each differs in richness of biodiversity.
i. Is it necessary to conserve all kinds of ecosystems? Why?
ii. Write any four services of biodiversity.
Answer:
a) Yes
Ecosystems are places where there is rich biodiversity. Destruction of an ecosystem means destruction of many living organisms. So, in order to protect living organisms, we have to protect natural ecosystems.

b) Availability of essential materials

• Food
• Medicine
• Fuels
• Construction materials
  Cultural Services
• Aesthetics
• Recreation
• Study Practice of rituals
• Ecological services
• Soil Formation
• Prevention of soil erosion.
  O₂, CO₂ balance
• Availability of freshwater
• Flood control
• Climate control
  Auxiliary services
• Nutrient cycling, Pollination, Biological Control. Seed dispersal

Question 35.
Give reason.
It is not possible to illustrate a food chain using the following organisms
Snake, Rat, Eagle
Answer:
Eagle feed on both rats and snakes. So we cannot illustrate food chain

Question 36.
Complete the table given below:

A	B	C
Rat	Primary consumer	(a)  ………………….
Paddy	(b) ………………….	first trophic level
snake	(c) …………………….	Third trophic level
Eagle	Tertiary consumer	(c)  ………………….

Answer:
a) Second trophic level
b) Producers
c) Secondary consumers
d) Fourth trophic level

Question 37.
Pickout the organisms that are related to commensalism from the following and write as a pair.
Mango tree, Loranthus, Vanda, Butterfly, Snail, Flower
Answer:
Mango tree – Vanda

Question 38.
Correct mistakes if any, in the underlined part of the following statements.
• Dodo is an extinct organism.
• Palode Tropical Botanical Garden is an example for In-Situ conservation.
• Indo-Burma Region is an Ecological hotspot.
Answer:
Palode Tropical Botanical Garden is an example for Ex-situ conservation

Question 39.
Analyse the given food chain and an-swer the following.
A: Paddy → Hen → Fox → Lion
B: Grass → Deer → Tiger
a) In these food chains A and Lion and Tiger belong to which trophic levels.
b) What is the role of these organisms in maintaining ecological balance?
c) Write two messages for the conservation of these organisms, for preparing a poster.
Answer:
a) Lion – Fourth trophical level
Tiger – Third trophical level

b)They control the number of organisms that they eat. If they become extinct, the number of organism in
the lower trophic levels will be increasing in number beyond a certain limit. It will cause imbalance to the environment.

c) Earth without wild life is life without beautiful things.
If you like to shoot animals, do it with a camera, not a gun.

Question 40.
Identify the examples of given ecological interactions and answer the questions.
(i) Mango tree and Loranthus
(ii) Mango tree and Vanda
a. Name the ecological interactions (i) and (ii)
b. Write the name and peculiarity of another ecological interaction.
Answer:
a. i) Parasitism
ii) Commensalism
b. Predators – Eg: Tiger and deer

The Beauty of Diversity Class 8 Questions and Answers Notes Basic Science Chapter 16 Kerala Syllabus

Question 41.
Which trophic level has the maximum amount of energy available?
a) Primary Consumers
b) Producers
c) Secondary Consumers
d) Decomposers
Answer:
(b) Producers

Question 42.
Which interaction is characterized by the relationship where one organism benefits and the other is harmed?
(a) Mutualism
(b) Commensalism
(c) Predation
(d) Parasitism
Answer:
(d) Parasitism (Note: Predation also involves harm, but parasitism is a longterm, dependent relationship, e.g., Flea and Cat).

Question 43.
The organization responsible for publishing the Red Data Book is:
(a) WWF
(b) BMC
(c) IUCN
(d) PBR
Answer:
(c) IUCN (International Union for Conservation of Nature)

Question 44.
A Purple Frog (Mahabali Frog) is often called a ‘living fossil’ primarily because:
(a) It is found only in the Himalayas.
(b) It comes out only once a year to mate.
(c) It has undergone very little evolutionary change over millions of years.
(d) It lives underground.
Answer:
(c) It has undergone very little evolutionary change over millions of years.

Question 45.
Define Biodiversity Hotspot
Answer:
Biodiversity Hotspot: A geographically rich area that harbors a large number of endemic species and is under threat from human activities.

Question 46.
Differentiate between In-situ and Ex-situ conservation.
Answer:
In-situ Conservation: Protecting organisms within their natural habitats (e.g., National Park). Ex-situ Conservation: Protecting organisms outside their natural habitats in controlled conditions (e.g., Zoological Garden).

Question 47.
What is the main role of the Fungus component in the symbiotic relationship of a Lichen?
Answer:
The Fungus provides structure, protection, and helps in the absorption of water for the lichen organism.

Question 48.
Why is the amount of available energy found to decrease at successive trophic levels?
Answer:
Energy is lost as heat at each transfer step between trophic levels as organisms use energy for respiration and metabolic processes.

Question 49.
Explain the concept of Ecosystem Diversity with an example.
Answer:
Ecosystem Diversity: This refers to the variety of different habitats, ecosystems, and ecological processes found in an area.
Example: The diversity of hills, rivers, mangrove forests, and paddy fields found within a single region.

Question 50.
Differentiate between Genetic Diversity and Species Diversity. (2 points each)
Answer:
Genetic Diversity:
Variations within the individuals of a single species.
Example: Different varieties of rice or mango. Species Diversity:
Species Diversity.
The variety and number of different species in a particular area.
Example: The difference between a forest containing elephants, tigers, and bamboo plants.

Students often refer to Kerala State Syllabus SCERT Class 8 Maths Solutions and Class 8 Maths Chapter 10 Decimal Forms Questions and Answers Notes Pdf to clear their doubts.

SCERT Class 8 Maths Chapter 10 Solutions Decimal Forms

Class 8 Kerala Syllabus Maths Solutions Chapter 10 Decimal Forms Questions and Answers

Decimal Forms Class 8 Questions and Answers Kerala Syllabus

Earlier Forms (Page 164)

Question 1.
Write in fractional form, the numbers given in decimal form below:
(i) 0.1
(ii) 0.01
(iii) 0.11
(iv) 0.101
(v) 0.0101
Answer:
(i) 0.1 = \(\frac {1}{10}\)
(ii) 0.01 = \(\frac {1}{100}\)
(iii) 0.11 = \(\frac {11}{100}\)
(iv) 0.101 = \(\frac {101}{1000}\)
(v) 0.0101 = \(\frac {101}{10000}\)

Some Other Fractions (Page 166)

Question 1.
Write the fractions below in decimal form:
(i) \(\frac {3}{20}\)
(ii) \(\frac {3}{40}\)
(iii) \(\frac {13}{40}\)
(iv) \(\frac {7}{80}\)
(v) \(\frac {5}{16}\)
Answer:
(i) \(\frac{3}{20}=\frac{3 \times 5}{20 \times 5}=\frac{15}{100}\) = 0.15

(ii) 40 = 2 × 2 × (2 × 5)
Multiplied by 5 × 5
(2 × 5) × (2 × 5) × (2 × 5) = 1000
It is a multiple of 10.
\(\frac{3}{40}=\frac{3 \times 5 \times 5}{40 \times 5 \times 5}=\frac{75}{1000}\) = 0.075

(iii) 40 = 2 × 2 × (2 × 5)
Multiplied by 5 × 5
(2 × 5) × (2 × 5) × (2 × 5) = 1000
It is a multiple of 10.
\(\frac{13}{40}=\frac{13 \times 5 \times 5}{40 \times 5 \times 5}=\frac{325}{1000}\) = 0.325

(iv) 80 = 2 × 2 × 2 × (2 × 5)
Multiplied by 5 × 5 × 5
(2 × 5) × (2 × 5) × (2 × 5) × (2 × 5) = 10000
It is a multiple of 10.
\(\frac{7}{80}=\frac{7 \times 5 \times 5 \times 5}{80 \times 5 \times 5 \times 5}=\frac{875}{10000}\) = 0.0875

(v) 16 = 2 × 2 × 2 × 2
Multiplied by 5 × 5 × 5 × 5
(2 × 5) × (2 × 5) × (2 × 5) × (2 × 5) = 10000
It is a multiple of 10.
\(\frac{5}{16}=\frac{5 \times 5 \times 5 \times 5 \times 5}{16 \times 5 \times 5 \times 5 \times 5}=\frac{3125}{10000}\) = 0.3125

Question 2.
Find the decimal form of the sums below:
(i) \(\frac{1}{5}+\frac{1}{25}+\frac{1}{125}\)
(ii) \(\frac{1}{5}+\frac{1}{5^2}+\frac{1}{5^3}+\frac{1}{5^4}\)
(iii) \(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}\)
Answer:

Question 3.
A two-digit number divided by another two-digit number gives 5.875. What are the numbers?
Answer:
5.875 = \(\frac {5875}{1000}\)
5875 = 5 × 5 × 5 × 47
1000 = 5 × 5 × 5 × 8

5.875 = \(\frac{5875}{1000}=\frac{5 \times 5 \times 5 \times 47}{5 \times 5 \times 5 \times 8}=\frac{47}{8}\)
But 8 is not a two-digit number.
So we multiplied both numerator and denominator by 2, and we get
\(\frac{47}{8}=\frac{94}{16}\)
5.875 = \(\frac {94}{16}\)

New forms (Page 172)

Question 1.
Find fractions with powers of 10 as denominators that get closer and closer to each of the fractions below, and write the decimal form of each:
(i) \(\frac {5}{6}\)
(ii) \(\frac {1}{9}\)
(iii) \(\frac {1}{11}\)
Answer:

Question 2.
Prove that the numbers \(\frac{1}{10}, \frac{11}{100}, \frac{111}{1000}, \ldots\) get closer and closer to \(\frac {1}{9}\).
(ii) Find the decimal forms of \(\frac{1}{9}, \frac{2}{9}, \frac{3}{9}, \frac{4}{9}, \frac{5}{9}, \frac{6}{9}, \frac{7}{9}, \frac{8}{9}\)
(iii) What are the decimal forms of \(\frac {2}{3}\)?
Answer:

Question 3.
Compute the following and write answers in decimal form:
(i) 0.111… + 0.222…
(ii) 0.333… + 0.777…
(iii) 0.333… × 0.666…
Answer:
(i) 0.111 = \(\frac {1}{9}\)

Question 4.
For each of the fractions below, write the decimal form of a fraction with a difference less than \(\frac {1}{1000}\)
(i) \(\frac {1}{3}\)
(ii) \(\frac {1}{6}\)
(iii) \(\frac {2}{3}\)
(iv) \(\frac {5}{6}\)
(v) \(\frac {1}{7}\)
Answer:
(i) \(\frac {1}{3}\) = 0.333
(ii) \(\frac {1}{6}\) = 0.166 (or 0.167)
(iii) \(\frac {2}{3}\) = 0.666 (or 0.667)
(iv) \(\frac {5}{6}\) = 0.833
(v) \(\frac {1}{7}\) = 0.142

Class 8 Maths Chapter 10 Kerala Syllabus Decimal Forms Questions and Answers

Class 8 Maths Decimal Forms Questions and Answers

Question 1.
What is the decimal form of the fraction \(\frac {1}{8}\)?
(A) 0.18
(B) 0.125
(C) 0.8
(D) 0.0125
Answer:
(B) 0.125

Question 2.
Which of the following fractions has the decimal form 0.04?
(A) \(\frac {1}{4}\)
(B) \(\frac {4}{10}\)
(C) \(\frac {1}{25}\)
(D) \(\frac {2}{5}\)
Answer:
(C) \(\frac {1}{25}\)

Question 3.
Read the given statements.
Statement I: The fraction \(\frac {1}{3}\) cannot be written as a fraction with a denominator that is a power of 10 (like 10, 100, 1000).
Statement II: The decimal form of \(\frac {1}{3}\) is the recurring decimal 0.333….
Choose the correct answer:
(A) Statement I is true, and Statement II is false.
(B) Statement I is false, and Statement II is true.
(C) Both statements are true.
(D) Both statements are false.
Answer:
(C) Both statements are true

Question 4.
Read the given statements.
Statement I: 0.03 = \(\frac {3}{100}\)
Statement II: 0.03 can be split as \(\frac {0}{10}\) + \(\frac {3}{100}\).
Choose the correct answer:
(A) Statement I is true, and Statement II is false.
(B) Statement I is false, and Statement II is true.
(C) Both statements are true, and II explains I.
(D) Both statements are false.
Answer:
(C) Both statements are true, and II explains I.

Question 5.
If \(\frac {1}{9}\) = 0.111…, then what is the decimal form of \(\frac {5}{9}\)?
(A) 0.5
(B) 0.0505…
(C) 0.555…
(D) 0.9595…
Answer:
(C) 0.555…

Question 6.
What is the missing number in the expansion of 0.72?
0.72 = \(\frac{7}{10}+\frac{\cdots .}{100}\)
(A) 7
(B) 2
(C) 72
(D) 0
Answer:
(B) 2

Question 7.
Write in decimals
(a) \(\frac {1}{9}\)
(b) \(\frac {2}{9}\)
(c) \(\frac {1}{7}\)
(d) \(\frac {1}{11}\)
(e) \(\frac {2}{11}\)
(f) \(\frac {1}{12}\)
Answer:
(a) 0.111…
(b) 0.222…
(c) 0.14285…
(d) 0.090909…
(e) 0.181818…
(f) 0.08333…

Question 8.
Find the fraction of the denominator that is a power of 10 equal to each of the fractions below, and then write their decimal forms:
(i) \(\frac {1}{50}\)
(ii) \(\frac {3}{40}\)
(iii) \(\frac {5}{16}\)
(iv) \(\frac {12}{625}\)
Answer:

Question 9.
Find the fraction of the denominator that is a power of 10, getting closer and closer to each of the fractions below, and then write their decimal forms.
(i) \(\frac {5}{6}\)
(ii) \(\frac {3}{11}\)
(iii) \(\frac {23}{11}\)
(iv) \(\frac {1}{13}\)
Answer:

Question 10.
(i) Explain using algebra that the fractions \(\frac{1}{10}, \frac{11}{100}, \frac{111}{1000}, \ldots\) get closer and closer to \(\frac {1}{9}\).
(ii) Using the general principle above on single digit numbers, find the decimal forms of \(\frac{2}{9}, \frac{4}{9}, \frac{5}{9}, \frac{7}{9}, \frac{8}{9}\) (Why \(\frac {3}{9}\) and \(\frac {6}{9}\) left out in this?)
(iii) What can we say in general about those decimal forms in which a single digit repeats?
Answer:
(i) Let x be the number
\(\frac{x}{9}-\frac{x}{10}=\frac{x}{90}=\frac{x}{9}-\frac{11 x}{100}=\frac{x}{900}\)



(\(\frac {3}{9}\), \(\frac {6}{9}\). These fractions having common factor in the numerator and the denominator.
(iii) Repeated decimals.

Question 11.
(a) Find the decimal form of \(\frac {1}{4}\).
(b) Write the decimal form of \(\frac{7}{10}+\frac{3}{100}+\frac{4}{1000}\).
Answer:

Question 12.
(a) Write the decimal forms of \(\frac {1}{3}\) and \(\frac {1}{9}\).
(b) What is the decimal form of (0.33333….)²?
Answer:

Question 13.
Write the decimal forms of \(\frac {3}{25}\) and \(\frac {1}{8}\).
Answer:
\(\frac{3}{25}=\frac{3 \times 4}{25 \times 4}=\frac{12}{100}\) = 0.12
\(\frac{1}{8}=\frac{1 \times 125}{8 \times 125}=\frac{125}{1000}\) = 0.125

Question 14.
(a) Write the decimal form of the fractions \(\frac {1}{2}\) and \(\frac {2}{5}\).
(b) If \(\frac {4}{k}\) is a fraction between \(\frac {1}{2}\) and \(\frac {2}{5}\). What is k?
(c) Write the decimal form of the fraction \(\frac {4}{k}\).
Answer:

If \(\frac {4}{k}\) is between \(\frac {1}{2}\) and \(\frac {2}{5}\), then \(\frac {4}{k}\) is between \(\frac {4}{8}\) and \(\frac {4}{10}\).
Then the number is \(\frac {4}{9}\)
∴ k = 9
(c) \(\frac {4}{9}\) = 0.444…

Question 15.
(i) Find the decimal form of \(\frac {1}{11}\).
(ii) Find the decimal forms of \(\frac {2}{11}\), \(\frac {3}{11}\).
(iii) What is the decimal form of \(\frac {10}{11}\)?
Answer:

Question 16.
Write the results of the operations below as decimals:
(i) (0.333….)²
(ii) \(\sqrt{0.444 \ldots \ldots}\)
Answer:

Question 17.
Write the decimal form of \(\frac {1}{6}\)
Answer:
\(\frac {1}{6}\) = 0.1666…..

Class 8 Maths Chapter 10 Notes Kerala Syllabus Decimal Forms

Fractions with Powers of 10 as Denominators
Fractions with powers of 10 as denominators can be written in decimal form.
\(\frac {3}{10}\) = 0.3
\(\frac {54}{10}\) = 5.4
\(\frac {29}{100}\) = 0.29
\(\frac {54}{100}\) = 0.54
\(\frac {347}{1000}\) = 0.347
\(\frac {54}{1000}\) = 0.054

Any number in decimal form can be written using fractions with powers of 10 as denominators.
0.7 = \(\frac {7}{10}\)
0.91 = \(\frac {91}{100}\)
0.673 = \(\frac {673}{1000}\)

Decimal numbers can be splitted according to place value.

Some Other Fractions
Convention of some fractions, whose denominators are not powers of 10.

New forms
Conversion of some fractions, whose denominators were not powers of 10.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 17 The Beauty of Diversity Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 17 The Beauty of Diversity Question Answer Notes

Class 8 Basic Science Chapter 17 Notes Kerala Syllabus The Beauty of Diversity Question Answer

The Beauty of Diversity Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Based on Box A, identify and write the appropriate items from Boxes B and C.

A	B	C
1. Parasitism	a. At first, harm to both; later, benefit for the winner.	a. Butterfly and the flower.
2. Predation	b. Beneficial to one, neither beneficial nor harmful to another.	b. Vanda and mango tree.
3. Commensalism	c. Beneficial to both organisms.	c. Tiger and deer.
4. Mutualism	d. Beneficial to one, harmful to another. The prey becomes food for the predator.	d. Weed and crop.
5. Competition	e. One benefits, the other is harmed.	e. Cat and flea.

Answer:

A (Interaction)	B (Description)	C (Example)
1. Parasitism	e. One benefits, the other is harmed.	Cat and flea.
2. Predation	d. Beneficial to one, harmful to another. The prey becomes food for the predator.	Tiger and deer.
3. Commensalism	b. Beneficial to one, neither beneficial nor harmful to another.	Vanda and mango tree.
4. Mutualism	c. Beneficial to both organisms.	Butterfly and the flower.
5. Competition	a. At first, harm to both; later, benefit for the winner.	Weed and crop.

Question 2.
Examine the illustration and answer the following questions.

a) Rearrange the given food chain in the correct order.
b) Identify and write the producer, primary consumer, secondary consumer and tertiary consumer in the food chain.
c) Which organism belongs to the third trophic level in this food chain?
d) If the fish in this food chain completely disappear, how would it affect the ecosystem?
Answer:
a) Algae → Tadpole → Fish → Kingfisher
(Reasoning: Algae are producers (plants). Tadpoles eat algae. Fish eat tadpoles. Kingfishers eat fish.)

b)

• Producer: Algae (Makes its own food).
• Primary Consumer: Tadpole (Eats the producer).
• Secondary Consumer: Fish (Eats the primary consumer).
• Tertiary Consumer: Kingfisher (Eats the secondary consumer).

c) Fish
(Reasoning: Trophic Level 1 = Producer (Algae); Trophic Level 2 = Primary Consumer (Tadpole); Trophic Level 3 = Secondary Consumer (Fish)).

d)

• The Kingfisher population might decrease or move elsewhere due to a lack of food (fish).
• The Tadpole population might increase significantly because their main predator (fish) is gone.
• An increase in tadpoles could lead to a decrease in the Algae population due to overgrazing.
• This disrupts the balance of the ecosystem.

Question 3.
A food chain created by a student is given below. Examine it and answer the following questions.

a) Is the food chain created by the student correct? What is your opinion? What is the justification for it?
b) What would happen if decomposers like bacteria did not exist?
c) Write an example of a decomposer other than bacteria.
Answer:
a) No, the food chain is incorrect.
Justification: A food chain shows the flow of energy from producers to consumers. Bacteria are decomposers, not consumers. Decomposers break down dead organic matter from all trophic levels (including dead paddy plants), but they are not typically shown as the next step after a producer in a simple feeding chain. A correct chain would be Paddy Plant Herbivore (e.g., Rat).

b) If decomposers did not exist, dead plants and animals would not break down effectively. Nutrients locked within this dead organic matter would not be returned to the soil, water, and air. Over time, producers (plants) would run out of essential nutrients, and the entire ecosystem would eventually collapse. Dead bodies would accumulate everywhere.

c) Fungi (e.g., mushroo1ms, mould).

Basic Science Class 8 Chapter 17 Question Answer Kerala Syllabus

Texbook Page No : 269

Question 1.
Which are the living organisms that you see in the picture (Biodiversity Park)?
Answer:
Based on a typical biodiversity park setting, one would see trees, flowering plants, students (humans), birds, butterflies, and potentially insects on the ground.

Question 2.
In what different ways can you classify the organisms you identified?
Answer:

• Plants vs. Animals: Trees and bushes vs. Birds and Humans.
• Vertebrates vs. Invertebrates: Birds / Humans vs. Insects.
• Terrestrial vs. Aquatic: If there is a pond, organisms can be classified by where they live.:

Question 3.
Apart from the organisms you identified in the picture, what other organisms can be seen in a biodiversity park?
Answer:
Soil organisms (earthworms, millipedes), microorganisms (bacteria, fungi), reptiles (lizards, garden snakes), and various insects (ants, beetles).

Question 4.
Why is this place called a biodiversity park?
Answer:
Because it is a protected area designed to conserve a wide variety of plant and animal species (biodiversity) in one location, allowing them to thrive in their natural habitat.

Textbook Page No : 270 & 271

Question 5.
What conclusions can we arrive about the biodiversity?
Answer:
Biodiversity is vast and not yet fully discovered. Even today, hundreds of new species are being found, indicating that our forests and ecosystems hold many secrets and hidden species.

Question 6.
What are the organisms found only in these habitats?
Answer:
Organisms have specific adaptations that limit them to particular environments.

• Coral Reef: Corals, sea anemones, clownfish, starfishes.
• Mangrove Forest: Mangrove trees (plants with breathing roots), mud-skippers (fish that can move on mud), crabs, water birds.
• Desert: Cactus plants (modified leaves to save water), camels, rattle snakes, scorpions.
• Wetlands: Water lilies, lotus, frogs, cranes, dragonflies.

Question 7.
What are the non-living (abiotic) factors that help the survival of organisms in these habitats?
Answer:
Abiotic factors are the non-living parts of the environment that influence living organisms.

• Coral Reef: Saline (salty) water, sunlight penetration, steady water temperature. dissolved oxygen.
• Mangrove Forest: Brackish water (mix of salt and fresh water), clay-rich/muddy soil, tides,
• Desert: High temperature, intense sunlight, scarcity of water, sandy soil.
• Wetlands: Abundance of fresh water, marshy soil, moderate temperature.

Let’s Find

Question 8.
“Some organisms are able to live only in certain habitats. Why?”
Answer:
Organisms have specific adaptations (physical features or behaviors) evolved over huge periods of time that allow them to survive only in specific conditions (e.g., gills for breathing in water, thick fur for warmth in polar regions).

Question 9.
Have you noticed that a single organism can exist in different forms as shown in the pictures?
Answer:
Yes. Some organisms undergo a process called metamorphosis, where they change their form completely during their life cycle.
butterfly (Egg → Larva/Caterpillar → Pupa → Adult) or a frog (Egg → Tadpole → Frog).
Example: A frog starts as an egg, hatches into a tadpole (which lives in water and has a tail), and eventually grows legs and loses its tail to become an adult frog. This allows the organism to live in different ecosystems (water vs. land) at different stages of its life.

Textbook Page No : 273 & 274

Question 10.
Identify and write down which level of biodiversity that each of the following represents. (Based on Illustration 17.1: Ecosystem diversity, Species diversity, Genetic diversity).


Answer:

Question 11.
What does the poster (Illustration 17.2) indicate?

Answer:
It highlights the “International Day for Biodiversity” (May 22) and the theme “Our biodiversity, our food, our health,” emphasizing that our survival depends on nature.

Question 12.
How does biodiversity benefit each living organism?
Answer:
It provides food, shelter, oxygen, and maintains the ecological balance necessary for survival.

Question 13.
Shall we collect information on these topics and organize a seminar in the class on the topic “Biodiversity and the Survival of Living Beings”.
Seminar subtopics
• Food, clothing, shelter, fuel, medicines and biodiversity.
• Biodiversity and the stability of soil, water and air.
• Biodiversity in nutrient cycling, pollination, biological control and seed dispersal.
• Biodiversity and aesthetic values.
Answer:
□ Food, Clothing, Shelter, Fuel, Medicines, and Biodiversity
This section highlights the direct utilization of biodiversity by humans.

□ Biodiversity and the Stability of Soil, Water, and Air
This section focuses on the regulatory and life-support services of ecosystems.
Soil Stability:

• Plant Roots bind the soil together, preventing soil erosion by wind and water.
• Decomposers (like earthworms, bacteria, and fungi) enrich the soil by breaking down organic matter, increasing its fertility and water retention capacity.
• Water Stability (Hydrological Cycle):
  • Forests (especially rainforests and hill forests) act as natural sponges, regulating the flow of water. They absorb rainfall, reduce surface runoff, and slowly release water into streams, preventing floods and maintaining water tables.
  • Wetlands filter pollutants from water.
• Air Quality and Stability:
  • Plants (Producers) are responsible for taking in atmospheric Carbon Dioxide (CO₂) and releasing Oxygen (O₂) during photosynthesis, maintaining breathable air quality. Large forest ecosystems help stabilize the global climate by acting as carbon sinks (absorbing CO₂).

□ Biodiversity in Nutrient Cycling, Pollination, Biological Control, and Seed Dispersal These are the essential functional roles (ecosystem services) provided by living organisms.

• Nutrient Cycling (e.g., Carbon Cycle):
  • Decomposers (bacteria and fungi) break down dead organisms, releasing essential nutrients (like nitrogen, phosphorus, and carbon) back into the soil and atmosphere for reuse by plants. This process is crucial for life to continue.
• Pollination:
  • Insects (like bees, butterflies), birds, and bats transfer pollen between plants, enabling reproduction in flowering plants. This is vital for the production of fruits, vegetables, and seeds.
• Biological Control:
  • Nature uses natural predators and parasites to keep pest populations in check, reducing the need for harmful chemical pesticides.
  • Example: Ladybugs eat aphids (plant pests).
• Seed Dispersal:
  • Animals (e.g., birds, squirrels, elephants) eat fruits and carry the seeds elsewhere, often depositing them in fertile soil via their droppings, which helps plants colonize new areas. This is crucial for forest regeneration.

□ Biodiversity and Aesthetic Values
This section discusses the intangible, non-material benefits of biodiversity.

• Aesthetic Appeal: The beauty of nature, including colorful flowers, diverse wildlife, majestic landscapes, and vibrant coral reefs, provides profound sensory and emotional satisfaction.
• Recreation and Ecotourism: Natural areas (national parks, sanctuaries, beaches) are destinations for relaxation, learning, and tourism. This supports local economies.
• Cultural and Spiritual Value: Many indigenous communities and cultures have deep, spiritual connections to specific plants, animals, or natural sites (e.g., sacred groves).
• Education and Research: Biodiversity provides a living laboratory for scientific research, helping us understand genetics, ecology, and evolution.

Textbook Page No : 275
Indicators

Question 14.
From whom does the food chain begin?
Answer:
The food chain begins with Producers (Paddy green plants/algae).

Question 15.
Why are green plants called producers?
Answer:
They are the only organisms capable of producing their own food using solar energy and simple substances through photosynthesis.

Question 16.
Who are the consumers?
Answer:
The consumers are organisms that feed on producers or other consumers. In the example: Rat (Primary), Snake (Secondary), and Eagle (Tertiary).

Question 17.
What is the characteristic of primary consumers?
Answer:
They are herbivores; they feed directly on the producers (green plants).

Question 18.
What is the characteristic of second ary consumer s?
Answer:
They are carnivores or omnivores; they feed on the primary consumers (herbivores).

Question 19.
Who are the tertiary consumers?
Answer:
They are carnivores; they feed on the secondary consumers.

Question 20.
What is the role of decomposers in the food chain?
Answer:
Decomposers (like Bacteria and Fungus) break down the complex organic matter in dead organisms and remains into simpler molecules, returning essential substances and elements to nature. They play a vital role in the flow of matter.

Question 21.
Create a food web using the given organisms

Answer:
The food web starts with the Producers (Trophic Level 1) and shows how energy flows up through the different Consumers.

1. Producers (Trophic Level 1)
Plant: Produces its own food (often including Grass/Paddy/other generic plants as assumed for the ecosystem).

2. Primary Consumers (Trophic Level 2 – Herbivores)
These organisms feed directly on the Plant:

• Deer
• Rabbit
• Rat (Also an Omnivore, but eats seeds/plants)
• Grasshopper
• Squirrel

3. Secondary Consumers (Trophic Level 3 – Primary Carnivores/Omnivores)
These organisms feed on the Primary Consumers:

• Snake: Eats Rat, Frog.
• Fox: Eats Rabbit, Rat, Squirrel, Grasshopper, Frog.
• Frog: Eats Grasshopper.
• Calotes (Lizard): Eats Grasshopper.
• Vulture: Eats dead or dying animals (Scavenger, but occupies this level when eating small, newly dead herbivores).

4. Tertiary Consumers (Trophic Level 4 – Secondary Carnivores)
These organisms feed on Secondary Consumers:

• Tiger: Eats Deer (Primary Consumer) and Fox (Secondary A Tertiary Consumer).
• Fox: Eats Snake, Frog, Calotes.
• Vulture: Eats dead or dying animals (Scavenger, but occupies this level when eating larger, newly dead carnivores like snakes/foxes).

Text Book Page No : 276
Indicators

Question 22.
Trophic level with the maximum number of organisms:
Answer:
Trophic Level 1 (Producers). The base of the pyramid is always the largest.

Question 23.
Trophic level with the least number of organisms.
Answer:
The highest trophic level (e.g., Trophic Level 4, Tertiary Consumers). Energy is lost at each step, supporting fewer organisms at higher levels.

Question 24.
How does the disappearance of top-level organisms affect balance?
Answer:
The disappearance of top predators can lead to an overpopulation of organisms in the lower trophic levels (e.g., secondary consumers). This imbalance can disrupt the entire food web and ecosystem stability (e.g., herbivores might overgraze if their predators disappear).

Text Book Page No : 277

Question 25.
Types of Interactions (Illustration 17.5):

Answer:
Commensalism:
Example: Vanda (orchid) growing on a Tree. (Vanda gets support, tree is unaffected)

Mutualism:
Example: Tree providing nectar to a Butterfly, which helps in pollination. (Lichens are another example).

Competition:
Example: Crop plants and Weeds competing for nutrients and space.

Parasitism:
Example: Flea living on a Dog. (Other examples: intestinal worms, lice).

Predation:
Example: Eagle hunting a Chicken. (Other examples: Tiger hunting deer, Snake eating rat).

Text Book Page No : 278 & 279

Question 26.
Are such relationships necessary to maintain the balance and stability of an ecosystem? Discuss.
Answer:
Yes, ecological relationships are absolutely necessary to maintain the balance and stability of an ecosystem.
They ensure:

Population Control (Predation & Competition): Relationships like predation prevent overpopulation of certain species (prey), which stops them from destroying producers (plants).
Competition limits resource dominance, ensuring diversity.

Energy Flow and Cycling (Food Webs & Decomposers): They facilitate the continuous flow of energy from producers to consumers and the crucial recycling of nutrients (like carbon and nitrogen) back into the soil and atmosphere by decomposers.

Survival and Reproduction (Mutualism): Relationships like mutualism (e.g., pollination) are vital for the reproduction and survival of many plant and animal species.
Essentially, these interdependencies create a resilient web of life; if one part is lost, the entire system can collapse, making these connections essential for ecological balance.

Indicators
Question 27.
The ultimate source of energy in the food chain.
Answer:
The Sun

Question 28.
Storage of solar energy in producers.
Answer:
Plants absorb light and convert it into chemical energy via photosynthesis.

Question 29.
Energy transfer and energy loss.
Answer:
Energy is transferred from one level to the next (Plant → Herbivore → Carnivore). However, a portion is lost as heat at each stage for bodily functions.

Question 30.
Energy availability at different trophic levels.
Answer:
The amount of available energy decreases as you move up the trophic levels.

Question 31.
Which are the important elements and substances among them?
Answer:
The most important elements and substances are the basic building blocks and energy sources of life:
Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and Phosphorus (P).
Substances: Water (H₂O), Proteins, Carbohydrates, and Fats (Lipids).

Text Book Page No : 280
Indicators

Question 32.
In what form is carbon present in the atmosphere?
Answer:
As Carbon dioxide (CO₂).

Question 33.
Why do plants use carbon dioxide?
Answer:
To perform photosynthesis and produce food.

Question 34.
How does carbon dioxide return to the atmosphere?
Answer:
Through the respiration of living organisms, decomposition of dead matter, and combustion (burning) of fossil fuels.

Question 35.
What situations lead to an increase in atmospheric carbon dioxide?
Answer:
Excessive burning of fossil fuels (factories, vehicles) and deforestation (cutting down trees).

Question 36.
How does biodiversity conservation help in maintaining carbon balance?
Answer:
Plants/Forests absorb large amounts of CO₂. Protecting them ensures that CO₂ levels in the atmosphere are regulated.

Question 37.
Collect information and illustrate other material cycles.
Water cycle Nitrogen cycle
Answer:
Water Cycle (Hydrologic Cycle)
Water constantly moves between the Earth and the atmosphere through changes in state.
Evaporation/Transpiration:Water turns into vapor and rises to the atmosphere.
Condensation: Vapor cools and forms clouds.
Precipitation: Water falls back as rain, snow, etc.
Runoff/Infiltration: Water flows over or soaks into the ground.
Nitrogen Cycle
Nitrogen is converted into usable forms by bacteria for living things.
Nitrogen Fixation: Bacteria convert atmospheric Nitrogen gas (N₂) into Ammonia (usable form).
Assimilation: Plants absorb this nitrogen to make proteins/DNA.
Nitrification: Bacteria convert Ammonia to Nitrates (preferred plant food).
Denitrification: Other bacteria return nitrogen compounds back to Nitrogen gas (N₂) in the atmosphere.

Text Book Page No : 281
Indicators

Question 38.
What would happen if decomposers disappeared?

Answer:
Fig 17.6 shows a dense, healthy forest. Fig 17.7 shows a developed city area where the forest has been destroyed.

Question 39.
How does deforestation affect other living beings?
Answer:
It destroys habitats, causing food scarcity and death for wild animals, leading to species extinction.

Question 40.
Are all the organisms that once lived in your area still seen today?
Answer:
No. Many organisms have disappeared (become locally extinct or extirpated) due mainly to habitat loss and pollution.

Question 41.
Is biodiversity in our area increasing or decreasing?
Answer:
Decreasing. In most regions, the expansion of human settlements and activities leads to biodiversity depletion (loss of species and ecosystems).

Question 42.
Is this kind of biodiversity loss happening only in our region?
Answer:
No. It is a global phenomenon that is happening all over the world. The crisis is tracked globally by organizations like IUCN.

Text Book Page No : 282 & 283

Question 43.
Can we protect all species at all times?
Answer:
No. While the goal is protection, limited resources and changing environments mean conservation efforts often prioritize rare and endangered species (like those in the Red Data Book).

Question 44.
Is it possible to fulfill human needs and conserve biodiversity at the same time?
Answer:
Yes. It requires careful planning and implementation of conservation strategies, such as In-situ conservation (protecting natural habitats) and Ex-situ conservation (protecting species outside their habitat).

Question 45.
What are the reasons for wild animals to enter human settlements?
Answer:
The main reasons are the depletion of resources and loss of habitat within the forest. For example, intensifying summer heat can drive animals like elephants into settlements in search of food and water.

Question 46.
Can you suggest any solutions to this problem?
Answer:
Using Al technology to generate sounds to drive wild animals back into the forest.
Preparing special sanctuaries or shelters outside the forest to house animals like tigers.
Providing adequate compensation to farmers for crop damage.

Question 47.
Why is it necessary to conserve biodiversity?
Answer:
Biodiversity is necessary because it ensures human survival by providing:

• Food (fruits, vegetables, fish, etc.).
• Medicine (many modern medicines are made from plants and other organisms).
• Ecosystem Services (creatures like bees help in pollination).
• Clean Air and overall environmental health.

Question 48.
What are the organizations in our country that work for nature conservation?
Answer:
There are various government institutions, schemes, and local bodies that work for conservation:

• Kerala State Biodiversity Board
• Biodiversity Management Committees (BMC) at the local self-government level, which prepare the People’s Biodiversity Register (PBR).
• (Internationally, WWF and IUCN are mentioned as examples).

Class 8 Basic Science Chapter 17 Question Answer Extended Activities

Question 1.
Examine the People’s Biodiversity Register (PBR) of the local self-government body (Panchayat/Municipality / Corporation) where your school is located. List the species found under each category and their current status (increasing/decreasing). Present your findings in the class.

Question 2.
Plant at least 10 different types of plants at your home and make a small garden. Before making your garden, record the organisms that were already present and the composition of the soil. After one month of planting, observe and record the changes that occurred. Present your findings and conclusions in the class.

The Beauty of Diversity Class 8 Notes

Class 8 Basic Science The Beauty of Diversity Notes Kerala Syllabus

Introduction: Biodiversity

• Biodiversity Park: A place (like in a school) that showcases a variety of living organisms, both plants and animals, in their natural setting. It’s called a biodiversity park because it contains diverse life forms.
• Biodiversity: Refers to the vast variety of life forms found on Earth, including plants, animals, fungi, microorganisms, etc.

ജീവവൈവിധ്യം (Biodiversity) എന്നാൽ ഭൂമിയി ലുള്ള വിവിധ തരത്തിലുള്ള ജീവജാലങ്ങൾ (സസ്യ ങ്ങൾ, ജന്തുക്കൾ, സൂക്ഷ്മജീവികൾ) എന്നാണ് അർത്ഥമാക്കുന്നത്. ഒരു ജൈവവൈവിധ്യ പാർക്ക് (Biodiversity Park) എന്നാൽ ഇത്തരത്തിലുള്ള വിവിധ ജീവജാലങ്ങളെ ഒരുമിച്ച് കാണാൻ കഴി യുന്ന ഒരിടമാണ്.

Habitat(ആവാസവ്യവസ്ഥ)

• The natural surroundings where each living being lives is called its habitat.
• Examples of Habitats (Fig 17.3):

• • Coral reef (പവിഴപ്പുറ്റ്)
  • Mangrove Forest (കണ്ടൽക്കാട്)
  • Desert (മരുഭൂമി)
  • Wetlands (തണ്ണീർത്തടം)
• Habitat Examples (Fig 17.2):

• • Hibiscus Plant: Land
  • Fish: Water (Ocean/Sea)
  • Frog: Land and Water (Amphibious)
  • Polar Bear: Polar regions (Snow/Ice)

ഓരോ ജീവിയും സ്വാഭാവികമായി ജീവിക്കുന്ന ചുറ്റുപാടിനെയാണ് അതിന്റെ ആവാസവ്യവസ്ഥ (Habitat) എന്ന് പറയുന്നത്. കര, ജലം, മരുഭൂമി, ധ്രുവപ്രദേശങ്ങൾ എന്നിവയെല്ലാം വിവിധതരം ആവാസവ്യവസ്ഥകളാണ്.

Lichens (ലൈക്കനുകൾ)
Lichens are an example of a symbiotic relationship and contribute to biodiversity.

• Structure: Some algae or cyanobacteria live inside certain fungi.
• Symbiosis (സഹജീവനം): This is a mutually beneficial relationship.
  • The fungus provides structure and protection.
  • The algae or cyanobacteria produce food for both organisms through photosynthesis.
• The symbiotic organisation of these organisms is known as lichens.

ലൈക്കനുകൾ എന്നത് ഫംഗസുകളും ആൽഗകളും (അല്ലെങ്കിൽ സയനോബാക്ടീരിയകളും ഒരുമിച്ച് ജീവിക്കുന്ന ഒരു കൂട്ടായ്മയാണ്. ഫംഗസ് സംര ക്ഷണവും ഘടനയും നൽകുമ്പോൾ, ആൽഗകൾ പ്രകാശസംശ്ലേഷണം (photsoynthesis) വഴി രണ്ടുപേർക്കും വേണ്ട ആഹാരം നിർമ്മിക്കുന്നു. ഇത് സഹജീവനത്തിന് (symbiosis) ഒരു ഉദാഹ രണമാണ്.

Biodiversity (ജീവവൈവിധ്യം)
Biodiversity refers to all the diverse living organisms on Earth, including plants, animals, and microorganisms, along with their habitats.

• Operational Definition: “All the diverse living organisms on Earth, including plants, animals, and microorganisms, along with their habitats, together form biodiversity.”
• Variation: Even within a single species, variations can exist (e.g., different colours of hibiscus flowers, different types of ants – Fig 17.4).
  There are over 15,000 types of ants discovered, adapted to various habitats like deserts, rainforests, and mountains.

Levels of Biodiversity (ജീവവൈവിധ്യത്തിന്റെ തലങ്ങൾ)
Biodiversity can be studied at different levels (Illustration 17.1):

• Genetic Diversity (ജനിതക വൈവിധ്യം):
  • Variation within a species.
  • Example: Different varieties of rice (over 50,000 in India) or mangoes (over 1,000 varieties in India) show genetic diversity. Different breeds of dogs or different colours of hibiscus flowers also represent this.
• Species Diversity (സ്പീഷീസ് വൈവിധ്യം):
  • Species-level diversity; the variety of different species within a particular area or habitat.
  • Example: In a forest, there are elephants, monkeys, birds, snakes, grasses. bacteria, etc. – all different species living together.
• Ecosystem Diversity (ആവാസവ്യവസ്ഥാ വൈവിധ്യം):
  • Diversity at the ecosystem level; the variety of different habitats or ecosystems within a larger region.
  • Example: In a village, there might be paddy fields, coconut groves, hills, rivers, and marshes – each representing a different ecosystem. Coral reefs, mangrove forests, deserts, and wetlands are also examples of different ecosystems.

ജീവവൈവിധ്യത്തെ മൂന്ന് തലങ്ങളിൽ പഠിക്കാം:

• ജനിതക വൈവിധ്യം: ഒരു സ്പീഷീസിനുള്ളി ലെ വ്യതിയാനങ്ങൾ (ഉദാ: വിവിധയിനം നെല്ലുകൾ, മാവുകൾ).
• സ്പീഷീസ് വൈവിധ്യം: ഒരു പ്രദേശത്തുള്ള വ്യത്യസ്ത സ്പീഷീസുകളുടെ എണ്ണം (ഉദാ: കാട്ടിലെ ആന, കുരങ്ങ്, പാമ്പ് തുടങ്ങിയവ).
• ആവാസവ്യവസ്ഥാ വൈവിധ്യം: ഒരു വലിയ പ്രദേശത്തെ വിവിധതരം ആവാസവ്യവസ്ഥ കൾ (ഉദാ: വയൽ, കാവ്, പുഴ, കുളം എന്നിവ ചേർന്ന ഒരു ഗ്രാമം).

Importance of Biodiversity (ജീവവൈവിധ്യത്തിന്റെ പ്രാധാന്യം)
Biodiversity plays a crucial role in the survival of all living beings, including humans.
The theme “Our biodiversity, our food, our health” highlights this connection.

• Benefits / Roles of Biodiversity:
  • Provisioning Services: Provides essential resources like food, clothing, shelter, fuel, and medicines.
  • Regulating Services: Helps maintain the stability of soil, water, and air; plays a role in nutrient cycling (e.g., decomposition), pollination (പരാഗണം), biological control (ജൈവീക കീടനിയന്ത്രണം), and seed dispersal (വിത്ത് വിതരണം).
  • Supporting Services: Essential for processes like photosynthesis and soil formation.
  • Cultural & Aesthetic Values: Provides recreational opportunities, beauty, and inspiration.
• May 22 is celebrated as the International Day for Biodiversity.

Biodiversity and the Balance of the Eco system (ജീവവൈവിധ്യവും ആവാസവ്യവസ്ഥയുടെ സന്തുലനവും)
The interactions between different organisms are crucial for maintaining the balance and stability of an ecosystem. One key interaction is the flow of energy through feeding relationships, represented by food chains and food webs.

• Food Chain (ഭക്ഷ്യ ശൃംഖല)
  • A representation of how energy flows through an ecosystem, showing who eats whom.
  • Example (Illustration 17.3): Paddy → Rat → Snake → Eagle.

• • Components of a Food Chain (based on Indicators):
• Producers (ഉൽപ്പാദകർ):
  • Food chains begin with Producers.
  • Green plants are called producers because they produce their own food using sunlight (photosynthesis). They form the base of most food chains, (e.g., Paddy).
• Consumers (ഉപഭോക്താക്കൾ):
  • Organisms that obtain energy by feeding on other organisms.
  • Primary Consumers (പ്രാഥമിക ഉപഭോ ക്താക്കൾ): Herbivores that feed directly on producers (plants), (e.g., Rat eating paddy).
• Secondary Consumers ((ദ്വിതീയ ഉപഭോ ക്താക്കൾ):) Carnivores or omnivores that feed on primary consumers, (e.g., Snake eating rat).
• Tertiary Consumers (തൃതീയ ഉപഭോക്താക്കൾ): Carnivores or omnivores that feed on secondary consumers, (e.g., Eagle eating snake).
• Decomposers (വിഘാടകർ)::
  • Bacteria, fungi, and other organisms that break down complex molecules in dead bodies and other organic remains into simpler molecules.
  • Role: They return essential nutrients back to nature (soil, water, air), making them available for producers again, (e.g., Bacteria, Fungus).
• Food Web (ഭക്ഷ്യ ശൃംഖലാജാലം)
  • A network of interconnected food chains found in an ecosystem. Most organisms eat more than one type of food and are eaten by more than one type of predator.

Trophic Level (പോഷണ തലം)

• The position an organism occupies in a food chain is called a trophic level.

Trophic Level 1 : Producers (Plants).
Trophic Level 2 : Primary Consumers (Herbivores feeding directly on plants).
Trophic Level 3 : Secondary Consumers (Carnivores/Omnivores feeding on herbivores).
Trophic Level 4 : Tertiary Consumers (Carnivores/Omnivores feeding on secondary consumers).

• Complexity: As food webs become complex, a single organism can belong to different trophic levels depending on what it eats.

Ecological Interactions (പാരിസ്ഥിതിക ബന്ധങ്ങൾ)
Organisms in an ecosystem interact in various ways besides just eating each other. These relationships are necessary to maintain the balance and stability of the ecosystem.

Types of Interactions (Illustration 17.5):

• Commensalism:
  • Beneficial to one organism, neither beneficial nor harmful to the other.
  • Example: Vanda (orchid) growing on a Tree. (Vanda gets support, tree is unaffected).
• Mutualism:
  • Beneficial to both organisms.
  • Example: Tree providing nectar to a Butterfly, which helps in pollination. (Lichens are another example).
• Competition:
  • At first, harmful to both (as they compete for the same limited resources like sunlight, water, food); later, benefit for the winner.
  • Example: Crop plants and Weeds competing for nutrients and space.
• Parasitism:
  • Beneficial to one (the parasite), harmful to the other (the host). The parasite depends on the host for food.
  • Example: Flea living on a Dog. (Other examples: intestinal worms, lice).
• Predation:
  • Beneficial to one (the predator), harmful to the other (the prey). The prey becomes food for the predator.
  • Example: Eagle hunting a Chicken. (Other examples: Tiger hunting deer, Snake eating rat).

Energy Flow in an Ecosystem (ഊർജ്ജപ്രവാഹം ആവാസവ്യവസ്ഥയിൽ)
Energy is needed for all bodily functions and is transferred from one trophic level to the next in a food chain.

Role of Decomposers: Decomposers break down dead organic matter, releasing energy, but primarily returning nutrients (matter) to the ecosystem.

Flow of Matter in an Ecosystem (പദാർത്ഥങ്ങളുടെ ചാക്രിക പ്രവാഹം)
Various substances and elements are needed for life and must be cycled through the ecosystem. For ecosystems and biodiversity to survive, the flow of matter and energy must take place effectively. Substances absorbed from the non-living environment circulate through living organisms and return to where they came from. Food chains, biodiversity, and decomposers play vital roles in this.

Carbon Cycle (കാർബൺ ചകം)
Plants use atmospheric carbon dioxide for photosynthesis. Carbon returns to the atmosphere through respiration, decomposition, and combustion of fossil fuels.

• Atmospheric Carbon: Carbon exists in the atmosphere primarily as Carbon dioxide (CO₂).
• Photosynthesis: Plants absorb CO₂ and convert it into chemical energy (organic compounds).
• Respiration & Decomposition: Carbon returns to the atmosphere through the respiration of living organisms and the decomposition of dead matter.
• Combustion: Burning fossil fuels also releases CO₂ back into the atmosphere.
• Conservation: Conserving biodiversity helps maintain the carbon balance in ecosystems.

Biodiversity Depletion (ജീവവൈവിധ്യ ശോഷണം)
Human activities can severely damage eco-systems and lead to a loss of biodiversity.
Habitat Loss:

• Deforestation and human activities destroy natural habitats, forcing wild animals into human settlements.
• Pictures in the text contrast a natural forest with an industrialized/deforested area to highlight habitat destruction.
  • Human-Wildlife Conflict:
    Wild animals (like elephants and tigers) enter farmlands and settlements due to food scarcity and habitat loss, causing agricultural loss and danger to humans.
  • Technological Solution: Al technology is being used to detect animals via cameras and generate specific sounds to drive them back into the forest.
  • Unique Species:
    Purple Frog (Mahabali Frog): A rare frog that lives underground and surfaces only once a year to mate. It is called a “living fossil” because it has undergone very little evolutionary change since the time of the dinosaurs.

The Red Data Book:

• Publisher: IUCN (International Union for Conservation of Nature).
• Purpose: It contains information about rare and endangered plants and animals.
• Listed Species Examples: Malabar civet cat, Ganges Shark, Kashmir stag, Rameswaram Parachute spider, Lion-tailed macaque, and Nilgiri tahr.

• Importance of Conservation:
  • Biodiversity is essential for food, clean air, pollination, and medicines.
  • Medicinal Plants: Many modern medicines are derived from plants. Even plants considered “weeds” may have medicinal value.
• Conservation Organizations:
  • International: IUCN, WWF (World Wide Fund for Nature).

• • Local: Kerala State Biodiversity Board.

Methods of Biodiversity Conservation
Conservation is classified into two main types:

• In-situ Conservation
  Protection of organisms within their natural habitats.
  • National Parks: e.g., Eravikulam, Silent Valley.
  • Wildlife Sanctuaries: e.g., Periyar.
  • Biosphere Reserves: e.g., Nilgiri.
  • Community Reserves: e.g., Kadalundi.
  • Ecological Flotspots: e.g., Western Ghats, Himalayas.
• □ Ex-situ Conservation
  Protection of organisms outside their natural habitats in controlled environments.
  • Examples: Botanical gardens, Zoological gardens, Gene banks, Aquariums.

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 16 Tree of Life Important Questions ensure conceptual clarity.

Tree of Life Extra Questions and Answers Class 8 Basic Science Chapter 16 Kerala Syllabus

Tree of Life Class 8 Important Questions

Question 1.
Characteristics of Kingdom Fungi are given below. Choose the correct option.
i. They are Prokaryotes.
ii. They have a cell wall made of chitin.
iii. They are autotrophs containing chlorophyll.
iv. They are saprophytes.
(a) i, iii correct
(b) ii, iv correct
(c) i, ii, iv correct
(d) All are correct
Answer:
(b) ii, iv correct

Question 2.
Rules of Binomial Nomenclature developed by Carl Linnaeus are given. Choose the correct statements.
i. The scientific name has two parts: species name first, genus name second.
ii. The first letter of the Genus name should be capital.
iii. The first letter of the Species name should be capital.
iv. The scientific name should be printed in italics or underlined if handwritten.
(a) i, ii, iii correct
(b) ii, iv correct
(c) i, iv correct
(d) All are correct
Answer:
(b) ii, iv correct

Question 3.
Which of the following statements correctly define a ‘Species’ according to the biological concept?
i. It is the most basic level of classification.
ii. Organisms within a species look exactly identical.
iii. Members of a species can naturally reproduce to form fertile offspring.
iv. It is the level just below Kingdom in classification.
(a) i, iii correct
(b) i, ii, iii correct
(c) iii, iv correct
(d) i only correct
Answer:
(a) i, iii correct

Question 4.
Complete the missing levels in the hierarchical classification system shown below.
Kingdom → Phylum → (a) _______ → Order → (b) ________ → Genus → (c) ________
Answer:
a) Class b) Family c) Species

Question 5.
Complete the following table summarizing characteristics of the Five Kingdoms.

Kingdom	Nuclear Type (Prokaryotic/Eukaryotic)	Mode of Nutrition (Autotroph/Heterotroph/ Saprotroph	Example
Monera	(a) ………………….	Autotroph or Heterotroph	Bacteria
Fungi	Eukaryotic	(b) ………………….	Yeast
Plantae	Eukaryotic	(c) ………………….	Coconut Tree

Answer:

Kingdom	Nuclear Type (Prokaryotic/Eukaryotic)	Mode of Nutrition (Autotroph/Heterotroph/ Saprotroph	Example
Monera	(a) Prokaryotic	Autotroph or Heterotroph	Bacteria
Fungi	Eukaryotic	(b) Saprotroph	Yeast
Plantae	Eukaryotic	(c) Autotroph	Coconut Tree

Question 6.
Fill in the missing classification levels for the Tiger (Panthera tigris).

Level	Taxon
Kingdom	Animalia
Phylum	Chordata
Class	(a) …………………….
Order	Carnivora
Family	(b)  …………………….
Genus	Panthera
Species	(c)  …………………….

Answer:
a) Mammalia,
b) Felidae,
(c) tigris

Question 7.
Who introduced the Five-Kingdom classification system, and what were the five kingdoms proposed?
Answer:
Robert H. Whittaker introduced the Five-Kingdom classification. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

Question 8.
What is Taxonomy?
Answer:
Taxonomy is the branch of science that deals with classifying organisms by comparing their characteristics, identifying similarities and differences, and giving them scientific names.

Question 9.
What contribution did John Ray make to the field of classification?
Answer:
John Ray initiated the scientific method of classification and was the first to use the term ‘species’.

Question 10.
Explain the need for a universally accepted scientific naming system like Binomial Nomenclature.
Answer:
The same organism often has different common names in different regions or languages (e.g., Papaya). This creates confusion and makes it difficult to accurately identify and study organisms globally. Binomial Nomenclature provides a unique, two-part scientific name (Genus and species) that is universally accepted, overcoming language barriers and ensuring clarity in scientific communication.

Question 11.
Why was Kingdom Monera split into two separate kingdoms (Archaebacteria and Eubacteria) in the Six-Kingdom classification?
Answer:
The split was proposed by Carl Woese based on modern scientific observations, particularly differences at the molecular level (like genetics and cell wall composition) which indicated that the organisms originally grouped in Monera actually represented two very distinct and ancient lineages of prokaryotes.

Question 12.
Explain the main limitation of classifying organisms based only on their external structure, as was done in early classification systems.
Answer:
Classifying based only on external structure can be misleading because organisms that look similar externally may not be closely related evolutionarily or genetically (like Wolffia and Salvinia). Conversely, organisms that look

different might be closely related. Modern classification uses evolutionary and genetic data along with morphology for a more accurate system.

Question 13.
Identify the organism that belongs to Kingdom Monera from the following list: Amoeba, Yeast, Paramecium, Bacteria.
Answer:
Bacteria. (Amoeba and Paramecium are Protista; Yeast is Fungi).

Question 14.
Find the odd one out based on the Five-Kingdom classification: Mushroom, Mould, Yeast, Euglena.
Answer:
Euglena.
Reason: Mushroom, Mould, and Yeast belong to Kingdom Fungi. Euglena belongs to Kingdom Protista.

Question 15.
Which of the following is NOT an example of a species? Human beings, Cats, Mammalia, Coconut Tree.
Answer:
Mammalia.
Reason: Human beings (Homo sapiens), Cats (Felis catus), and Coconut Tree (Cocos nucifera) represent specific species. Mammalia is a Class, a higher level of classification that includes many different species.

Question 16.
Analyse the statement and answer the questions.
The scientific name of dog is Canis familiaris
a. How is this method of giving scientific names to organisms known as?
b. What does the words Canis and familiaris in the scientific name indicate?
Answer:
a. Binomial nomenclature
b. Canis indicates the name of the genus and the ‘familiaris’ indicates the name of the species.

Question 17.
Cocos nucifera is the scientific name of coconut. Identify the level of classification indicated by the underlined part.
Answer:
Genus

Question 18.
The various levels of classification of human beings based on the six kingdom classification are given below. Complete the table suitably.

Domain	Eukarya
Kingdom	a. ________
Phylum	Chordata
Class	b. ________
Order	Primates
Family	Hominidae
Genus	c. ________
Species	d. ________

Answer:
a. Animalia
b. Mammalia
c. Homo
d. Sapiens

Question 19.
Find the correct pair from the following.
i. Robert Hooke-Discovered the centre of the cell
ii. Robert H Whittaker – 5 Kingdom classification
iii. M. J. Schleiden – Found animal body is made up of cells
Answer:
ii. Robert. H. Whittaker – 5 kingdom classification

Question 20.
Analyse the statement and answer the following questions.
According to the Binomial nomenclature, scientific name of human being is Homo sapiens.
a) What does the First word Homo indicate
b) Who proposed the Binomial nomenclature?
c) What is the merit of Binomial nomenclature?
Answer:
a) Genus

b) Carl Linnaeus

c) Each organism is known by different names in different places and in different languages. So a commonly acepted name is needed for identifying organisms.

Question 21.
Identify the relation between the words of first pair and complete the second pair suitably
a) Mushroom: Fungi
Amoeba: …………………….
b) Cat: Felis domesticus
Crow: ……………………
Answer:
a. Protista
b. Corvus splendens

Question 22.
Rewrite the following sentences correctly. If there is any error in the underlined part
a. Aristotle is known as the father of Botany
b. Monera includes unicellular organisms with distinct nucleus
c. Five Kingdom classification was introduced by Robert H Whitaker
Answer:
a. Theophrastus is known as the father of Botany
b. Protista includes unicellular organisms with distinct nucleus

Question 23.
Name of two scientists related to taxonomy is given below. Write their contributions in this field.
i) Charakan
ii) John Ray
Answer:
a. Charakan Wrote the treatise ‘Charakasamhita1 including around 200 plants and animals.
b. John Ray Recorded more than 18000 plants in his book named Historia generalis plantarum’ Used the term ‘species’ for the first time.

Question 24.
The scientific name of Tiger is Panthera Tigris.
a. What do the words ’Panthera’ and ’Tigris’ indicate ?
b. What are the advantages of giving scientific name to organisms?
c. Name the scientist who proposed the scientific naming of organisms?
Answer:
a. Panthera indicates Genus and Tigris indicates Species

b. By giving scientific name, organisms can be easily identified all over the world and it helps to solve the difficulties arising out of an organisms known by various names in different languages and regions.

c. Carl Linnaeus

Question 25.
Write the taxonomic hierarchy of coconut tree by choosing appropriate terms from the box
Plantae cocos Series
Nucifera Dicotyledonae
Genus Monocotyledonae

Domain	Eukarya
Kingdom	i. ……………………..
Phylum	Angiospermophyta
Class	ii. ……………………
iii. ……………………	Calysinae
Family	Aracasiae
iv. ………………………	v. ……………………
Species	vi. ………………….

Answer:
i. Plantae
ii. Monocotyledonae
iii. Order
iv. Genus
v. Cocos
vi. Nucifera

Question 26.
Correct the mistakes if any in the underlined part.
a. Taxonomic keys are the scientific indicators used for identifying and classifying plants and animals.
b. Genus is the basic level of classification.
c. The first word of the scientific name indicates the genus and the second word indicates the species.
Answer:
Species is the basic level of classification

Question 27.
Name of scientists who contributed in the field of taxonomy are given below. Identify their contribution which is given in the box and make pairs.
A) Carl Woese
B) John Ray
C) Theophrastus
d) R.H. Whittaker
i. Classified the organisms as those with red blood cells and those without red blood cells.
ii. Classified plants into annuals, biennials and perennials.
iii. Six kingdom classification.
iv. Five kingdom classification.
v. Used the term species for the first time
Answer:
i. Aristotle
ii. Theophrastus
iii. Cari woese
iv. Robert H Whittaker
v). John ray

Question 28.
Identify the word pair relation and fill the blanks.
a. 2 Kingdom classification:
Carls Linnaeus :: 5 kingdom
Classification: ………………………….
b. Mushrooms: Fungi::
Bacteria: ………………………….
c. Aristotle – Father of Biology
Carls Linnaeus – ………………………….
d. Golden shower : Cassia fistula
:: ………………………….: Corvus splendens
e. Charaka: Father of Ayurveda
:: ………………………….: Father of Botany
Answer:
a. R H Whittaker
b. Monera
c. Father of Taxonomy
d. Crow
e. Theophrastus

Question 29.
Identify the odd one and write the characteristic features of others.
a. Lion, Tiger, Rabbit, Cat.
b. Genus, Order, Carl Linnaeus, Phylum.
Answer:
a. Rabbit – Others including order Carnivora
b. Carl Linnaeus – He is the Father of Modern Taxonomy. Others are different levels of classification.

Question 30.
Which organism is most suitable for the following indicators (amoeba, bacteria, virus, Fungus)
• Lives only in living cell
• Pathogen
• Only genetic material and a protein covering.
Answer:
Virus

Question 31.
Find out the scientists suitable to the statements given.
i. Author of Charaka Samhitha
ii. Author of Historia Generalis Plantarum
iii. Father of Modern Taxonomy
iv. Father of Biology
Answer:
i. Charaka
ii. John ray
iii. Carl Linnaeus
iv. Aristotle

Question 32.
Complete the table
Organism Scientific Name
Elephant ……………………..
Peacock ……………………..
Dog ……………………..
Hibiscus ……………………..
Neem ……………………..
Paddy
……………………..
Answer:
Elephas Maximus / Elephas Indicus
• Pavo Cristatus
• Canis Familiaris
• Hibiscus Rosasinensis
• Azadirachta Indica
• Oryza sativa

Question 33.
What are limitations in the system of classification of Carl Linnaeus.
Answer:
Some lower organisms share the characters of both animals and plants. So it is difficult to recognize them as plants or animals. Linnaeus considered only plants and animals for his classification. Microscopic organisms like bacteria, fungus, protozoa etc were not included either in plant kingdom or in animal kingdom. Certain animals which were included in the classification of Linnaeus shows characters of both the animal and plant kingdoms. Eg: Euglena protozoan shows locomotory movements like animals, but it contains chlorophyll like plants.

Question 34.
Hints about some organisms are given below. Name the kingdom to which these organisms belong.
a. Multicelluar heterotropic organisms with a nucleus and capacity for locomotion.
b. Multicelluar heterotropic, nonmotile organisms with a nucleus.
c. Unicelluar organisms with a nucelus.
d. Multicelluar, autotropic, nonmotile organisms with a nucleus.
Answer:
a. Animalia
b. Fungi
c. Protista
d. Plantae

Question 35.
Write the scientific name of following animals and plants.
Coconut, paddy, wheat, crow, mango, grapes
Answer:
Coconut – Cocos nucifera
Paddy – Oryza sativa
Wheat – Triticum aestivum
Crow – Corvus splendens
Mango – Mangifera indica
Grapes – Vitis vinifera

Question 36.
What are two important characters of species?
Answer:

1. Species is a group of organisms that can freely interbreed to produce fertile offsprings.
2. A group of organisms that closely resemble each other in structure biochemical make up and external charecteristics but which are genetically different. In one species there may be sub species.

Question 37.
“The method of classification adopted by Whittakar is much better than the method adopted by Carl Linnaeus the father of the science of classification. What is your response to this statement?
Answer:
The classification of Linnaeus had only two kingdom, plants and animals. He did not consider bacteria, protozoa, fungus etc. Certain characters of animals considered by Linnaeus for classification are found in both the kingdoms, eg. photosynthesis found in plants is seen in some animals like Euglena.

Certain characters of animals can be seen in plants also, eg certain types of algea. But Whittakar adopted the method of having five kingdoms including protozoa and bacteria.

1. Monera,
2. protista
3. fungi
4. plantae
5. animalia

Question 38.
Bacteria does not have a well defined Nucleus. Viruses are also like Bacteria. Why is it not possible to include viruses under Monera.
Answer:
Viruses exhibit living nature only when they enter the host cells. On other occasions they do not exhibit living nature. But organisms in Monera are not like that.

Question 39.
How do the levels of classification of plants made by Carl Linnaeus differ from the levels of classification of Animals?
Answer:
Not much differences are there. In the place of ‘Order’ in animal classification, plant classification has series. And in the place of ‘Phylum’ in animal classification. plant classification has ‘Division’.

Question 40.
Cell is the smallest unit of life. But there are certain organisms that live without cell too. Analyse these statement.
Answer:
Life is not possible without a cell. Viruses do not have cells. As it is so, it does not have life when it outside a living cell. As it enters a living cell, it will show the features of life forms. It makes use of the components of the host cell and continues to live. Though it does not have a cell, it can continue its life only after entering a host cell and by making use of its components.

Question 41.
Observe the given statement, and write correct answer if you find false statements.
a. Aristotle is the Father of Biology.
b. John Ray is the Father of Botany.
c. Carl Linnaeus used the term ‘species’ for the first time
d. Charakan proposed binomial nomenclature.
Answer:
a. True
b. False, Theophrastus
c. False, John Ray
d. False, Carl Linnaeus.

Question 42.
Read the following statements and choose the correct option:
Statement I: John Ray was the first scientist to use the term ‘species’.
Statement II: Aristotle classified organisms into five kingdoms.
A) Both Statements are true.
B) Statement I is true, but Statement II is false.
C) Statement I is false, but Statement II is true.
D) Both Statements are false.
Answer:
B) Statement I is true, but Statement II is false. : Explanation: John Ray used the term species (True). Aristotle classified animals by red blood, not 5 kingdoms 9. (Whittaker did that).

Question 43.
Read the following statements regarding classification levels:
Statement I: The level just below Kingdom is Phylum.
Statement II: Species is the basic and smallest unit of classification.
A) Both Statements are correct.
B) Only Statement I is correct.
C) Only Statement II is correct.
D) Both Statements are incorrect.
Answer:
A) Both Statements are correct. : Explanation: Phylum is below Kingdom, and Species is the basic unit. Both are correct.

Question 44.
Assertion (A): According to modern classification, Wolffia and Anthurium are included in the same family, Araceae.
Reason (R): Wolffia and Anthurium look exactly the same in their external structure.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is NOT the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
Answer:
C) A is true, but R is false. : Explanation: They are in the same family due to genetic/evolutionary relationships, despite having different external structures.

Question 45.
Assertion (A): Fungi like mushrooms cannot perform photosynthesis.
Reason (R): Fungi cells lack chlorophyll and are saprophytes.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is NOT the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
Answer:
A) Both A and R are true, and R is the correct explanation of A. : Explanation: Fungi are saprophytes because they lack chlorophyll.

Question 46.
Who introduced the method of Binomial Nomenclature?
A) Robert H. Whittaker
B) Carl Woese
C) Carl Linnaeus
D) Ernst Haeckel
Answer:
(C) Carl Linnaeus

Question 47.
Which of the following organisms belongs to Kingdom Monera?
A) Amoeba
B) Bacteria
C) Mushroom
D) Coconut tree
Answer:
(B) Bacteria

Question 48.
Write the scientific names of the following organisms:
a) Human
b) Tiger
Answer:
a) Human: Homo sapiens
b) Tiger: Panthera tigris

Question 49.
List any two rules that must be followed while writing scientific names (Binomial Nomenclature).
Answer:
Rules of Binomial Nomenclature:
1. The first word is the Genus (starts with a Capital letter).
2. The second word is the Species (starts with a small letter).
(Optional: The name should be in italics).

Question 50.
Why was the Two-Kingdom classification system proposed by Carl Linnaeus considered insufficient? Give one reason.
Answer:
It was insufficient because it did not classify organisms like bacteria, fungi, and some unicellular organisms correctly. For example, Fungi are neither plants (no photosynthesis) nor animals, yet they had to be forced into one of the two groups.

Question 51.
Differentiate between Kingdom Monera and Kingdom Protista based on their cell structure (nucleus) and give one example for each.
Answer:
Monera: Prokaryotes (do not have a distinct nucleus). Example: Bacteria. Protista: Eukaryotes (have a distinct nucleus). Example: Amoeba.

Question 52.
Complete the table below regarding the classification of the Tiger:

Level	Name
Kingdom	Animalia
Phylum	(a) ……………….
Class	Mammalia
Order	(b) ……………….
Family	Felidae
Genus	(c) ……………….

Answer:
(a) Chordata
(b) Carnivora
(c) Panthera

Question 53.
Explain the Six-Kingdom Classification system. Who proposed it, and how was the Kingdom Monera divided in this system?
Answer:
Proposed by: Carl Woese.

Explanation: He analyzed the Kingdom Monera and found significant differences among its members. He divided Monera into two separate kingdoms: Archaebacteria and Eubacteria. This, along with Protista, Fungi, Plantae, and Animalia, makes up the six kingdoms.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 16 Chemistry of Matter Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 16 Chemistry of Matter Question Answer Notes

Class 8 Basic Science Chapter 16 Notes Kerala Syllabus Chemistry of Matter Question Answer

Chemistry of Matter Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Examine the following passage and correct the errors if any, found in the underlined parts.
Classifying living beings into larger groups based on similarities and further into smaller groups based on differences is the basis of the cell theory. The various levels of classification were developed by Theophrastus. He is known as the Father of Taxonomy. The smallest unit in classification is phylum. The method of scientifically naming organisms was developed by Carl Linnaeus. The practice of identifying an organism by using both its genus and species name is known as taxon. According to this, when writing the scientific name of an organism, the species name should be written first.
Answer:

Original Underlined Text	Correction and Reason
…is the basis of the cell theory	Correction: Taxonomy or Classification. Classification is the basis for grouping organisms.
The various levels of classification were developed by Theophrastus	Correction: Carl Linnaeus. Linnaeus ‘ introduced the different levels of classification.
The smallest unit in classification is phylum	Correction: Species. Species is the most basic/smallest level of classification.
..practice of identifying an organism by using both its genus and species name is known as taxon	Correction: Binomial Nomenclature. Taxon refers to the classification levels themselves (like Kingdom, Phylum, etc.).
…the species name should be written first	Correction: Genus name. The genus name comes first, and the species name comes second in Binomial Nomenclature.

Question 2.
Match the following.

A	B
1. John Ray	a) Living things were classified into 5 kingdoms
2. Carl Linnaeus	b) Plants were classified as trees, shrubs, and herbs
3. Ernst Haeckel	c) Living things were classified into 3 kingdoms
4. Robert H. Whittaker	d) Father of taxonomy
5. Aristotle	e) Initiated the scientific method of classification
	f) Animals were classified into those with red blood and those without red blood.

Example: Aristotle classified animals into two groups – those with red blood and those without red blood.
Answer:
1. John Ray – e) Initiated the scientific method of classification
2. Carl Linnaeus – d) Father of taxonomy
3. Ernst Haeckel – c) Living things were classified into 3 kingdoms
4. Robert H. Whittaker – a) Living things were classified into 5 kingdoms
5. Aristotle – f) Animals were classified into those with red blood and those without red blood

Question 3.
Which of the following does not belong to the group? What is the common feature of the others?
A. Housefly, Lizard, Butterfly, Grasshopper
B. Cat, Dog, Tiger, Snake
C. Arecanut tree, Coconut tree, Jack tree, Palm tree
Answer:
A. Housefly, Lizard, Butterfly, Grasshopper
Does not belong: Lizard Common feature of others: They are all insects (belonging to Class Insecta,
Phylum Arthropoda). Lizards are reptiles (Class Reptilia, Phylum Chordata).

B. Cat, Dog, Tiger, Snake Does not belong: Snake Common feature of others: They are all mammals (belonging to Class Mammalia). Snakes are reptiles (Class Reptilia).

C. Arecanut tree, Coconut tree, Jack tree, Palm tree
Does not belong: Jack tree
Common feature of others: They are all types of palm trees (belonging to the Family Arecaceae, Class Liliopsida – Monocots). Jack tree belongs to a different family (Moraceae) and is a dicot.

Basic Science Class 8 Chapter 16 Question Answer Kerala Syllabus

Textbook Page No : 255

Question 1.
What is the main idea conveyed by the poster?
Answer:
The main idea conveyed by the poster is the vastness of biodiversity on Earth, by showing the large and varied number of identified species in major groups of living organisms (Animals, Plants, Fungus, Protista, and Bacteria/Archaea).

Question 2.
Can you suggest a suitable title for the poster?
Answer:
A suitable title for the poster could be:

• The World of Life: A Glimpse of Biodiversity
• Biodiversity on Earth: Identified Species Count
• Tree of Life: Species Numbers

Question 3.
How is it possible to identify and study so many living organisms?
Answer:
It is possible to identify and study so many living organisms through the branch of science called Taxonomy.

Taxonomy deals with:

• Classifying organisms by comparing their characteristics, and identifying similarities and differences.
• Giving them scientific names (Nomenclature).
• This systematic approach, using different levels of classification (Taxa), allows scientists to organize and understand the relationships between the vast number of organisms (biodiversity).

Textbook Page No : 257 & 258

Question 4.
What are the classification levels between species and phylum?
Answer:
Referring to the levels of classification, the levels between species and phylum are:

• Genus
• Family
• Order
• Class

Question 5.
Complete Table 16.1 for the classification levels of the Tiger:

Answer:

Levels of classification	Group and characteristics	Organisms (Example/ Group)
Kingdom:	Animalia (Animals) – Multicellular, eukaryotic, heterotrophic organisms.	Tiger, Cat, Human, Fish etc.
Phylum:	Chordata (Vertebrates) – Presence of vertebrae and vertebral column.	Tiger, Cat, Human, Fish
Class:	Mammalia (Mammals) – Warmblooded, body covered with hair, nourish young ones with milk.	Tiger, Cat, Human
Order:	Carnivora (Carnivores) – Sharp teeth and claws adapted for hunting and eating meat.	Tiger, Cat
Family:	Felidae – Retractable claws, excellent night vision.	Tiger, Cat
Genus:	Panthera (Big cats) – Ability to roar, large and powerful body structure.	Tiger, Lion, Leopard
Species:	Panthera tigris (Tiger) – Orange fur with black stripes and strong large body.	Tiger

Textbook Page No : 260

Question 6.
Can we include Bacteria, Paramecium, Mushroom, and Yeast in the Plant or Animal kingdoms? Why?
Answer:
No, we cannot include them in the Plant or Animal kingdoms.
Reason: The Two-Kingdom classification (Plantae and Animalia) was insufficient because it did not account for characteristics of these organisms.

• Bacteria are prokaryotes (no distinct nucleus).
• Paramecium is a unicellular eukaryote.
• Fungi (Mushroom/Yeast) are saprophytes and do not have chlorophyll to perform photosynthesis like plants.

Textbook Page No : 262

Question 7.
Complete Table 16.3: Five Kingdom Classification

Answer:

Kingdom	Characteristics	Examples
Monera	Prokaryotes, do not have a distinct nucleus.	Bacteria
Protista	Mostly unicellular eukaryotes. Can be autotrophs or heterotrophs. Move via flagella, cilia, or pseudopodia.	Amoeba, Paramecium, Euglena
Fungi	Eukaryotic saprophytes. Do not have chlorophyll.	Mould, Yeast, Mushroom Plantae
Plantae	Multicellular eukaryotes that produce their own food (photosynthesis).	Plants (Coconut tree, etc.)
Animalia	Multicellular eukaryotes and heterotrophs. Have locomotory organs.	Sponges, Humans, Tiger

Textbook Page No : 264

Question 8.
Complete Table 16.4 for Scientific Names:

Answer:

Organism	Scientific Name
Tiger	Panthera tigris
Coconut tree	Cocos nucifera
Dog	Canis familiaris (The text provides no specific information, but this is the correct scientific name)

Textbook Page No : 266
Indicators

Question 9.
Limitations of classification based only on external features
Answer:
Classification based solely on external appearance is often inaccurate because it can separate organisms that are actually closely related biologically.

• The text uses the example of Wolffia (a tiny floating plant) and Anthurium (a larger flowering plant). Despite looking very different externally, they belong to the same family (Araceae) because they are genetically related and share a common ancestor.
• Conversely, Salvinia and Wolffia might look somewhat similar (both small aquatic plants), but Salvinia is a non-flowering fern (Family Salviniaceae) while Wolffia is a flowering plant.

Therefore, relying only on external structure can lead to errors in grouping.

Question 10.
Changes in the criteria of classification
Answer:
The criteria for classification have evolved from simple observations to complex scientific analysis.

• Past Criteria: In early days, classification was based merely on external structure and utility (usefulness).
• Modern Criteria: Today, classification considers evolutionary (phylogenetic) relationships and genetic characteristics.
• Result: This shift led to the splitting of Kingdom Monera into Archaebacteria and Eubacteria based on molecular studies.

Textbook Page No : 267

Question 11.
Do all humans belong to the same species?
Answer:
Yes.
Although humans living in different parts of the world show variations in external appearance (due to local geography and environmental factors), there are no significant genetic or other fundamental differences among them. All humans around the world share a common ancestor and can interbreed to produce fertile offspring. That is why all humans are classified under the same species, sapiens (within the genus Homo).

Class 8 Basic Science Chapter 16 Question Answer Extended Activities

Question 1.
Prepare a magazine including pictures and contributions of scientists related to the history of classification.

Question 2.
List the plants found in the school surroundings and biodiversity parks, find their scientific names, and display them.

Tree of Life Class 8 Notes

Class 8 Basic Science Tree of Life Notes Kerala Syllabus

Introduction: Biodiversity
The Earth is home to a vast number of diverse living organisms, including plants, animals, fungi, bacteria, and protists. How is it possible to identify and study so many different living things?. Attempts to classify and study them began a long time ago.

Early Attempts at Classification

• Aristotle (അരിസ്റ്റോട്ടിൽ): Classified living beings based on whether they had red blood or not.
• Theophrastus (തിയോഫാസ്റ്റസ്): Classified plants into trees, shrubs, and herbs.

• Carl Linnaeus (കാൾലിനേയസ്): Introduced the different levels of classification and provided a scientific foundation for it. He is considered the Father of Taxonomy.

• John Ray (ജോൺ റേ): Initiated the scientific method of classification and was the first to use the term ‘species’.

• Ernst Haeckel (ഏണസ്റ്റ് ഹെക്കൽ): Classified living organisms into three kingdoms: Animalia, Plantae, and Protista.

Taxonomy (വർഗ്ഗീകരണശാസ്ത്രം)
The branch of science that deals with classifying organisms by comparing characteristics, identifying similarities/differences, and giving scientific names.
Importance: Helps understand biodiversity and relationships between organisms.

Father of Taxonomy: Carl Linnaeus.
ജീവികളെ തിരിച്ചറിയുകയും, സാമ്യതകളുടെയും വ്യത്യാസങ്ങളുടെയും അടിസ്ഥാനത്തിൽ തരംതി രിക്കുകയും, ശാസ്ത്രീയ നാമം നൽകുകയും ചെ യ്യുന്ന ശാസ്ത്രശാഖയാണ് ടാക്സോണമി. ഇതി ലൂടെ ജീവവൈവിധ്യത്തെക്കുറിച്ചും ജീവികൾ ത മ്മിലുള്ള ബന്ധങ്ങളെക്കുറിച്ചും മനസ്സിലാക്കാം.

Levels of Classification (വർഗ്ഗീകരണ തലങ്ങൾ)
Linnaeus proposed a hierarchical system for classifying organisms, starting from broad categories and becoming more specific.

The Main Steps in Classification:

1. Identification (തിരിച്ചറിയൽ)
2. Classification (വർഗ്ഗീകരണം)
3. Naming (നാമകരണം)
   The Hierarchy (Illustration 16.1):
   The levels, from broadest to most specific, are:

Species

• A species is a group of organisms that can naturally reproduce to form fertile offspring (പ്രത്യുത്പാദന ശേഷിയുള്ള തലമു).
• This is the most basic level of classification.
• Examples: Human beings, cats, dogs, and cashew trees are examples of different species. All humans belong to the same species, sapiens.

Classification Systems (വർഗ്ഗീകരണ രീതികൾ)

• The classification levels developed by Carl Linnaeus are still used today. These levels (Kingdom, Phylum, Class, etc.) are called Taxa. Plants can also be classified using these levels, from species to kingdom.
• Two-Kingdom Classification System (ദ്വികിങ്ഡം വർഗീകരണം)
  • Proposed by Carl Linnaeus.
  • Divided all living organisms into two kingdoms:
    1. Kingdom Animalia (Animals)
    2. Kingdom Plantae (Plants).
• Classification level of the coconut tree

Kingdom	Plantae (Plants) – Multicellular, eukaryotic, autotrophic organisms.
Division	Magnoliophyta (Flowering plants) – Plants with seeds enclosed inside fruits.
Class	Liliopsida (Monocotyledons) – Plants with parallel leaf venation and fibrous roots.
Order	Arecales – Plants with long and hard stems.
Family	Arecaceae – Plants with large compound leaves and unbranched stems.
Genus	Cocos – Produces large, single-seeded fruits.
Species	Cocos nucifera (Coconut) – Produces fruits with a hard shell, fibrous husk, with a liquid and solid endosperm, inside.

Limitations of the Two-Kingdom System

• Many organisms (like Bacteria, Paramecium, Mushroom, Yeast – see Fig 16.8) do not fit neatly into either the Plant or Animal kingdom.
• Bacteria: Unicellular, Prokaryote. (Plants/Animal are Eukaryotes).
  • Paramecium: Unicellular, Eukaryote, Heterotroph, Mobile. (Plants are autotrophs; some animals are multicellular).

• • Mushroom/Yeast: Eukaryote, Heterotroph (saprophyte), No mobility. (Plants are autotrophs; Animals are usually mobile).

• This showed the need for a more comprehensive system.

Five-Kingdom Classification System (പഞ്ചകിങ്ഡം വർഗീകരണം)

• Proposed by Robert H. Whittaker to overcome the limitations of the two-kingdom system.
• Classified organisms into five kingdoms:

Kingdom	Cell Type	Multicellularity	Mode of Nutrition	Key Characteristics & Examples
Monera	Prokaryotes	Unicellular	Autotrophic or Heteroirophic	Do not have a distinct nucleus. Simplest and most ancient organisms. Eg: Bacteria.
Protista	Eukaryotes	Unicellular	Autotrophic or Heterotrophic	Mostly aquatic. Have locomotory structures like flagella, cilia, and pseudopodia. Eg: Amoeba, Paramecium, Euglena.
Fungi	Eukaryotes	Mostly Multicellular	Heterotrophs (Saprophytes)	Do not have chlorophyll. Absorb nutrients from dead and decaying matter. Cell wall made of chitin. Eg: Mould, Yeast, Mushroom.
Plantae	Eukaryotes	Multicellular	Autotrophs (Photosynthesis)	Primary producers. Have roots, stems, and leaves.
Animalia	Eukaryotes	Multicellular	Heterotrophs	Have locomotory organs and definite receptors. Eg: Sponges to humans.

• Advantage of Five-Kingdom Classification: It provides a more accurate and detailed way to group organisms, especially microorganisms like bacteria, protists, and fungi, which didn’t fit well into the older two-kingdom system.

Closer Look at Some Kingdoms

• Kingdom Monera
  • Characteristics: The simplest and most ancient organisms. They are all unicellular and prokaryotic (lack a distinct nucleus).
  • Main Group: Bacteria.
  • Occurrence: Found everywhere – soil, water, air, food, inside our bodies.
  • Role: Important in nutrient cycles (like nitrogen fixation). Most are useful, but some cause diseases.
• Kingdom Protista

• • Characteristics: Unicellular eukaryotes. Most live in aquatic habitats.
  • Examples: Paramecium, Amoeba, Euglena.
  • Disease-causing Protists: Plasmodium (causes malaria), Entamoeba histolytica (causes amoebic dysentery).
• Kingdom Fungi
  • Characteristics: Eukaryotes. Mostly multicellular (except for unicellular yeast). Have a cell wall made of chitin. Do not have chlorophyll and cannot perform photosynthesis. They are saprophytes, absorbing nutrients from dead and decaying matter.
  • Examples: Mould on bread, mushrooms, yeast.

• • Uses: Edible mushrooms, yeast (used in baking wine alcohol production) candidiasis and ringworm.

The section discusses:

• The variety of local names for a plant (like Papaya).
• The difficulty in identifying and studying the same organism when it is known by different names.
• The solution: giving names that are universally accepted beyond language barriers.
• This solution is Binomial Nomenclature, a scientific method developed by Carl Linnaeus, where the name consists of the genus and species name.
• The names are often in Latin or transformed to the Latin style to ensure they are the same everywhere in the world.
• For example, the scientific name of a human is Homo sapiens.

Binomial Nomenclature (ദ്വിനാമ പദ്ധതി)

• Developed by: Carl Linnaeus.
• A universally accepted scientific method of naming organisms using two parts: the Genus name (first, capitalized) and the Species name (second, lowercase).
• Format: Written in italics or underlined.
• Importance: Provides a unique, universal name for each organism, avoiding confusion from common names.
• Example: Homo sapiens (Human), Panthera tigris (Tiger).

ജീവികൾക്ക് ലോകമെമ്പാടും അംഗീകരിക്കപ്പെട്ട ഒരു ശാസ്ത്രീയനാമം നൽകുന്ന രീതിയാണ് ദ്വിനാ മ പദ്ധതി. ഇതിൽ ആദ്യപദം ജീനസിനെയും (Genus) രണ്ടാം പദം സ്പീഷീസിനെയും (Species) കുറിക്കുന്നു. ഉദാ: Homo sapiens (മനുഷ്യൻ).

New Paths in Classification (വർഗ്ഗീകരണത്തിലെ പുതിയ രീതികൾ)
Classification methods are not static; they are constantly being revised based on new discoveries and understanding.

Limitations of Early Methods:

• Early classification was often based only on external features (morphology) and utility.
• Problem: Organisms that look similar externally might not be closely related, and organisms that look different might actually be closely related.
• Example (Fig 16.16): Wolffia (a tiny flowering plant) and Salvinia (a non-flowering fern-like plant) look some what similar externally but belong to completely different families based on evolutionary and genetic characteristics. Wolffia is in the family Araceae (like Anthurium), while Salvinia is in Salviniaceae (like Azolla).

Modern Classification Methodology:
Today, classification considers not only physical characteristics but also:

• Evolutionary relationships (Phylogenetics)
• Genetic characteristics

Six-Kingdom Classification System (ആറ് കിങ്ഡം വർഗ്ഗീകരണം)
As scientific understanding, particularly in molecular studies, progressed, the Five-Kingdom system was further refined.

• Proposer: The scientist Carl Woese introduced the Six-Kingdom classification system.
• Change: Based on modern scientific observations, the Kingdom Monera (which contained all prokaryotes) was divided into two distinct kingdoms.
• The Split: Monera was split into:
  • Kingdom Archaebacteria ( കീരിയ ആർക്കിബാ)
  • Kingdom Eubacteria (യുബാക്ടീരിയ).

ശാസ്ത്രീയ നിരീക്ഷണങ്ങളുടെ അടിസ്ഥാനത്തിൽ, കാൾ ഷൂസ് എന്ന ശാസ്ത്രജ്ഞൻ വർഗ്ഗീകരണ രീതി പരിഷ്കരിച്ചു. അദ്ദേഹം മൊണീറ എന്ന കി ങ്ഡത്തെ ആർക്കിബാക്ടീരിയ, യൂബാക്ടീരിയ എ ന്നിങ്ങനെ രണ്ടായി വിഭജിച്ചു. അങ്ങനെ മൊത്തം ആറ് കിങ്ഡങ്ങൾ നിലവിൽ വന്നു.

Do all Humans Belong to the Same Species?
Despite differences in external appearance among humans living in different parts of the Earth, which may be due to the influence of local geography and environmental factors, there is no significant genetic or other fundamental difference among them.

• All humans around the world share a common ancestor.
• Therefore, all humans are classified under the same species: sapiens.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 15 Chemistry of Matter Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 15 Chemistry of Matter Question Answer Notes

Class 8 Basic Science Chapter 15 Notes Kerala Syllabus Chemistry of Matter Question Answer

Chemistry of Matter Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Which of the following is made of a synthetic material?
a. Iron nail
b. Aluminium vessel
c. Glass test tube
d. Gold ornament
Answer:
W c. Glass test tube.
Reason: Glass is a synthetic material made by reacting silica (sand) with metal salts at high temperatures. Iron, Aluminium, and Gold are metals derived from natural sources.

Question 2.
Which of the following is not a polymer?
a. Bakelite
b. PVC
c. Rubber
d. Copper
Answer:
d. Copper.
Reason: Bakelite, PVC, and Rubber (natural or synthetic) are polymers, which are large molecules formed from repeating smaller units called monomers. Copper is a metallic element.

Question 3.
What is the difference between thermoplastics and thermosets?
Answer:
The main difference lies in their response to heat after moulding:
Thermoplastics (like polythene) can be reheated, melted, and reshaped into new products multiple times.
Thermosetting plastics (or thermosets, like Bakelite) cannot be reheated and melted to make new reshaped products once they are set.

Question 4.
Write one reason why synthetic rubber is used in the manufacture of tyres.
Answer:
Synthetic rubber shows less wear and tear compared to natural rubber, making it more durable for use in tyres.

Question 5.
What is the advantage of blending natural fibres along with synthetic fibres?
Answer:
Blending is done to overcome the limitations of both types of fibres. For example, blending cotton (natural) with polyester (synthetic) can create a fabric that has the comfort and breathability of cotton but the durability, wrinkle resistance, and quick-drying properties of polyester.

Question 6.
“Material chemistry provides us with both advantages and disadvantages” Do you agree with this statement? Why?
Answer:
B Yes, I agree with the statement. Advantages: Material chemistry has transformed various natural substances into countless useful products that have improved our quality of life, such as glass for various applications, durable plastics, elastic rubbers, versatile fibres, medicines, soaps, paints, etc.. It plays a crucial role in human progress by creating new materials with suitable properties.

Disadvantages: The production and uncontrolled use of some synthetic materials, particularly plastics, lead to significant environmental problems like plastic pollution. This pollution affects soil, water, and air, harming plants, animals, and ecosystems. Disposal of these materials is often difficult as many are not easily biodegradable.

Basic Science Class 8 Chapter 15 Question Answer Kerala Syllabus

Textbook Page No : 245 & 246

Question 1.
Why does the panchayat give importance to the conservation of water resources? (Discussion)?

Answer:

Items made from natural materials	Items made from synthetic materials
Door – Made of wood	Jar – Made of glass
Chair (wicker) – Made of cane/ rattan	Chair (plastic) – Made of plastic
Rope (jute/coir) – Made of natural fibers	Tyre – Made of synthetic rubber/ plastic
Hammer handle – Made of wood	Bucket – Made of plastic
Vessels (steel) – Made from processed metals	Balloons – Made of rubber/latex (can be natural or synthetic)
Tiffin carrier (steel) – Made from processed metals	Rope (nylon) – Made of synthetic fiber

Question 2.
Try writing down the items made of glass:

Answer:
Mirror

1. Glass jar
2. Windows/Panes
3. Car windshields
4. Beakers and laboratory equipment
5. Bottles
6. Light bulbs
7. Spectacle lenses
8. Lenses
9. Prisms

Textbook Page No : 247

Question 3.
Are the glasses used to make the objects shown in the picture of the same type?
Answer:
No, they are not of the same type. Different types of glass are manufactured by modifying the chemical composition to achieve specific properties for various applications (e.g., thermal resistance for ovenware, or specific refractive index for lenses).

Question 4.
Why can water be used for so many purposes?
Answer:
Water can be used for so many purposes primarily because of its special property as a universal solvent. Water can dissolve a wide variety of substances , and the nature of the water changes depending on what is dissolved in it, allowing it to be used to make different types of solutions. This solubility is one of the main reasons for its varied uses.

Question 5.
Haven’t you seen the shattered glasses of vehicles met with accidents? What is special about them?
Answer:
The glasses used in most vehicle wind-screens (front windshields) are usually Laminated glass, and sometimes side/ rear windows are Tempered glass.

• Laminated glass is special because it is made of two layers of glass bonded by a plastic inner layer (PVB). When it shatters, the fragments stick to the plastic, preventing sharp pieces from flying and causing injury.
• Tempered glass shatters into small, blunt, granular fragments instead of large, sharp shards, which reduces the risk of injury.

Question 6.
Do you know the name of glass used in the display of mobile phones?
Answer:
display of most modern mobile phones is covered with a type of chemically strengthened Aluminosilicate glass (e.g., Gorilla Glass or Dragontrail Glass). It is chosen for its superior scratch resistance and toughness.

Question 7.
Table Completion (Table 15.2)

Answer:

Types of Glasses	Uses	Major Components
Soda-lime glass/Soft glass	To make mirrors, window glass, bottles, etc.	Silica, Sodium oxide, Calcium oxide
Borosilicate Glass	To make laboratory equipment, cookwares, etc.	Silica, Boric acid (or Boric oxide), Sodium oxide, Aluminium oxide
Flint Glass /Optical Glass	Used in the manufacture of lenses, prisms, etc.	Silica, Lead oxide, Potassium oxide
Quartz glass	Apparatus used in chemical laboratories, electric bulbs.	Silica

Question 8.
Which is the component present in ail types of glass?
Answer:
Silica (SiO₂). It is the primary glass-forming material in almost all commercial types of glass.

Question 9.
Find out the other components present in each type of glass.
Answer:
The main components besides Silica are:
Soda-lime glass: Sodium oxide (Na₂O) and Calcium oxide (CaO).
Borosilicate glass: Boric acid/Boric oxide (B₂O₃), Sodium oxide (Na₂O), and Aluminium oxide (Al₂O₃).
Flint Glass/Optical Glass: Lead oxide (PbO) and Potassium oxide (K₂O). (In modern, lead-free flint glasses, lead oxide is sometimes replaced by oxides of Titanium or Zirconium.)

Textbook Page No : 248 & 249

Question 10.
Try writing down the common properties of glass:
Answer:
Based on the nature and uses of glass, the common properties are:

1. Transparency
2. Amorphous (non-crystalline solid)
3. Brittle (breaks suddenly)
4. Chemically resistant (to most common chemicals)
5. Poor conductor of heat and electricity

Question 11.
Haven’t you seen glasses of different colours? How do they get their colour?
Answer:
Glasses get a variety of colors when different chemicals (usually metal oxides) are added during the manufacturing process. These chemicals mix into the molten glass and impart a specific hue.

Question 12.
Why does the molecular mass increase when monomers participate in polymerisation? Can you observe and explain that from the above picture?

Answer:
The molecular mass increases significantly because monomers (small molecules) chemically combine under high pressure and temperature to form a single, very large molecule called a polymer.
Explanation from the picture (Fig 15.6): The diagram illustrates that the Dimer is formed by combining two Monomers, and the Polymer is formed by joining many Monomers in a long chain. The final polymer molecule is simply the accumulated mass of all the individual monomers, resulting in a much higher molecular mass compared to the initial molecules.

Monomer and Polymer

Question 13.
Plastic tables, chairs, etc. can be manufactured easier than wooden ones. Why?
Answer:
Plastic items are easier to manufacture because plastics are polymers that are generally thermoplastics. This means they can be easily melted and molded into complex shapes and designs using industrial processes (like injection molding) in a continuous and rapid manner. Manufacturing wooden objects requires more complex processes like cutting, carving, and joining.

Textbook Page No : 250 & 251

Question 14.
Plastics are widely used due to their unique properties compared to natural materials:
Answer:

1. Can be reshaped (miss)
2. Lightweight
3. Durable
4. Often resistant to chemicals
5. Can be electrical insulators
6. Can be moulded into various shapes easily

Question 15.
Are most of the objects we use daily, natural or synthetic? Discuss.
Answer:
Most of the objects we use daily are made of synthetic materials (polymers like plastics) or contain major synthetic components. While natural materials (like wood, metal, cotton) are still essential, synthetic polymers are favored for massproduced items because they are:

• Less expensive to produce.
• Lightweight and durable.
• Easily molded into various shapes (versatility).
• Resistant to moisture and decay.

Question 16.
How can we identify different types of plastics? What do they indicate?
Answer:
We identify different types of plastics using the Recycling Symbols. These are symbols consisting of a triangle made of chasing arrows, with a number (1 – 7) inside and an abbreviation below

These symbols indicate:

1. The specific type of polymer the item is made from (e.g., PET, PVC, HDPE).
2. The recyclability of the material and how it should be sorted for recycling.

Textbook Page No : 252 & 253

Question 17.
Analysis and Debate: Plastic – Friend or Foe?
Answer:
The discussion revolves around the necessary regulation of plastics in addition to the 4R method (Refuse, Reduce, Reuse, Recycle).

Aspect	Argument (Plastic)	Justification
Friend (Advantages)	Plastic is essential and unavoidable.	Used for diverse benefits. Essential for modern life (e.g., packaging, cables, pipes, bottles.
Foe (Disadvantages)	Uncontrolled use causes environmental damage.	Accumulates and causes water and soil pollution. Alters the natural chemical composition of soil, air, and water, affecting plant and organism growth.
Regulation	Regulation is necessary.	The 4R method alone may not completely avoid pollution; production and distribution of single-use disposable products must also be regulated. The newspaper report highlights strict government actions, fines, and bans as part of this regulation.

Question 18.
Write one reason why synthetic rubber is used in the manufacture of tyres.
Answer:
Synthetic rubbers are used in the manufacture of tyres because they show less wear and tear compared to natural rubber, making them more durable.

Question 19.
Try pulling and stretching a jute rope and a rubber band with force. What happens? Why?
Answer:

Material	What Happens	Why?
Jute Rope	It will stretch very little and may snap or break if enough force is applied.	Jute is a natural fibre, and fibres are polymers that are designed to be strong with low elasticity.
Rubber Band	It stretches significantly with less force and recoils when released.	Rubber is a polymer with an inherent elastic nature.

Question 20.
Comparison of Natural and Synthetic Fibres (Completing Table 15.3)

Answer:

Characteristics	Natural Fibres	Synthetic
Air circulation	More	Fibres
Water absorption	More	Less
Durability	Lower	Less
Weight	Higher	Higher

Question 21.
What is the advantage of blending natural fibres along with synthetic fibres?
Answer:
The advantage is to overcome the limitations of both types. Blending combines the best properties of both, such as the comfort and good water absorption of natural fibres with the durability, strength, and wrinkle resistance of synthetic fibres.

Question 22.
Write down the uses of fibres.
Answer:
Apart from clothing, fibres are used for:

• Making ropes, mats, and nets.
• Making fishing nets (e.g., Nylon fibres).
• Used to prevent soil erosion and to make geotextiles for agricultural use.

Question 23.
Complete the table based on polymer characteristics (Completing Table 15.8).

Answer:

Characteristics	Polymer
Suitable for making strong threads	Nylon (or Polyester)
Polymer that can be moulded into various shapes	Plastic
Polymer with elastic nature	Rubber (Natural or Synthetic)

Textbook Page No : 254

Question 24.
List the other materials around us that are made with the help of chemistry.
Answer:

1. Dyes
2. Perfumes
3. Soaps
4. Medicines
5. Fertilizers
6. Pesticides
7. Cosmetics

Class 8 Basic Science Chapter 15 Question Answer Extended Activities

Question 1.
Organize an exhibition on the theme “The Discovery of Glass and the Growth of Science,” including descriptions and pictures of the history of glass making and different types of glasses.

Question 2.
Prepare a seminar paper on the topic “Microplastic Pollution”

Chemistry of Matter Class 8 Notes

Class 8 Basic Science Chemistry of Matter Notes Kerala Syllabus

Natural vs. Synthetic Materials
We use diverse objects made from both natural substances and synthetic materials. Material Chemistry is the branch of science that helps transform various substances into useful products for humans.

• Natural Materials: Obtained directly from nature (e.g., wood, cotton, jute).
• Synthetic Materials: Man-made materials, often produced through chemical processes (e.g., glass, plastic).

Glass
Glass is a synthetic material and an amorphous (non-crystalline) transparent substance.

Manufacturing and Composition

• Glass is formed when silicon dioxide in sand undergoes a chemical reaction with metal salts at high temperatures.
• The primary component present in all types of glass is Silica (SiO₂).
• The accidental discovery of glass is attributed to Phoenician mariners who used blocks of washing soda (Sodium carbonate) to build a hearth on a sandy bank.

□ Properties and Colouring of Glass
Common Properties of Glass:

• Transparency (സുതാര്യത)
• Brittleness (എളുപ്പത്തിൽ പൊട്ടുന്നത്)
• Hardness
• Resistance to heat (varies by type)
• Usually an electrical insulator

□ Colouring Glass:
Glasses get different colours when specific chemicals are added during the manufacturing process.

□ Chemicals and Glass Colours

Chemicals Added	Colour of the Glass Obtained
Cadmium sulphide	Yellow
Gold chloride	Ruby red
Chromium oxide	Green
Cobalt oxide	Blue

□ Types:
Different types of glass are made by varying the components added to silica.

• Soda lime glass: Bottles, window glass.
• Borosilicate glass: Lab equipment, cookware.
• Flint glass: Lenses, prisms.
• Common Component: Silica (SiO₂) is present in all types.

ഗ്ലാസ് ഒരു കൃത്രിമ പദാർത്ഥമാണ്. മണലിലെ സിലിക്കയും (SiO₂) ലോഹ ലവണങ്ങളും (metal salts) ഉയർന്ന താപനിലയിൽ പ്രവർത്തിച്ചാണ് ഗ്ലാസ് ഉണ്ടാക്കുന്നത്. വിവിധ രാസവസ്തുക്കൾ ചേർത്ത് ഗ്ലാസിന് നിറം നൽകാം.

Polymers
Many synthetic materials like plastics, rubber, and synthetic fibres belong to a group called polymers.

Polymerisation (പോളിമറൈസേഷൻ):
Polymerisation is the process in which many small molecules combine under high pressure and temperature to form large molecules.

Monomers (മോണോമറുകൾ): The small molecules used in polymerisation are called monomers.
Polymers (പോളിമറുകൾ): The large molecules formed by the combination of a large number of monomers are called polymers.

Key Points:

• The study of polymers is known as polymer chemistry.
• Hermann Staudinger is known as the Father of Polymer Chemistry.
• Bakelite is the first synthetic polymer.
• Polymers have much higher molecular mass than ordinary molecules, leading to different properties.

അനേകം ചെറിയ തന്മാത്രകൾ (മോണോമറുകൾ) ഉയർന്ന മർദ്ദത്തിലും താപനിലയിലും സംയോജി ച്ച് വലിയ തന്മാത്രകൾ (പോളിമറുകൾ) ഉണ്ടാകു ന്ന പ്രിയയാണ് പോളിമറൈസേഷൻ. പ്ലാസ്റ്റിക്, റബ്ബർ, നാരുകൾ എന്നിവയെല്ലാം പോളിമറുകൾ ക്ക് ഉദാഹരണമാണ്.

□ Classification of Polymers
Polymers can be classified in different ways:
1. Based on Physical Properties: They can be grouped into plastics, rubber, and fibres.

□ Based on Origin:
Natural Polymers: Found in nature.
Synthetic Polymers: Man-made polymers.

Natural Polymers	Synthetic Polymers
Cellulose	Polythene
Starch	Nylon
Natural rubber	Bakelite
	PVC, Synthetic rubbers

□ Common Synthetic Polymers and Their Uses

Polymer	Characteristics	Uses
Polyethylene (Polythene)	Inert nature (രാസപ്രവർത്ത നത്തിൽ ഏർപ്പെടാത്ത സ്വഭാവം)	Food containers, packaging
Polytetrafluoroethylene (PTFE / Teflon)	Heat resistance (താപം പ്രതിരോധിക്കാനുള്ള കഴിവ്)	Cookwares used at high temperatures (Non-stick)
Polyvinyl chloride (PVC)	Electrical resistance (വൈദ്യുതി പ്രതിരോധിക്കാനുള്ള കഴിവ്)	Cables, Pipes
Polyethylene terephthalate (PET)	Prevents gas permeation (വാതകങ്ങളെ കടത്തിവിടില്ല)	Used in bottle manufacturing

Plastics
Plastics are highly demanded due to their unique properties, such as being

• Can be reshaped (രൂപമാറ്റം വരുത്താം)
• Lightweight
• Durable
• Often resistant to chemicals
• Can be electrical insulators
• Can be moulded into various shapes easily

□ Classification of Plastics
Plastics can be further classified based on their behaviour when heated:
1. Thermoplastics:
These plastics can be reheated, melted, and reshaped into new products multiple times. They soften on heating and harden on cooling.
Example: The plastic carry bags we use (Polythene), PVC pipes.

2. Thermosetting Plastics:
These plastics cannot be reheated and melted to reshape them once they have been set. They undergo a permanent chemical change during moulding.
Example: Items like the handle of a pressure cooker (e.g., Bakelite).
ചൂടാക്കുമ്പോൾ മൃദുവാകുകയും തണുപ്പിക്കു മ്പോൾ ഉറയ്ക്കുകയും ചെയ്യുന്ന പ്ലാസ്റ്റിക്കുകളാണ് തെർമോപ്ലാസ്റ്റിക്കുകൾ. ഇവയെ വീണ്ടും ചൂടാക്കി രൂപമാറ്റം വരുത്താൻ കഴിയും. എന്നാൽ, നിർമ്മാ ണ വേളയിൽ ചൂടാക്കുമ്പോൾ ഉറയ്ക്കുകയും, പി ന്നീട് ചൂടാക്കിയാൽ മൃദുവാകാത്തതുമായ പ്ലാസ്റ്റി ക്കുകളാണ് തെർമോസെറ്റിംഗ് പ്ലാസ്റ്റിക്കുകൾ. ഇ വയെ വീണ്ടും രൂപമാറ്റം വരുത്താൻ സാധ്യമല്ല.

□ Identifying Different Types of Plastics
Different types of plastics have specific properties and recycling potential. They are often identified using Resin Identification Codes (the number inside the chasing arrows symbol).

Plastic Pollution ((പ്ലാസ്റ്റിക് മലിനീകരണം)
While plastics have many benefits, their uncontrolled use leads to significant environmental problems.

• Problem: Plastics accumulate in the environment, causing water and soil pollution. They alter the natural composition of soil, air, and water, affecting the growth of plants and soil organisms.
• Solution (The 4R Approach): To reduce plastic pollution, the 4R approach is recommended:
  • Refuse (ഒഴിവാക്കുക): Avoid giving or accepting plastic products whenever possible.
  • Reduce (ഉപയോഗം കുറയ്ക്കുക): Minimise the use of plastic products.
  • Reuse (പുനരുപയോഗിക്കുക): Reuse plastic products multiple times.
  • Recycle (പുനഃചംക്രമണം ചെയ്യുക): Convert plastic products into new items through physical and chemical processes.
• Regulation: Governments are also taking action by banning certain single-use plastics and imposing fines for littering.

Rubbers (റബ്ബറുകൾ)
Rubbers are polymers known for their elastic nature.

• Natural Rubber:
  • An elastic natural polymer.
  • Obtained from the latex collected from the rubber tree.
• Synthetic Rubber:
  • Produced to meet increased demand and overcome limitations of natural rubber.
  • Shows less wear and tear compared to natural rubber.
  • Use: Widely used in the manufacture of tyres.

Fibres (നാരുകൾ)

• Fibres are polymers that are strong and long.
• For a polymer to be considered a fibre, its length must be at least a hundred times its diameter.
• Uses: Apart from clothing, fibres are used to make ropes, mats, nets, geotextiles, etc..
• Synthetic Fibres:
  • Developed to overcome the limited availability and quality issues of natural fibres.
  • Nylon is the first synthetic fibre made by humans.
• Blending Fibres: To overcome the limitations of both types, natural fibres are often blended with synthetic fibres.

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 15 Chemistry of Matter Important Questions ensure conceptual clarity.

Chemistry of Matter Extra Questions and Answers Class 8 Basic Science Chapter 15 Kerala Syllabus

Chemistry of Matter Class 8 Important Questions

Question 1.
Match the polymer type in Column A with its characteristic in Column B.

Column A	Column B
(i) Thermoplastic	(a) Cannot be remelted and reshaped.
(ii) Thermosetting Plastic	(b) Can be reheated and reshaped multiple times.
(iii) Fibre	(c) Polymer with elastic nature.
(iv) Rubber	(d) Polymer suitable for making strong threads.

Answer:
(i) – b, (ii) – a, (iii) – d, (iv) – c

Column A	Column B
(i) Thermoplastic	(b) Can be reheated and reshaped multiple times.
(ii) Thermosetting Plastic	(a) Cannot be remelted and reshaped.
(iii) Fibre	(d) Polymer suitable for making strong threads.
(iv) Rubber	(c) Polymer with elastic nature.

Question 2.
Match the type of glass in Column A with its major use in Column B.

Column A	Column B
(i) Soda lime glass	(a) Lenses, prisms
(ii) Borosilicate glass	(b) Window glass, bottles
(iii) Flint glass	(c) Laboratory equipment, cookware

Answer:
(i) – b, (ii) – c, (iii) – a

Column A	Column B
(i) Soda lime glass	(b) Window glass, bottles
(ii) Borosilicate glass	(c) Laboratory equipment, cookware
(iii) Flint glass	(a) Lenses, prisms

Question 3.
Match the chemical added to glass in Column A with the colour obtained in Column B.

Column A	Column B
(i) Cobalt oxide	(a) Yellow
(ii) Chromium oxide	(b) Ruby red
(iii) Cadmium sulphide	(c) Blue
(iv) Gold chloride	(d) Green

Answer:
(i) – c, (ii) – d, (iii) – a, (iv) – b

Column A	Column B
(i) Cobalt oxide	(c) Blue
(ii) Chromium oxide	(d) Green
(iii) Cadmium sulphide	(a) Yellow
(iv) Gold chloride	(b) Ruby red

Question 4.
Statement (i): Thermoplastics can be reheated and reshaped.
Statement (ii): Thermosetting plastics can also be reheated and reshaped.
(a) Both statements (i) and (ii) are correct.
(b) Statement (i) is correct, but statement (ii) is incorrect.
(c) Statement (ii) is correct, but statemeht (i) is incorrect.
(d) Both statements (i) and (ii) are incorrect.
Answer:
(b) Statement (i) is correct, but statement (ii) is incorrect. (Thermosets cannot be reshaped after setting).

Question 5.
Statement (i): Nylon is the first synthetic fibre made by humans.
Statement (ii): Natural rubber is obtained from the latex of the rubber tree.
(a) Both statements (i) and (ii) are correct.
(b) Statement (i) is correct, but statement (ii) is incorrect.
(c) Statement (ii) is correct, but statement (i) is incorrect.
(d) Both statements (i) and (ii) are incorrect.
Answer:
(a) Both statements (i) and (ii) are correct.

Question 6.
Statement (i): Silica (SiO₂) is the major component present in all common types of glass.
Statement (ii): Glass is considered a natural material.
(a) Both statements (i) and (ii) are correct.
(b) Statement (i) is correct, but statement (ii) is incorrect.
(c) Statement (ii) is correct, but statement (i) is incorrect.
(d) Both statements (i) and (ii) are incorrect.
Answer:
(b) Statement (i) is correct, but statement (ii) is incorrect. (Glass is a synthetic material).

Question 7.
Define Polymerisation, Monomer, and Polymer.
Answer:
Polymerisation: The process in which many small molecules combine under high pressure and temperature to form large molecules.
Monomers: The small molecules used in polymerisation.
Polymers: The large molecules formed by the combination of a large number of monomers.

Question 8.
Explain the ‘4R’ approach recommended to reduce plastic pollution.
Answer:
The 4R approach consists of:
Refuse: Avoid giving or accepting plastic products.
Reduce: Minimise the use of plastic products.
Reuse: Reuse plastic products multiple times.
Recycle: Convert plastic products into new items.

Question 9.
Why are synthetic rubbers often preferred over natural rubber for making tyres?
Answer:
Synthetic rubbers generally show less wear and tear compared to natural rubber, making them more durable and suitable for the demanding conditions tyres face.

Question 10.
How can you identify the type of plastic used in a container using the identification code?
Answer:
Look for the recycling symbol (chasing arrows) on the plastic item. Inside the symbol, there will be a number from 1 to 7. This number corresponds to a specific type of plastic resin (e.g., 1 is PET, 2 is HDPE, 3 is PVC, etc.). You can then refer to a chart (like Table 15.6) to find the abbreviation and name of the plastic.

Question 11.
Describe the observation when a thermoplastic material (like polythene) and a thermosetting material (like Bakelite) are heated strongly after being initially shaped.
Answer:
Thermoplastic: When heated strongly, the thermoplastic material will soften, melt, and can be reshaped.

Thermosetting plastic: When heated strongly, the thermosetting material will not soften or melt. It may char or decompose at very high temperatures but cannot be reshaped.

Question 12.
A student observes the characteristics of natural cotton fibre and synthetic polyester fibre. What differences would they likely note regarding water absorption and durability?
Answer:
Water absorption: The natural cotton fibre would show more water absorption ability compared to the synthetic, polyester fibre.

Durability: The synthetic polyester fibre would likely show more durability (resistance to wear and tear) compared to the natural cotton fibre.

Question 13.
What is the main chemical compound in sand that reacts with metal salts at high temperatures to form glass?
Answer:
Silicon dioxide (SiO₂).

Question 14.
Identify the polymer formed when many ethylene monomers undergo polymerisation.
Answer:
Polyethylene (or Polythene). (The name implies it’s formed from ethylene).

Question 15.
What type of substance is generally formed when silicon dioxide (SiO₂) reacts with metal salts (like sodium carbonate) at high temperature?
Answer:
Glass.

Question 16.
Write the chemical formula for Silica, the main component of glass.
Answer:
SiO₂

Question 17.
Write the full name for the plastic represented by the abbreviation PVC.
Answer:
Polyvinyl chloride.

Question 18.
Observe Figure 15.6, which shows monomers combining to form a polymer. Explain why the molecular mass of a polymer is much higher than that of its monomer.

Answer:
A polymer is formed by chemically combining a large number of individual monomer molecules into a long chain. Therefore, the total mass of the polymer molecule is essentially the sum of the masses of all the monomer units that joined together, making it significantly higher than the mass of a single monomer.

Question 19.
Differentiate between thermoplastic and thermosetting plastic.
Answer:
The plastic that get softened on heating and hardened on cooling is thermoplastics. When heating physical change occurs.

The plastic which remains soft when heated and gets hardened permanently on cooling is thermosetting plastics. Chemical change occurs when heating.

Question 20.
Given some occasions of using plastic. Find the peculiarity of plastic used and fill the table.

Occasion	Peculiarity
As the covering of conductor
To make the handles of cooking vessels
To keep chemicals
To make water tanks
To make house hold materials

Answer:

Occasion	Peculiarity
As the covering of conductor	Plastics are insulators
To make the handles of cooking vessels	Not conducting heat
To keep chemicals	Do not react with chemical
To make water tanks	No rusting. Less weight
To make house hold materials	Easy touse. Less weight

Question 21.
Write 4 occasions which plastic is harmful to daily life.
Answer:

1. Enviromental pollution when it is thrown without any control.
2. When burning air pollution.
3. Hindrance in drainages
4. The water absorption property of soil decreases when plastics are dumped in soil.

Question 22.
What are the uses of plastic in the field of human health?
Answer:

• To produce I V tubes, bottles
• To produce heart valves
• To produce packets

Question 23.
What are the uses of plastic in the field of production of house building.
Answer:
To produce roof materials, doors, plumping and wiring materials.

Question 24.
List the peculiarities of plastic.
Answer:
Can mould in any shape, longlasting, Insulator, do not conduct heats, not reacting with chemicals and water, will burn.

Question 25.
Separate natural and artificial polymer from the list Rubber, wool, p.v.c, Bakelite, nylon, rayon cellulose, silk, polythene, polyester
Answer:

Natural	Artificial
Rubber	p.v.c
Wool	polythene
Cellulose	nylon
Silk	rayon
	Polyester

Question 26.
List the merits of natural and artificial polymer.
Answer:

Merits	Demerits
Comfortable to wear	Less availability
More aeration	wrinkle easily
Absorb water, sweat	high cost
Not easily burns	not durable

Question 27.
If we heat polyethene cover can we convert into earlier stage? Justify.
Answer:
No. Undergoes chemical change because it is thermosetting plastic.

Question 28.
The primary component present in all common types of glass is:
a. Calcium oxide (CaO)
b. Lead oxide (PbO)
c. Silica (SiO₂)
d. Sodium oxide (Na₂O)
Answer:
c. Silica (SiO₂)

Question 29.
The small molecules that combine in a process called polymerisation to form a very large molecule are known as:
a. Isomers
b. Polymers
c. Monomers
d. Dimers
Answer:
c. Monomers

Question 30.
Which of the following is a Thermosetting Plastic?
a. Polythene
b. PVC
c. Bakelite
d. PET
Answer:
c. Bakelite

Question 31.
The plastic recycling code ‘2’ with the abbreviation HDPE is used for:
a Polyvinyl Chloride
b. Low-Density Polyethylene
c. High-Density Polyethylene
d. Polystyrene
Answer:
c. High-Density Polyethylene

Question 32.
Which chemical is typically added to molten glass to achieve a Ruby Red colour?
a. Cobalt oxide
b. Chromium oxide
c. Cadmium sulphide
d. Gold chloride
Answer:
d. Gold chloride

Question 33.
Explain why Borosilicate Glass is the preferred material for making laboratory equipment like beakers and flasks, rather than Soda-lime glass.
Answer:
Borosilicate Glass is preferred because it contains Boric acid/Boric oxide. This gives it a low coefficient of thermal expansion which makes it highly resistant to heat and thermal shock, preventing it from cracking when heated or cooled rapidly.

Question 34.
Differentiate between Thermoplastics and Thermosetting Plastics based on their ability to be reshaped and provide one example of an object made from each.
Answer:
Thermoplastics: Can be reheated, melted, and reshaped.
Example: Polythene/PVC.
Thermosetting Plastics: Cannot be reheated and melted/reshaped.
Example: Bakelite/Pressure cooker handle.

Question 35.
State and briefly explain the 4R approach that is essential for resolving the problem of plastic pollution in our environment.
Answer:
The 4R Approach is:

1. Refuse: Avoid single-use disposableplastic products.
2. Reduce: Minimise overall plastic usage.
3. Reuse: Find new ways to use plastic products instead of discarding them.
4. Recycle: Convert waste plastic into new usable items through suitable processes.

Question 36.
Analyse the properties of polymers by completing the following table and answering the question below.

Category/Type	Example Polymer	Key Property or Characteristic
Natural Polymer	(i) ____________	A component of wood and paper. A component of wood and paper.
Fibre Polymer	Nylon	(iii)  ____________ (excluding its use in clothing)
Glass Type	Flint Glass	(iii) ____________
Thermoset Plastic	(iv)  ____________	Key Property or Characteristic

Cannot be reheated and molded into a new shape.
What is the primary advantage gained by blending a natural fibre like Cotton with a synthetic fibre like Nylon?
Answer:
(i) Cellulose or Natural Rubber
(ii) Strong and long threads/Low wear and tear/High durability (Any one appropriate property of a fibre)
(iii) High refractive index (Used for lenses and prisms)
(iv) Bakelite or Melamine (Any one appropriate thermoset)
The advantage is to combine the best properties of both. Specifically, it provides the comfort and water absorption of cotton with the strength, durability, or wrinkle resistance of nylon.

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 14 Water Important Questions ensure conceptual clarity.

Water Extra Questions and Answers Class 8 Basic Science Chapter 14 Kerala Syllabus

Water Class 8 Important Questions

Question 1.
Match the property of water in Column A with its definition or consequence in Column B.

Column A	Column B
(i) Surface Tension	(a) Allows many substances to dissolve in it.
(ii) High Heat Capacity	(b) Causes ice to float on water.
(iii) Universal Solvent	(c) Allows water to absorb much heat without a large temperature rise.
(iv) Anomalous Expansion	(d) Force on the water surface minimizing its area.

Answer:
(i) – d, (ii) – c, (iii) – a, (iv) – b

Column A	Column B
(i) Surface Tension	(d) Force on the water surface minimizing its area.
(ii) High Heat Capacity	(c) Allows water to absorb much heat without a large temperature rise.
(iii) Universal Solvent	(a) Allows many substances to dissolve in it.
(iv) Anomalous Expansion	(b) Causes ice to float on water.

Question 2.
Match the condition with its effect on the boiling point of water.

Condition	Effect on Boiling Point
(i) Increased Pressure (e.g., pressure cooker)	(a) Boiling point remains 100°C.
(ii) Decreased Pressure (e.g., high altitude)	(b) Boiling point increases (above 100°C).
(iii) Normal Pressure(sea level, 1 atm)	(c) Boiling point decreases (below 100°C).

Answer:
(i) – b, (ii) – c, (iii) – a

Condition	Effect on Boiling Point
(i) Increased Pressure (e.g., pressure cooker)	(b) Boiling point increases (above 100°C).
(ii) Decreased Pressure (e.g., high altitude)	(c) Boiling point decreases (below 100°C).
(iii) Normal Pressure(sea level, 1 atm)	(a) Boiling point remains 100°C.

Question 3.
Match the type of water hardness with its cause and removal method.

Type of Hardness	Cause / Removal
(i) Soft Water	(a) Caused by chlorides/sulphates; cannot be removed by boiling.
(ii) Temporary Hardness	(b) Soap lathers well; contains few dissolved salts.
(iii) Permanent Hardness	(c) Caused by bi-carbonates; can be removed by boiling.

Answer:
(i) – b, (ii) – c, (iii) – a

Type of Hardness	Cause / Removal
(i) Soft Water	(b) Soap lathers well; contains few dissolved salts.
(ii) Temporary Hardness	(c) Caused by bi-carbonates; can be removed by boiling.
(iii) Permanent Hardness	(a) Caused by chlorides/sulphates; cannot be removed by boiling.

Question 4.
Statement (i): Water has a high surface tension, which helps it wet clothes easily.
Statement (ii): Adding soap or heating water decreases its surface tension.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(c) Statement (ii) is correct, but statement (i) is incorrect. (High surface tension prevents water from wetting clothes easily).

Question 5.
Statement (i): When water freezes to form ice, its volume increases and its density decreases.
Statement (ii): Because ice is denser than water, it floats on water.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(b) Statement (i) is correct, but statement (ii) is incorrect. (Ice floats because it is less dense than water).

Question 6.
Statement (i): The boiling point of water increases as atmospheric pressure decreases.
Statement (ii): Food cooks faster in a pressure cooker because the increased pressure raises the boiling point of water.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(c) Statement (ii) is correct, but statement (i) is incorrect. (Boiling point decreases as pressure decreases).

Question 7.
Why is water called the “universal solvent”?
Answer:
Water is called the universal solvent because it has the ability to dissolve a wide variety of substances, more than many other liquids.

Question 8.
Why does steam at 100°C cause more severe burns than boiling water at 100°C?
Answer:
When water boils and turns into steam at 100°C, it absorbs extra heat energy called latent heat without changing its temperature. This latent heat is used for the change of state. Steam at 100°C contains this additional latent heat energy compared to water at 100°C, so it transfers more heat upon contact, causing more severe burns.

Question 9.
Why does ice float on water, and why is this important for aquatic life?
Answer:
When water freezes, its volume increases (anomalous expansion), causing its density to decrease. Because ice is less dense than liquid water, it floats. This is important because lakes freeze from the top down, forming an insulating layer of ice that prevents the entire water body from freezing, allowing aquatic life to survive underneath.

Question 10.
Describe a simple experiment to distinguish between hard water and soft water using soap.
Answer:
Take two separate flasks or bottles.

• Pour equal amounts of the water samples (one hard, one soft) into each flask.
• Add equal-sized pieces of soap to both flasks.
• Shake both flasks well.
• Observation: The flask containing soft water will produce a good amount of lather (foam). The flask containing hard water will produce very little lather or scum.

Question 11.
How can you demonstrate that the boiling point of water decreases when pressure is reduced?
Answer:

• Fill a boiling tube half with water and boil it using a flame.
• After turning off the flame, immediately close the tube with a rubber cork fitted with a glass tube connected to a syringe.
• Pull back the piston of the syringe.
• Observation: The water inside the tube will start boiling again, even though it has cooled slightly.
• Conclusion: Pulling the piston reduces the pressure inside the tube, which lowers the boiling point, causing the water to boil at the lower temperature.

Question 12.
Describe an activity to demonstrate surface tension using a razor blade or needle.
Answer:
Fill a glass or tumbler completely with still water, perhaps even slightly overfull so the surface bulges.

• Carefully and gently place a clean, dry razor blade or needle flat onto the surface of the water.
• Observation: The blade or needle will float on the surface without sinking, supported by the “skin” created by surface tension.

Question 13.
Water (H₂O) can be decomposed by electrolysis. Write the balanced chemical equation for this reaction.
Answer:

Question 14.
During the electrolysis of water using a Hoffmann voltameter, identify the products formed at the positive electrode (anode) and the negative electrode (cathode).
Answer:
Positive electrode (anode): Oxygen gas (O₂).
Negative electrode (cathode): Hydrogen gas (H₂).

Question 15.
When quicklime (CaO) is added to water (H₂O), slaked lime (Ca(OH)₂) is formed. Write the balanced chemical equation for this reaction.
Answer:
CaO + H₂O → Ca(OH)₂.

Question 16.
What is the chemical formula for a molecule of water, and what does it indicate about the atoms present?
Answer:
The chemical formula is H₂O. It indicates that one molecule of water contains two hydrogen atoms and one oxygen atom.

Question 17.
During the electrolysis of water, twice the volume of hydrogen gas is produced compared to oxygen gas. Based on the formula of water (H₂O), explain why this ratio occurs.
Answer:
The formula H₂O shows that each water molecule contains two hydrogen atoms for every one oxygen atom. When water is split during electrolysis, these atoms combine to form H₂ and O₂ molecules. Since there are twice as many hydrogen atoms available, they form twice the volume (or number of molecules) of hydrogen gas (H₂) compared to oxygen gas (O₂).

Question 18.
What are the chemical formulas for the salts typically responsible for:
a) Temporary hardness (as bicarbonates)
b) Permanent hardness (as chlorides)
Answer:
(a) Calcium bicarbonate: Ca(HCO₃)₂;
Magnesium bicarbonate: Mg(HCO₃)₂.

(b) Calcium chloride: CaCl₂;
Magnesium chloride: MgCl₂.

Question 19.
a.What are the gases liberated in the water voltameter arranged for decomposition of water?
b. Which gas is liberated at the negative pole of the battery?
c. What will be the ratio of the volume of the gases?
Answer:
a. Hydrogen and oxygen
b. Hydrogen
c. Ratio of hydrogen and oxygen – 2 : 1

Question 20.
Heat equal quantity of water and coconut oil in two vessels.
a. The temperature of which liquid will be raised rapidly?
b. Which has more heat capacity?
Answer:
a.Coconut oil
b.water

Question 21.
Take water in a vessel and put a needle on the surface of water carefully.
a. Will the needle be immersed in water. Justify your answer.
b. Why do the water drops assume spherical shape?
Answer:
a. No. Because of the surface tension of water.
b. The surface tension reduces the surface area.

Question 22.
Name two metals which react with cold water.
Answer:
Potassium, sodium

Question 23.
Which is the metal react with hot water? Which is the gas produced? Write the chemical equation.
Answer:
Magnesium; Hydrogen.
Mg + H₂O MgO + H₂

Question 24.
Why does water is known as universal solvent?
Answer:
Since water can dissolves various substances and widely used for preparing solutions it is a universal solvent.

Question 25.
What are hard water and soft water?
Answer:
The water in which soap does not
lather easily is called hard water. Water in which soap gives lather readily is called soft water.

Question 26.
Give the reason for temporary hardness of water.
Answer:
The hardness of water is due to the presence of calcium or magnesium bicarbonate. This type of hardness is called temporary hardness.

Question 27.
Hardness of water is not removed even after it is boiled. What may be the reason for this?
Answer:
This is due to chloride and sulphate of magnesium and calcium are dissolved in water.

Question 28.
Why is air continuously introduced in to the water in an aquarium?
Answer:
Aquatic plants and animals make use of oxygen dissolved in water. Water get polluted as the amount of oxygen in it decreases. Air is introduced in to water to make up the quantity of oxygen.

Question 29.
Write two remedies to prevent water pollution.
Answer:

1. Stop dumping of waste in water resources.
2. Reduce the use of fertilisers and pesticides.

Question 30.
Write two methods to reduce the surface tension of water
Answer:

1. Add soap to water
2. Boil the water.

Question 31.
Complete the given chemical equation.
Mg + H₂O → MgO + …………………
Answer:
H₂

Question 32.
Identify the property of water shown in each of the following situations.
a. Water is used in radiators of automobiles.
b. Small water drops assume spherical shape.
Answer:
a. Heat capacity of water
b.Surface tencsion of water

Question 33.
Two samples of water are given.
Sample 1 – Soap gives lather easily.
Sample 2 – Soap does not give lather easily.
a. Which sample represents hard water?
b. Which among the following salts causes hardness of water?
(Sodium carbonate, Magnesium chloride, Zinc hydroxide, Ammonium chloride)
c. Which type of hardness of water can be removed by boiling?
Answer:
a. Sample 2
b. Magnesium Chloride (MgCl₂)
c. Temporary hardness of water

Question 34.
Water pollution is a burning issue now-a-day.
a. How do aquatic animals and plants get oxygen for respiration?
b. The wastes dumped into rivers and ponds result in the destruction of aquatic life. Explain.
c. Write any other activity that causes water pollution.
Answer:
a. Aquatic animals and plants make use of the oxygen and carbon dioxide dissolved in water.

b. The Wastes dumped in the rivers and Ponds decay using the oxygen dissolved in them. This depletes the amount of oxygen and results in the destruction of aquatic life.

c. Excessive use of detergents Rampant use of fertilizers.

Question 35.
Boling point of water is …………………..
Answer:
100°c.

Question 36.
Following are the observations
when a student added soap solution to two samples of water collected from two different sources.

Sample	Observation
Water collected from source 1	Lathers easily
Water collected from source 2	Does not lather easily

a. Which one of these is hard water?
b. Which salts are responsible for the hardness of water?
Answer:
a. 2.
b. Ca or Mg.

Question 37.
Water is used to cool hot objects. Which property of water is utilised here?
Answer:
Heat capacity of water, (or Specific heat capacity)

Question 38.
Water pollution is a major issue we are facing nowadays. Write any two activities that cause water pollution.
Answer:
Dumping of wastes in water resources Rampant use of fertilizers

Question 39.
Water taken in a round bottomed flask is heated continuously and the temperature is noted.
a. What is the boiling point of water?
b. Eventhough we are heating the flask continuously the temperature remains constant at 100° C. Why?
c. Steam causes more severe burns than boiling water. Why?
Answer:
a. The temperature at which water boils at normal atmospheric pressure is called boiling point of water -100°C

b. Once boiling starts the temperature will not change because all the heat supplied will be used for the change of state.

c. When water starts boiling all the heat supplied will be used for the change of state. Hence all heat supplied will be contained in the steam at the same temperature. So steam causes more severe burns.

Question 40.
Soap is added to two samples of water taken in two test tubes and shaken well.
a. Soap lathers easily in water taken in one test tube. Which type of water is it?
b. Soap does not lather easily in water taken in the second test tube Write the name of a salt which causes this behaviour.
c. Suggest any one method to remove this behaviour of water.
Answer:
a. Soft water
b. Bicarbonates, chlorides and sulphates of calcium and magnesium
c. Temporary hardness is removed by boiling and permanent hardness by any chemical methods.

Question 41.
The volume of water When it solidifies
(increases, decreases, does not change)
Answer:
Increases

Question 42.
Water pollution is a major issue we face today
a. Write down any two situations in which water in your locality gets polluted.
b. Suggest a method to prevent water pollution.
Answer:
a. Plastic thrown into the soil
b. Chemical Pesticides and Chemical fertilizers.

Question 43.
In water from certain sources soap lathers easily. But in water from some other sources soap does lather easily
a. What is the name of water in which soap doesn’t lather easily?
b. Give an example of any salt responsible for this defect of water.
c. Write a method to remove this defect.
Answer:
a. Hard water
b. Bicarbonate, Chloride or Sulphate of Calcium and Magnesium
c. Boil water / add suitable Chemicals

Question 44.
Water is known as the ……………………. solvent.
a) Polar
b) Universal
c) Common
d) Basic
Answer:
b) Universal

Question 45.
Hardness caused by sulphates of calcium and magnesium is known as:
a) Temporary hardness
b) Basic hardness
c) Permanent hardness
d) Chemical hardness
Answer:
c) Permanent hardness

Question 46.
The special force due to the mutual attraction between water molecules that causes the surface to behave like a stretched film is called:
a) Cohesion
b) Adhesion
c) Surface Tension
d) Capillary action
Answer:
c) Surface Tension

Question 47.
Water has its maximum density at ……………………. °C.
a) 0
b) 100
c) 4
d) 37
Answer:
c) 4

Question 48.
When a water solution is tested with litmus paper, it turns blue litmus red. The solution is:
a) Neutral
b) Basic
c) Acidic
d) Alkaline
Answer:
c) Acidic

Question 49.
State any two uses of water’s high heat capacity in daily life.
Answer:
Two uses of high heat capacity:

1. Used as a coolant in car radiators,
2. Helps in maintaining the body temperature within a limit.

Question 50.
How is temporary hardness different from permanent hardness in water?
Answer:
Temporary Hardness is caused by bicarbonates of Calcium/Magnesium and can be removed by boiling. Permanent Hardness is caused by sulphates or chlorides of Calcium/Magnesium and cannot be removed by boiling.

Question 51.
Explain why food takes a longer time to cook in high mountain regions compared to sea level.
Answer:
In high mountain regions, the atmospheric pressure is lower. Since the boiling point is related to pressure, water boils at a temperature lower than 100°C. Cooking takes longer because the cooking medium (water) is at a lower maximum temperature.

Question 52.
Explain why steam causes a more severe burn than boiling water at 100°C.
Answer:
Steam contains more energy than boiling water at the same temperature (100°C). This extra heat is called latent heat of vaporization. When steam condenses on the skin, it releases this large amount of latent heat, causing a much more severe burn.

Question 53.
List three problems caused by water pollution, as mentioned in the chapter.
Answer:
Three problems caused by water pollution: (Any three of the following):

1. Destruction of aquatic plants,
2. Damage to the food chain,
3. Soil pollution,
4. Spread of water-borne diseases (leading to sickness and death).

Question 54.
Explain the Density Anomaly of water and its importance for the survival of aquatic life in cold regions.
Answer:
The maximum density of water is at 4°C. When water is cooled below 4°C and freezes into ice, its volume increases, which means its density decreases. Because ice is less dense than water, it floats on the surface. This floating ice forms an insulating layer that prevents the water underneath from freezing completely, allowing fish and other aquatic life to survive below the surface.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 14 Water Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 14 Water Question Answer Notes

Class 8 Basic Science Chapter 14 Notes Kerala Syllabus Water Question Answer

Water Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
What changes will occur on heating water that has already reached boiling point?
Answer:
When water has reached its boiling point (100°C at 1 atm pressure), further heating will cause it to change state from liquid to gas (steam). The temperature will remain constant at the boiling point during this phase change, as the extra heat energy (latent heat) is used to overcome the forces of attraction between water molecules.

Question 2.
Explain how the boiling point of water varies under the following conditions:
a. In high-altitude areas:
b. At sea level:
c. In vacuum containers:
d. In pressure cookers:
Answer:
a. In high-altitude areas, the atmospheric pressure is lower. A decrease in pres¬sure causes the boiling point of water to decrease (become lower than 100°C).

b. At sea level, the atmospheric pressure is considered normal (approximately 1 atm). Under this standard pressure, the boiling point of water is 100°C.

c. In vacuum containers, the pressure is significantly reduced. This drastic decrease in pressure will cause the boiling point of water to decrease considerably, potentially allowing it to boil even at room temperature or lower.

d. In pressure cookers, steam is trapped, causing the pressure inside to increase. An increase in pressure causes the boiling point of water to increase (become higher than 100°C, e.g., 120°C).

Question 3.
Due to the intermolecular attraction between water molecules, a force arises that tends to minimize the surface area of water. How can this be demonstrated?
Answer:
This force is surface tension. It can be demonstrated in several ways:

1. Floating a Blade/Needle: Gently place a razor blade or a needle flat on the surface of still water. Due to surface tension acting like a stretched skin, the blade/needle can float even though it’s denser than water.
2. Water Striders: Observe insects like water striders walking on the surface of a pond. They distribute their weight, and the surface tension supports them.
3. Spherical Drops: Observe water drop¬lets on a surface that water doesn’t wet (like a lotus leaf or plastic sheet). Surface tension pulls the water into a shape with the minimum possible surface area, which is a sphere.
4. Soap Film Experiment: Dip a wire ring with a thread tied across it into soap solution. Break the soap film on one side of the thread. The surface tension of the remaining film will pull the thread into a curved arc, minimizing the film’s surface area.

Question 4.
Write any three special properties of water and explain situations in daily life where we make use of these properties.
Answer:
High Heat Capacity:
Property: Water can absorb a large amount of heat without a significant rise in its own temperature.
Application: It is used as a coolant in vehicle radiators to absorb excess engine heat and prevent overheating. It also helps regulate body temperature.

Universal Solvent:
Property: Water can dissolve a wide variety of substances.
Application: This allows us to make various solutions for daily use (like salt water, sugar syrup, medicines), enables nutrients to be transported in living organisms (in blood, plant sap), and unfortunately, also contributes to water pollution as harmful substances dissolve in it.

Anomalous Expansion (Ice Floats):
Property: Unlike most substances, water expands when it freezes into ice, making ice less dense than liquid water.
Application: Because ice floats, lakes and rivers freeze from the top down. The surface ice layer insulates the water below, allowing aquatic life to survive during winter in cold climates.

Question 5.
Observe the picture.
Compare the attraction between water molecules and the attraction between water and other substances, and explain why the water level rises inside a glass tube.

Answer:
The picture shows capillary rise.
Forces Involved:
Cohesion: The attraction between water molecules themselves.
Adhesion: The attraction between water molecules and the molecules of the glass tube.
Explanation: In the case of water and glass, the adhesive force (attraction between water and glass) is stronger than the cohesive force (attraction between water molecules). This stronger attraction pulls the water molecules up along the surface of the glass tube, causing the water level inside the narrow tube to rise above the level in the surrounding beaker.

Basic Science Class 8 Chapter 14 Question Answer Kerala Syllabus

Question 1.
Why does the panchayat give importance to the conservation of water resources? (Discussion)?
Answer:
The panchayat gives importance to water conservation because water is essential for the origin and survival of life on Earth. Water is crucial for agriculture, industry, energy production, and transportation. Conserving water bodies like wells, streams, and rivers, which are the wealth of the country, is a collective responsibility to protect this resource from pollution and ensure its availability for vital functions and growth.

Question 2.
Why do people think that if there is water, there is a possibility of life? (Discussion)
Answer:
People believe that where there is water, there is a possibility of life because water is the precious gift of nature responsible for the origin and survival of life on Earth. Water is essential for all vital functions in living organisms, such as respiration, digestion, and excretion, as well as maintaining body temperature and keeping eyes moist. Plants also need it for growth and photosynthesis. This fundamental necessity is why scientists search for water when looking for life on other planets.

Question 3.
What are the uses of water?
Answer:

1. For drinking.
2. For bathing.
3. For cooking.
4. It’s also essential for vital functions like respiration, digestion, and excretion, regulating body temperature, and keeping eyes moist.
5. It’s needed for plant growth and photosynthesis.
6. It is crucial for agriculture, industry, energy production, and transportation.

Question 4.
Why can water be used for so many purposes?
Answer:
Water can be used for so many purposes primarily because of its special property as a universal solvent. Water can dissolve a wide variety of substances, and the nature of the water changes depending on what is dissolved in it, allowing it to be used to make different types of solutions. This solubility is one of solubility is one of the main reasons for its varied uses.

Textbook Page No : 235 & 236

Question 5.
Complete the Table (Table 14.1 – Litmus Test)

Answer:

Pure Water / Substance Added to Water	Blue / Red Litmus Paper Experiment – Observation	Inference
Pure Water	No change in the colour of the litmus paper	Water has no acidic or basic property.
Common Salt	No change	Common Salt solution is Neutral
sugar	No change	Sugar solution is Neutral
honey	No change	Honey solution is Neutral
vinegar	Turns blue litmus red	Vinegar solution is Acidic
Soap Powder	Turns red litmus blue	Soap Powder solution is Basic
Lime juice	Turns blue litmus red	Lime juice solution is Acidic
Sodium hydroxide (Alkali)	Turns red litmus blue	Sodium hydroxide solution is Basic

Question 6.
What could be the reason for the hardness of water? (Discussion)
Answer:
The hardness of water is caused by dissolved salts that water picks up as it flows through the soil. Specifically, the hardness is caused by some salts of metals like magnesium and calcium. If the hardness is caused by bicarbonates of calcium and magnesium, it is temporary hardness. If it is caused by sulphates or chlorides of metals such as magnesium or calcium, it is permanent hardness.

Question 7.
Complete the Table (Table 14.2 – Hardness Test)

Answer:

Substance added to water	Soap lathers well/ Doesn’t lather well	Conclusion
Pure water (nothing added)	Lathers well	Pure water is soft water.
Magnesium bicarbonate/ Calcium bicarbonate	Doesn’t lather well	These salts cause hardness.

Question 8.
How does the water level appear inside the glass tube? (Question from Experiment)
Answer:
The water level inside the thin glass tube appears to be higher than the water level in the beaker. This phenomenon is due to capillary action.

Textbook Page No : 237

Question 9.
Now pour a little water on a leaf of colocasia. Does it wet the surface?
Answer:
No, the water does not wet the surface of the colocasia leaf easily.
Explanation: The reason is that the molecules in the leaf and the water molecules have very little attraction between them (poor adhesion).

Question 10.
Can you list some materials around you that water cannot wet? (Discussion)
Answer:
Water does not wet a surface when the attraction between the molecules in the surface and the water molecules is very little.
Materials that water cannot easily wet (hydrophobic materials) include:

1. A colocasia leaf.
2. Waxy or oily surfaces (like a car that’s been waxed).
3. Plastic or synthetic materials (like a plastic sheet, which is why drops are spherical).
4. Teflon (used in non-stick pans).
5. The feathers of some water birds due to their oily coating.

Question 11.
What is the shape of the water drops (on a plastic sheet)?
Answer:
If a surface is not getting wet, the water drops will be spherical in shape. This occurs because the attraction between water molecules (cohesion) is stronger than the attraction between water and the surface (adhesion).

Question 12.
Why is the water surface behaving like this (when coins are added)?
Answer:
The water surface will appear to bulge or rise above the rim of the beaker, behaving like a stretched, elastic film or membrane.

Question 13.
Why is the water surface behaving like this?
Answer:
The water surface is behaving like this due to surface tension. The mutual attraction between water molecules causes a force to act on the water surface, making it behave like a stretched film.

Question 14.
Why can some insects walk on the surface of water?

Answer:
Insects can walk on water because of surface tension. The mutual attraction between water molecules creates a force that makes the water surface behave like a stretched, flexible film, which is strong enough to support the light weight of the insects.

Question 15.
Gently place a blade on the surface of water. Can you explain why the blade stays on top without sinking?

Answer:
The blade stays on top of the water without sinking because of surface tension. The mutual attraction between water molecules creates a force at the water surface that makes it behave like a stretched film. This stretched film is strong enough to support the light weight of the blade without breaking.

Textbook Page No : 238 & 239

Question 16.
From the figure can you say in which direction the force acts on the water molecules on the surface? (Discussion)
Answer:
Based on the text explaining surface tension, the force acts on the water molecules on the surface in a direction that tries to minimize the surface area. This force is an inward pull (towards the bulk of the liquid), which causes the surface to behave like a stretched film.

Question 17.
What is the shape of the soap film now (after breaking it on one side of the thread)?
Answer:
When the soap film on one side of the thread is broken, the remaining film on the other side will pull the thread, causing the thread to take a circular or curved shape that maximizes the area of the side where the film remains, and minimizes the area of the film itself. The intact film pulls the thread to try and reduce its own surface area.

Question 18.
Is it easier to clean dirty clothes with plain water or with soap water? Clothes get cleaner in cold water or hot water? (Discussion)
Answer:
It is easier to clean dirty clothes with soap water and hot water.

• Plain water has a high surface tension, meaning it doesn’t easily wet the clothes.
• When you add soap or heat the water, the surface tension decreases.
• This decrease in surface tension allows the water to wet the clothes better and clean them more easily, helping the water penetrate the fabric and lift the dirt.

Question 19.
What change happens to water at this point (when temperature stops increasing despite continued heating)?
Answer:
At this point, the water starts to boil. The water molecules begin to change their state from liquid to gas (steam). This temperature is the boiling point of water, which is 100°C (at normal atmospheric pressure).

Question 20.
Why doesn’t the temperature rise once the water starts boiling?
Answer:
Once water starts boiling, the temperature doesn’t rise because the extra heat energy is used to overcome the force of attraction between the water molecules. In other words, the heat is used for the change of state (liquid to gas) rather than to increase the temperature of the liquid water.

Question 21.
Which contains more energy boiling water or steam? Which can cause severe burn? Boiling water or steam? (Discussion)
Answer:
Steam contains more energy than boiling water. The extra heat energy (called latent heat of vaporization) added to boiling water to turn it into steam without increasing the temperature is stored in the steam. Therefore, steam can cause a more severe burn. When steam condenses back into liquid water on the skin, it releases that extra latent heat, causing a much more intense burn than boiling water at 100°C.

Textbook Page No : 240

Question 22.
Why does cooking in open vessels take more time in high mountain regions? (Discussion)
Answer:
In high mountain regions, the atmospheric pressure is lower because height increases as pressure decreases. Since the boiling point of a liquid is related to atmospheric pressure, when the pressure decreases, the boiling point of water also decreases. This means water boils at a temperature lower than 100°C. Food takes longer to cook because the boiling water, the medium of cooking, is at a lower maximum temperature.

Question 23.
What change happens to the boiling point when pressure increases? How does cooking become easier in pressure cookers?
Answer:

• When pressure increases, the boiling point of water increases.
• Cooking becomes easier in pressure cookers because they are sealed and the steam cannot escape. As a result, the pressure inside increases. This increased pressure raises the boiling point of the water well above 100°C. Cooking at a higher temperature significantly reduces the cooking time.

Question 24.
When the same amount of heat is given to water and coconut oil, which one’s temperature rises faster in a fixed time? Why?
Answer:
The coconut oil’s temperature will rise faster.

• This is because water is a liquid with a very high heat capacity.
• Heat capacity is the amount of heat energy required to raise the temperature of a given substance by 1 °C.
• Due to its high heat capacity, the temperature of water does not rise quickly.

Question 25.
How can we make use of high heat capacity of water?
Answer:
The high heat capacity of water is utilized in the following ways:

• Water is used to cool hot objects.
• The radiators in vehicles use a mixture containing a special coolant and water to cool the engine.
• Water helps in maintaining the body temperature within a limit.

Textbook Page No : 241

Question 26.
In which state is oxygen usually seen? What about hydrogen? But in which state is water usually found?
Answer:

• Oxygen is usually seen in the gaseous state.
• Hydrogen is usually seen in the gaseous state.
• Water is usually found in the liquid state.

Question 27.
What could be the reason for water to occur in the liquid state?
Answer:
The reason water occurs in the liquid state at room temperature, even though its components (hydrogen and oxygen) are gases, is the existence of a special kind of attractive force between water molecules. This attractive force is strong enough to keep the water in a liquid form at room temperature.

Question 28.
Now think, what would happen if this force between water molecules did not exist?
Answer:
If the attractive force between water molecules did not exist, water would stay only in the gaseous state. The gas would not condense to form liquid water, meaning there would be no rivers, no seas, and probably no living things on earth.

Textbook Page No : 242

Question 29.
What happened to the volume of the water in the bottle when it turned into ice?
Answer:
When water turns into ice, its volume increases. This is an unusual property for a substance when cooled.

Question 30.
Can you now explain why a piece of ice floats on the surface of water when you put it in water?
Answer:
A piece of ice floats on the surface of water because its density decreases when it turns from liquid water into solid ice. This is because, unlike most substances, the volume of water increases when it freezes. Since density is mass divided by volume (D = m/V), an increase in volume for the same mass results in a lower density. Since the density of ice is less than that of liquid water, it floats.

Question 31.
What if the water in rivers and lakes there turns completely into ice? Wouldn’t aquatic life get trapped in the ice and die? Does that happen? What could be the reason?
Answer:
Aquatic life generally does not get trapped and die because the rivers and lakes do not freeze completely from top to bottom. The reason is:

• The maximum density of water is at 4°C. As the surface water cools to 4°C, it sinks, and warmer water rises.
• Once the surface water cools below 4°C and starts freezing, its volume increases, and its density decreases.
• This less-dense ice (and near-freezing water) floats on top, forming an insulating layer that protects the underlying water from freezing completely. This allows fish and other aquatic life to survive in the colder regions.

Textbook Page No : 243

Question 32.
What could be the reasons for water pollution?
Answer:

• Chemicals from agricultural fields.
• Chemicals from factories.
• Oils from vehicles.
• Other reasons not explicitly listed but implied by the images are dumping of solid waste into water bodies and the release of untreated sewage/industrial discharge.

Question 33.
What are the main problems caused by water pollution?
Answer:

• Destruction of aquatic plants.
• Damage to the food chain.
• Soil pollution.
• Diseases.
• Millions of people suffer from water-borne diseases every year, leading to many deaths, and a lack of access to clean water.

Class 8 Basic Science Chapter 14 Question Answer Extended Activities

Question 1.
Investigate and prepare a study report on the efforts taken in your locality to conserve water sources.

Question 2.
Based on rainfall availability across Kerala, prepare a rainfall distribution map.

Water Class 8 Notes

Class 8 Basic Science Water Notes Kerala Syllabus

The Importance of Water
Water is a precious gift of nature, and its conservation is a collective responsibility. The presence of water is what scientists look for on other planets (like the Moon) as evidence for the possibility of life.

Why water is essential:

• For Life (ജീവന്റെ നിലനിൽപ്പിന്):
  1. Water is responsible for the origin and survival of life on Earth.
  2. It’s essential for vital bodily functions like respiration, digestion, and excretion.
  3. It helps to regulate body temperature and keeps the eyes moist.
  4. Plants need water for growth and photosynthesis.
• For Development (വികസനത്തിന്):
  • Water is crucial for agriculture, industry, energy production, and transportation.
• Daily Uses: We use water for drinking, bathing, cooking, and many other purposes.

ഭൂമിയിലെ ജീവന്റെ ഉത്ഭവത്തിനും നിലനിൽപ്പിനും ജലം അത്യന്താപേക്ഷിതമാണ്. ദഹനം, ശ്വസനം തുടങ്ങിയ ശാരീരിക പ്രവർത്തനങ്ങൾക്കും കൃഷി, വ്യവസായം, ഊർജ്ജ ഉത്പാദനം തുടങ്ങിയ കാ ര്യങ്ങൾക്കും ജലം കൂടിയേ തീരൂ. അതിനാൽ, നമ്മുടെ ജലസ്രോതസ്സുകളെ (കിണറുകൾ, പുഴ കൾ) മലിനീകരണത്തിൽ നിന്ന് സംരക്ഷിക്കേണ്ട ത് നമ്മുടെ എല്ലാവരുടെയും ഉത്തരവാദിത്തമാണ്.

Characteristics of Water: Solubility (ജലത്തിന്റെ സവിശേഷത ലായകത്വം)
One of the most important characteristics of water is its ability to dissolve many other substances.

• Universal Solvent (സാർവിക ലായകം):
  • “Since water can dissolve a wide variety of substances, it is known as universal solvent”.
• Nature of Pure Water:
  • Observation: Pure water shows no change in the colour of blue or red litmus paper.
  • Inference: This means pure water has no acidic or basic property; it is neutral.
• Nature of Solutions:
  • The nature of water changes depending on the substances dissolved in it. If you dissolve an acid (like vinegar), the solution becomes acidic. If you dissolve a base (like soap), the solution becomes basic.

ധാരാളം പദാർത്ഥങ്ങളെ ലയിപ്പിക്കാൻ (dissolve) ജലത്തിന് കഴിവുണ്ട്. ഈ സവിശേഷതകൊ ണ്ടാണ് ജലത്തെ “സാർവിക ലായകം’ (Universal Solvent) എന്ന് വിളിക്കുന്നത്. ശുദ്ധജലം (Pure water) നിർവീര്യമാണ് (netural), അതായത് ഇതിന് ആസിഡിന്റെയോ ബേസിന്റെയോ സ്വഭാ വമില്ല. എന്നാൽ ജലത്തിൽ ലയിക്കുന്ന പദാർത്ഥം ഏതാണോ, അതിനനുസരിച്ച് ആ ലായനിയുടെ സ്വഭാവം (ആസിഡ് ബേസ്) മാറുന്നു.

Litmus Test Observations (Indicating pH Nature)

Substance Added to Water	Inference
Pure Water, Common Salt, Sugar, Honey	Neutral (No change in litmus paper color)
Vinegar, Lime juice	Acidic (Turns blue litmus red)
Soap Powder, Sodium hydroxide	Basic (Alkaline) (Turns red litmus blue)

Hard Water and Soft Water (കഠിനജലവും മൃദുജലവും)

• Soft Water: Water in which soap lathers well. Example: Rainwater.
• Hard Water: Water in which soap does not lather well. Example: Bore well water.
• Cause of Hardness: As water flows through the soil, salts of metals like magnesium and calcium dissolve in it. These dissolved salts make the water hard.

സോപ്പ് എളുപ്പത്തിൽ പതയുന്ന ജലമാണ് മൃദു ജലം (ഉദാ: മഴവെള്ളം). സോപ്പ് എളുപ്പത്തിൽ പ തയാത്ത ജലമാണ് കഠിനജലം (ഉദാ: കിണറ്റിലെ വെള്ളം). ജലം മണ്ണിലൂടെ ഒഴുകുമ്പോൾ, കാൽ സ്യം, മഗ്നീഷ്യം എന്നിവയുടെ ലവണങ്ങൾ (salts) അതിൽ ലയിക്കുന്നതാണ് ജലം കഠിനമാകാൻ കാരണം.

Types of Hardness

Type of Hardness	Cause	Removal Method
Temporary Hardness	Bicarbonates of calcium and magnesium	Removed by boiling the water.
Permanent Hardness	Sulphates or chlorides of metals such as magnesium or calcium	Cannot be removed by boiling.

Capillary Rise

• Capillary Rise (Fig 14.3): The water level inside a thin glass tube is higher than the water in the beaker.

Reason: Aattraction between water and glass is stronger than the attraction between water and water, so the water is “pulled up” the glass tube.

• Water on a Leaf (Fig 14.4): Water forms spherical drops on a colocasia (ചേസില) leaf and does not wet it.

Reason: Attraction between water and the leaf is very weak. Therefore, the water’s its attraction to itself is stronger, pulling the water into a tight, spherical drop.

Surface Tension (പ്രതലബലം)

• The surface of the water behaves like a stretched film or membrane.
• “Due to the mutual attraction (cohesion) between water molecules, a force acts on the water surface, making its surface area as small as possible. This force is called surface tension.”
• Surface Tension and Cleaning:
  1. Water has a high surface tension, which prevents it from “wetting” clothes easily.
  2. To clean clothes, we need to reduce this tension. We can do this by:
     • Adding soap or detergent
     • Heating the water (using hot water)
  3. This decreases the surface tension, allowing the water to soak into the fabric and clean more effectively.

Boiling Point (തിളനില)

• The boiling point is the specific temperature at which a liquid (like water) starts to change into a gas (steam).
• Boiling Point of Water: 100°C.
• Phenomenon: When water reaches 100°C and starts to boil, its temperature stops increasing, even if you continue to add more heat.
• Reason: This extra heat energy is not used to raise the temperature. It is used to overcome the forces of attraction between the molecules and complete the change of state from liquid to gas.
• Application:
  1. Steam (at 100°C) contains more energy than boiling water (at 100°C) because it holds this extra “hidden” heat.
  2. This is why steam causes more severe burns than boiling water.

ജലം തിളയ്ക്കുമ്പോൾ (100°C-ൽ), നാം തുടർ ന്നും ചൂട് നൽകിയാലും അതിന്റെ താപനില (temperature) കൂടുന്നില്ല. ഈ അധിക ഊർജ്ജം ഉപയോഗിക്കുന്നത് ജലം നീരാവിയാക്കി (change of state) മാറ്റാനാണ്. ഈ ‘ഒളിഞ്ഞിരി ക്കുന്ന’ ഊർജ്ജം (ലീനതാപം) കൂടി നീരാവിയി ൽ ഉള്ളതുകൊണ്ടാണ്, തിളച്ച വെള്ളത്തേക്കാൾ കൂടുതൽ പൊള്ളൽ നീരാവി ഏൽപ്പിക്കുന്നത്.

Pressure and Boiling Point (മർദ്ദവും തിളനിലയും)
□ The boiling point of a liquid is directly related to the atmospheric pressure acting on it.

□ Standard Boiling Point: The boiling point of water is 100°C at the normal atmospheric pressure of 1 atmosphere (1 atm).

□ Relationship:

1. Pressure Decreases → Boiling Point Decreases:

• Experiment (Fig 14.8): Water is boiled and the flame is turned off. When the piston of a syringe is pulled back, the pressure inside the tube decreases. This causes the water to start boiling again, even at a lower temperature.
• Application: In high mountain regions, the atmospheric pressure is low. Because pressure is low, water boils at a lower temperature (e.g., 80°C or 90°C). This temperature is not high enough to cook food properly, so cooking takes more time.

2. Pressure Increases → Boiling Point Increases:
Application (Pressure Cooker, Fig 14.9): A pressure cooker traps the steam, not allowing it to escape. This causes the pressure inside to increase significantly. Because the pressure is high, the boiling point of the water increases (e.g., to 120°C). Food cooks much faster at this higher temperature.
മർദ്ദം (Pressure) കൂടുമ്പോൾ തിളനില (Boiling Point) കൂടുന്നു; മർദ്ദം കുറയുമ്പോൾ തിളനില കുറയുന്നു.

പ്രഷർ കുക്കർ. ഇതിനുള്ളിൽ മർദ്ദം കൂടുന്നതുകൊ ണ്ട്, ജലം 100°C യിലും ഉയർന്ന താപനിലയിൽ (e.g., 120°C) തിളയ്ക്കുന്നു. ഇത് ആഹാരം വേഗത്തിൽ പാകം ചെയ്യാൻ സഹായിക്കുന്നു.

ഉയർന്ന മലനിരകൾ; അവിടെ മർദ്ദം കുറവായതിനാ ൽ, ജലം 100°C യിലും താഴ്ന്ന താപനിലയിൽ തിളയ്ക്കുന്നു. അതുകൊണ്ട് ആഹാരം പാകമാ കാൻ കൂടുതൽ സമയം എടുക്കുന്നു.

Heat Capacity of Water (ജലത്തിന്റെ തിളനിലയും)

• Observation: When the same amount of heat is given to equal masses of water and coconut oil, the coconut oil’s temperature rises faster. The water’s temperature rises very slowly.
• Reason: Water has a very high heat capacity.
• Heat capacity is the amount of heat energy required to raise the temperature of a given substance by 1°C.
• Applications:
  Because water can absorb a large amount of heat without its own temperature rising quickly, it is an excellent coolant.
  1. Vehicle Radiators: Water is used in radiators to absorb the excess heat from the engine.
  2. Regulating Body Temperature: The water in our bodies helps to maintain a stable internal temperature.

The Special Case of Ice (Anomalous Expansion)

• Normal Behavior: When most substances cool, their volume decreases.
• Water’s Behavior: When water cools and turns into ice, its volume increases.
• Density: Since Density = Mass / Volume, when the volume increases for the same mass, the density of ice decreases.
• Result: Because ice is less dense than water, a piece of ice floats on the surface of water.
• Importance for Aquatic Life:
  In cold countries, when lakes and rivers freeze, the ice (being less dense) forms on the top surface. This ice layer acts as a blanket, insulating the water below and preventing the entire lake from freezing solid. This allows fish and other aquatic life to survive in the liquid water underneath.
• Effect of Solutes on Boiling Point
  1. Observation: The boiling point of water with added substances (like salt) is higher than the boiling point of pure water (100°C).
  2. Reason: When salt is added, more energy is required to boil the water. This is known as boiling point elevation.

Structure and States of Water

• Molecular Structure: A water molecule is made up of two hydrogen atoms and one oxygen atom (H₂O).

• States: Water is a natural substance that can exist in all three states: solid (ice), liquid (water), and gas (steam).
• Liquid State Reason: A special kind of attractive force exists between water molecules. This force is responsible for surface tension and helps water keep its liquid form at room temperature, even though hydrogen and oxygen are gases.

A. Electrolysis

• Water can be split back into hydrogen and oxygen by a process called electrolysis.
• Using the Hoffman water voltameter

• hydrogen is produced at the negative Problems caused by Water Pollution: electrode and oxygen is produced at the positive electrode.

B. Density Anomaly (Unusual Property of Freezing)

• Maximum Density: The maximum density of water is at 4°C.
• Volume Change: When water is cooled or heated from 4C, its volume increases. When water turns into ice (cooled from 4°C to 0°C), its volume increases, and therefore its density decreases.
• Ice Floats: Since ice is less dense than liquid water, it floats on the surface.
• Survival of Aquatic Life: This floating layer of ice acts as an insulator, protecting the underlying water from freezing completely, allowing fish and other living things to survive in cold regions.

C. Effect of Dissolved Substances on Boiling Point

• The boiling point of water with added substances (like salt) is higher than that of pure water.
• This is because more energy is required to boil the water when a substance is added.

Water Pollution ((ജലമലീനീകരണം))
Water’s ability to dissolve many substances (as a universal solvent) also means it can easily become polluted.
Causes/Sources of Pollution:

• Chemicals from agricultural fields
• Chemicals from factories
• Oils from vehicles
• Improper waste disposal (dumping garbage, plastic)
• Sewage discharge

Problems Caused by Water Pollution:

• Destruction of aquatic plants
• Damage to the food chain
• Soil pollution
• Spread of water-borne diseases

Pure water is a basic human need, and millions suffer from diseases due to a lack of it, reinforcing the idea: “Right to water is a birthright”.

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 13 Acids, Bases, Salts Important Questions ensure conceptual clarity.

Acids, Bases, Salts Extra Questions and Answers Class 8 Basic Science Chapter 13 Kerala Syllabus

Acids, Bases, Salts Class 8 Important Questions

Question 1.
Which organic acid is responsible for the sour taste in tamarind?
a) Citric acid
b) Lactic acid
c) Acetic acid
d) Tartaric acid
Answer:
d) Tartaric acid

Question 2.
Which is the common component present in all acids that is responsible for their acidic properties?
a) Oxygen
b) Hydrogen
c) Chlorine
d) Sulphur
Answer:
(b) Hydrogen.

Question 3.
Substances that can increase the
concentration of hydroxide ions (OH^–) in an aqueous solution are called:
a) Acids
b) Salts
c) Alkalis
d) Non-metal oxides
Answer:
(c) Alkalis.

Question 4.
When an acid reacts with a highly reactive metal (like Zinc), it produces a gas. How is this gas identified?
a) It turns lime water milky.
b) It turns blue litmus red.
c) It puts out a burning matchstick with a ‘pop’ sound.
d) It forms a brown ring.
Answer:
(c) It puts out a burning matchstick with a ‘pop’ sound (This is the test for Hydrogen, H₂).

Question 5.
Statement 1: Acids have a sour taste and turn blue litmus red.
Statement 2: Bases have a bitter taste and turn red litmus blue.
a) Both statements are correct.
b) Only Statement 1 is correct.
c) Only Statement 2 is correct.
d) Both statements are incorrect.
Answer:
(a) Both statements are correct.

Question 6.
Statement 1: Metal oxides (like MgO) generally show basic properties.
Statement 2: Non-metal oxides (like CO₂) generally show acidic properties.
a) Both statements are correct.
b) Only Statement 1 is correct.
c) Only Statement 2 is correct.
d) Both statements are incorrect.
Answer:
(a) Both statements are correct.

Question 7.
Statement 1: A solution with a pH value of 3 is acidic.
Statement 2: A solution with a pH value of 9 is also acidic.
a) Both statements are correct.
b) Only Statement 1 is correct.
c) Only Statement 2 is correct.
d) Both statements are incorrect.
Answer:
(b) Only Statement 1 is correct. (Statement 2 is incorrect; pH > 7 is basic).

Question 8.
Classify the following substances as Acidic, Basic, or Neutral:
(Lemon juice, Soap solution. Water, Vinegar, Lime water)
Answer:
Acidic: Lemon juice, Vinegar.
Basic: Soap solution, Lime water (Calcium hydroxide).
Neutral: Water.

Question 9.
Match the food substance with the organic acid responsible for its sour taste.

Substance	Acid
1. Tamarind	a. Lactic acid
2. Vinegar	b. Citric acid
3. Yoghurt	c. Tartaric acid
4. Lemon juice	d. Acetic acid

Answer:
1 – c, 2 – d, 3 – a, 4 – b.

Substance	Acid
1. Tamarind	c. Tartaric acid
2. Vinegar	d. Acetic acid
3. Yoghurt	a. Lactic acid
4. Lemon juice	b. Citric acid

Question 10.
Find the acid and base that must be reacted to obtain the salt Sodium Sulphate (Na₂SO₄).
Answer:
Acid: Sulphuric acid (H₂SO₄)
Alkali/Base: Sodium hydroxide (NaOH)

Question 11.
Find and correct the error in this statement:
“Acids turn red litmus paper blue, and bases turn blue litmus paper red.”
Answer:
Error: The colors are swapped. Correction: Acids turn blue litmus paper red, and bases turn red litmus paper blue.

Question 12.
Find and correct the error in this statement:
“A pH value of 8 indicates an acidic solution.”
Answer:
Error: Acidic.
Correction: A pH value greater than 7 indicates a basic solution.

Question 13.
Find and correct the error in this statement:
“When acids react with carbonates (like marble), hydrogen gas is liberated.”
Answer:
Error: Hydrogen gas.
Correction: When acids react with carbonates, carbon dioxide gas (CO₂) is liberated.

Question 14.
Why does taking an antacid (like milk of magnesia) relieve indigestion or heartburn?
Answer:
Indigestion is often caused by excess hydrochloric acid (HCl) in the stomach. Antacids (like milk of magnesia, Mg(OH)₂) are bases. The base reacts with the excess acid in a neutralisation reaction, reducing the acidity and providing relief.

Question 15.
Why is soda water considered acidic?
Answer:
Soda water is made by dissolving carbon dioxide (CO₂) (a non-metal oxide) in water. The CO₂ reacts with the water (H₂O) to form carbonic acid (H₂CO₃), which gives soda water its acidic nature.

Question 16.
Why do farmers sometimes add slaked lime (calcium hydroxide) to agricultural soil?
Answer:
Farmers add slaked lime (a base) to reduce the acidity of acidic soil. This neutralisation reaction helps bring the soil pH to a level that is suitable for growing certain crops.

Question 17.
Complete the chemical equation for the dissociation of Sulphuric acid in water:
H₂SO₄ → ……………..+…………..
Answer:
H₂SO₄ → 2H⁺ + SO₄^2-.

Question 18.
Complete the chemical equation for the neutralisation reaction between dilute nitric acid and sodium hydroxide.
NaOH + HNO₃ → ……………..+…………..
Answer:
NaOH + HNO₃ → NaNO₃ + H₂O. (The products are a salt, Sodium Nitrate, and water).

Question 19.
A salt solution forms a white precipitate when Barium Chloride (BaCl₂) is added. This precipitate does not dissolve when dilute HCl is added. Which ion is present in the salt? (Sulphate ion or Carbonate ion?)
Answer:
The Sulphate ion (SO₄^2-). (Both ions form a white precipitate with BaCl₂, but only Barium Sulphate (BaSO₄) does not dissolve in HCl).

Question 20.
Describe the experiment to identify a carbonate salt.
Answer:
Take a little of the salt solution (e.g., sodium carbonate) in a test tube.
Add a few drops of dilute hydrochloric acid (HCl).
Observation 1: Bubbles (effervescence) will form, indicating a gas is liberated.
Confirmation: Pass this gas through clear lime water (Ca(OH)₂ solution) using a delivery tube.
Observation 2: The clear lime water will turn milky. This confirms the gas is Carbon Dioxide (CO₂) and the salt is a carbonate.

Question 21.
Describe the procedure to test if a salt (like KCl) contains the chloride ion (Cl ).
Answer:
Take a small amount of the salt solution (e.g., KCl) in a test tube.
Add a few drops of silver nitrate (AgNO₃) solution to it.
Observation: A white precipitate of silver chloride (AgCl) will be formed.

Question 22.
Describe the procedure to test if a salt (like Ammonium Sulphate) contains the sulphate ion (SO₄^2-).
Answer:
Take a small amount of the salt solution in a test tube and mix it with water. Add barium chloride (BaCl₂) solution to it.
Observation 1: A white precipitate (Barium Sulphate, BaSO₄ will form.
Confirmation: Add a few drops of dilute hydrochloric acid (HCl) to the precipitate.
Observation 2: The white precipitate will not dissolve.

Question 23.
Match the food substance in Column A with the acid it contains in Column B.

Column A	Column B
(i) Vinegar	(a) Lactic acid
(ii) Lemon juice	(b) Tartaric acid
(iii) Yoghurt	(c) Acetic acid
(iv) Tamarind	(d) Citric acid

Answer:
(i) – c, (ii) – d, (iii) – a, (iv) – b

Column A	Column B
(i) Vinegar	(c) Acetic acid
(ii) Lemon juice	(d) Citric acid
(iii) Yoghurt	(a) Lactic acid
(iv) Tamarind	(b) Tartaric acid

Question 24.
Match the common name in Column A with its chemical formula in Column B.

Column A	Column B
(i) Caustic soda	(a) Ca(OH)2
(ii) Milk of lime	(b) KOH
(iii) Caustic potash	(c) NaOH

Answer:
(i) – c, (ii) – a, (iii) – b

Column A	Column B
(i) Caustic soda	(c) NaOH
(ii) Milk of lime	(a) Ca(OH)2
(iii) Caustic potash	(b) KOH

Question 25.
Match the ion being tested with the correct observation.

Ion	Observation
(i) Chloride (Cl–)	(a) Bubbles of gas that turn lime water milky.
(ii) Sulphate (SO42-)	(b) A brown ring forms at the liquid junction.
(iii) Carbonate (CO32-)	(c) A white precipitate forms when silver nitrate is added.
(iv) Nitrate (NO3–)	(d) A white precipitate forms when barium chloride is added.

Answer:
(i) – c, (ii) – d, (iii) – a, (iv) – b

Ion	Observation
(i) Chloride (Cl–)	(d) A white precipitate forms when barium chloride is added.
(ii) Sulphate (SO42-)	(a) Bubbles of gas that turn lime water milky.
(iii) Carbonate (CO32-)	(b) A brown ring forms at the liquid junction.
(iv) Nitrate (NO3–)	(c) A white precipitate forms when silver nitrate is added.

Question 26.
Statement (i): Acids have a sour taste and turn red litmus blue.
Statement (ii): Bases have a bitter taste and turn blue litmus red.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(d) Both statements are incorrect. (Acids turn blue to red, and bases turn red to blue).

Question 27.
Statement (i): The chemical reaction between an acid and a base to form salt and water is called neutralisation.
Statement (ii): A solution with a pH value of 7 is considered basic.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(b) Statement (i) is correct, but statement (ii) is incorrect. (A pH of 7 is neutral).

Question 28.
Statement (i): Non-metal oxides (like CO₂) react with water to form substances that are generally acidic.
Statement (ii): Metal oxides (like MgO) react with water to form substances that are generally basic.
a) Both statements (i) and (ii) are correct.
b) Statement (i) is correct, but statement (ii) is incorrect.
c) Statement (ii) is correct, but statement (i) is incorrect.
d) Both statements (i) and (ii) are incorrect.
Answer:
(a) Both statements (i) and (ii) are correct.

Question 29.
What is the chemical definition of an acid, and what ion is the basis for all its general properties?
Answer:
Acids are substances that can increase the concentration of hydrogen ions (H⁺) in an aqueous solution. The H⁺ ion (or hydronium ion, H₃O⁺) is the basis for the general properties of acids.

Question 30.
Match the following appropriately.

Substances	Acid responsible for the sour taste
a. Lemon juice	i) Acetic acid
b.Yoghurt / Buttermilk	ii) Tartaric acid
c. Tamarind	iii) Citric acid
d.Vinegar	iv) Lactic acid

A. a – (ii) c – (iii), d – (iv) b – (i)
B. a – (i) (b) – (ii), c – (iii), d – (iv)
C. a – (iii), b – (ii) c – (iv) d – (i)
D. a – (iii), b – (iv), c – (ii) d – (i)
Answer:
D. a – (iii) b – (iv) c – (ii) d – (i)

Substances	Acid responsible for the sour taste
a. Lemon juice	iii) Citric acid
b.Yoghurt / Buttermilk	iv) Lactic acid
c. Tamarind	ii) Tartaric acid
d.Vinegar	i) Acetic acid

Question 31.
From the characteristics given below, find out those suitable for acids.
a) Turns blue litmus red
b) Soapy to touch
c) Have bitter taste
d) Have sour taste
(i) a, b
(ii) b, c
(iii) a, d
(iv) a, c
Answer:
(iii) a, d

Question 32.
Why are antacids, like Milk of Magnesia (magnesium hydroxide), used to treat indigestion?
Answer:
Indigestion is often caused by an excess of hydrochloric acid in the stomach. Antacids are basic substances.

They undergo a neutralisation reaction with the excess acid, reducing the acidity and providing relief.

Question 33.
Why does a farmer add slaked lime (calcium hydroxide) to soil that has a pH value of 5?
Answer:
A pH value of 5 is acidic (since it is less than 7). Slaked lime is a base. The farmer adds it to the soil to neutralize the excess acidity, making the soil suitable for growing crops.

Question 34.
Soda water is prepared by dissolving CO₂ gas under high pressure in water.
A. Which is the acid present in soda water? What is its chemical formula?
B. Write the chemical equation of the reaction.1
Answer:
A. Carbonic acid.
H₂CO₃
B. H₂O + CO₂ → H₂CO₃

Question 35.
Acid rain causes many environmental problems.
a) Explain how acid rain is formed.
b) Write any one environmental issue caused by acid rain.
Answer:
a) The gases like SO₂, NO₂ emitted from factories, motor vehicles thermoelectric power stations into air dissolve in rain water and cause acid rain.

b)

• Plants lose their ability to produce carbohydrate through photosynthesis as their leaves are destroyed.
• Severe acid rain destroys the greenery of a region.
• The acidic nature of water causes the death and distruction of fish and corals.

Question 36.
Calcium oxide reacts with water.
A. What is the product obtained by the reaction?
B. Property of which of the following it has?
(Acid, Alkali, Neutral solution)
Answer:
A. Calcium hydroxide (Ca(OH)₂)
B. Alkali

Question 37.
What are the situations in our day to day life in which neutralisation is made use of?
Answer:
In the agricultural field we use suitable manures according to the crops. The acid-alkaline properties are checked before applying the fertilizer. Similarly the acidic property is neutralised by adding alkaline substances like slaked lime. The acidity in our stomach is removed by treating with antacids. Antacids remove the acidity by neutralisation. In the laboratories in case of burning due to acids, weak alkalies are used as a first aid for its treatment. Here also neutralisation is made use of.

Question 38.
Describe the experiment to identify a carbonate salt.
Answer:
Take a little of the salt solution (e.g., sodium carbonate) in a test tube.
Add a few drops of dilute hydrochloric acid (HCl).
Observation 1: Bubbles (effervescence) will form, indicating a gas is liberated.
Confirmation: Pass this gas through clear lime water Ca(OH)₂ solution) using a delivery tube.
Observation 2: The clear lime water will turn milky. This confirms the gas is Carbon Dioxide (CO₂) and the salt is a carbonate.

Question 39.
Describe the experiment to identify a sulphate salt.
Answer:
Take a little of the salt solution in a test tube.
Add a few drops of barium chloride (BaCl₂) solution.
Observation 1: A white precipitate (Barium Sulphate, BaSO₄ will form.
Confirmation: Add a few drops of di-lute hydrochloric acid (HCl) to the precipitate.
Observation 2: The white precipitate will not dissolve.

Question 40.
The pH of solutions P, Q, Rare given.

Solution	PH
P	4
Q	9
R	7

A. Among them which is the neutral solution?
B. Among them which solution gives CO₂ when reacts with Na₂CO₃? Why?
C. Which solution has more concentration of OH^– ions?
Answer:
A. R
B. Solution P. Because it being an acid reacts with Na₂CO₃ and gives CO₂
C. Q

Question 41.
20mL of NaOH is taken in a conical flask and two drops of phenolphthalein are added. Then dilute HCl is added drop by drop, continuously shaking the beaker.
a) NaOH solution is turned into pink colour when phenolphthalein is added. Which nature of the solution is indicated here?
b) As HCl is added, the intensity of pink colour of solution decreases and finally disappeares. Why? Explain.
c) Write the chemical equation of the reaction that has occured here?
Answer:
a) Basic nature
b) Acidic HCl reacts with basic NaOH to form neutral salt and water. As the concentration of base decreas-es the pink colour fades and finally disappears due to neutralisation reaction.
c) NaOH + HCl → NaCl + H₂O

Question 42.
At the initial stages of cultivation the pH value o the soil is found. What is the need of it?
Answer:
In the case of farming, the pH value of the soil has an important role. A particular pH range is required for the healthy growth of certain crops. Certain crops grow well in the soil that is acidic in nature. But certain other crops grow well in the soil that is basic in nature. In situations like this, soil samples are collected in a suitable manner. The samples are mixed and water is added to get a solution. The pH value of the solution is found out to determine the pH value of the soil.

Question 43.
The pH of a soil is measured during soil testing.
a) Why the pH of soil is measured?
b) Suggest a method to increase the pH of soil with pH = 5.
Answer:
a) The pH of soil is an important factor for crops. It is important to identify whether the soil of a region is suitable for a particular crop. For some crops, soil with acidic nature is suitable and for some other crops, soil with alkaline nature is suitable.

b) Sprinkling of slaked lime.

Question 44.
A student adds a piece of magnesium ribbon to a test tube containing dilute sulphuric acid.
a) What is the main observation?
b) How can the gas produced be identified?
Answer:
a) The student will observe bubbles (effervescence) as the magnesium reacts with the acid,
b) The gas produced is hydrogen (H₂). It can be identified by holding a burning matchstick at the mouth of the test tube. The gas will extinguish the flame with a ‘pop’ sound.

Question 45.
Match the following appropriately.

Common name	Chemical name
a. Caustic soda	i) Magnesium hydroxide
b. Milk of lime	ii) Potassium hydroxide
c. Caustic Potash	iii) Sodium hydroxide
d. Milk of magnesia	iv) Calcium hydroxide

A. a – (ii), b – (i), c – (iii), d – (iv)
B. a – (i), b – (ii), c – (iii), d – (iv)
C. a – (iii), b – (ii), c – (iv), d – (i)
D. a – (iii), b – (iv), c – (ii) d – (i)
Answer:
D. a – (iii), b – (iv) c – (ii) d – (i)

Common name	Chemical name
a. Caustic soda	iii) Sodium hydroxide
b. Milk of lime	iv) Calcium hydroxide
c. Caustic Potash	ii) Potassium hydroxide
d. Milk of magnesia	i) Magnesium hydroxide

Question 46.
Complete the chemical equation for the reaction between magnesium and sulphuric acid.
Mg + H₂SO₄ → ……………. + …………..
Answer:
Mg + H₂SO₄ → MgS0₄ + H₂.

Question 47.
Complete the equation for the reac-tion when Carbon dioxide (CO₂) gas is passed through water. Name the product formed.
CO₂ + H₂O → ……………. + …………..
Answer:
CO₂ + H₂O → H₂CO₃ (Carbonic acid).

Question 48.
Complete the following neutralisation reaction and identify the salt formed.
KOH + HNO₃ → ……………. + …………..
Answer:
KOH + HNO₃ → KNO₃ + H₂O. The salt formed is Potassium Nitrate.

Question 49.
From the chapter, write the chemical formulas for the following acids:
(a) Sulphuric acid
(b) Phosphoric acid
(c) Nitric acid
Answer:
a) H₂SO₄
b) H₃PO₄
c) HNO₃

Question 50.
How many H⁺ (hydrogen) ions and SO₄^2- (sulphate) ions are liberated when 3 molecules of Sulphuric Acid (H₂SO₄) dissolve in water?
Answer:
One molecule of H₂SO₄ liberates 2H⁺ ions and SO₄^2- ion.
Therefore, 3 molecules will liberate:
3 \times 2 = 6H⁺ ions.
3 \times 1 = 3 SO₄^2- ions

Question 51.
Identify the chemical formulas of the acid and base needed to form the salt Aluminium Sulphate (Al₂(SO₄)₃).
Answer:
Acid: Sulphuric acid (H₂SO₄
Base: Aluminium hydroxide (Al(OH)₃)

Question 52.
What is the characteristic effect of an acid on blue litmus paper?
(A) Turns blue
(B) Turns red
(C) No change
(D) Turns yellow
Answer:
(B) Turns red

Question 53.
Which ion is primarily responsible for the general properties of acids in an aqueous solution?
(A) Cl^–
(B) OH^–
(C) H⁺
(D) Na⁺
Answer:
(C) H⁺

Question 54.
Which organic acid is responsible for the sour taste in Tamarind?
(A) Lactic acid
(B) Citric acid
(C) Acetic acid
(D) Tartaric acid
Answer:
(D) Tartaric acid

Question 55.
Which substance is commonly used as an Antacid to reduce excessive stomach acidity?
(A) Hydrochloric acid (HCl)
(B) Magnesium hydroxide (Mg(OH)₂)
(C) Sodium hydroxide (NaOH)
(D) Sulphuric acid (H₂SO₄)
Answer:
(B) Magnesium hydroxide (Mg(OH)₂)

Question 56.
Complete the following chemical reaction which shows an acid reacting with a highly reactive metal.
Zn + 2HCl → ZnCl₂ + ___________
Answer:
Zn + 2HCl → ZnCl₂ + H₂(Hydrogen gas (H₂) is liberated when acids react with highly reactive metals like Zinc.)

Question 57.
Define amphoteric oxides and give one example.
Answer:
Amphoteric oxides are oxides that have both acidic and basic properties. This means they can react with both acids and bases.
Example: Al₂O₃ (Aluminium oxide) or ZnO (Zinc oxide).

Question 58.
Write the balanced chemfcqi equation for the reaction of Sulphur dioxide (SO₂) gas with water (H₂O).
Answer:
SO₂ + H₂O → H₂SO₃ (Sulphurous acid)

Question 59.
What is the pH value of a neutral solution? What characteristics do solutions with a pH value greater than 7 show?
Answer:
The pH value of a neutral solution is 7. Solutions with a pH value greater than 7 show basic characteristics.

Question 60.
Explain what Acid Rain is, and state two negative effects it has on the environment.
Answer:
Acid Rain:
Acid rain is the result of nonmetal oxide gases like SO₂ (Sulphur dioxide) and NO₂ (Nitrogen dioxide) reaching the atmosphere, dissolving in rainwater, and falling to the earth as acids.

Two Environmental Effects:

1. It damages plant leaves, which reduces the ability of plants to produce starch through photosynthesis.
2. It increases the acidity of water sources, which in turn causes the death of aquatic life like fish and coral reefs.

Question 61.
Define Neutralisation Reaction and complete the chemical equation for the reaction between Sodium Hydroxide (NaOH) and Hydrochloric Acid (HCl).
NaOH + HCl → _________ + ______
Answer:
Neutralisation Reaction:
A neutralisation reaction is the chemical reaction in which an acid and a base react and lose their characteristic properties to form water and a salt.
Complete the equation:
NaOH + HCl → NaCl + H₂O
(The products are Sodium Chloride (NaCl), which is the salt, and Water (H₂O).)