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Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 9 Cells and Cell Clusters Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 9 Cells and Cell Clusters Question Answer Notes

Class 8 Basic Science Chapter 9 Notes Kerala Syllabus Cells and Cell Clusters Question Answer

Cells and Cell Clusters Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Identify the word pair relationship and fill the blanks.
a) compound microscope : visible light
……………….. : electron beam
b) Plant cells : eukaryote
………………… : prokaryote
c) Endoplasmic reticulum : Material transport in the cytoplasm
………………….. : Centre for production and distribution of energy
Answer:
a) Electron microscope
b) Bacteria
c) Mitochondria

Question 2.
Choose the statements related to plant cell from the following.
(a) Centrosome is present
(b) Plasma membrane is absent
(c) Plastids are present
(d) Presence of comparatively large vacuoles
Answer:
(c) Plastids are present and (d) Presence of comparatively large vacuoles

Question 3.
Information related to certain cell organelles are given in the table. Complete it by selecting suitable terms from the box.

Answer:
A – f) Golgi apparatus
B – e) Chloroplast
C – d) Ribosome
D – b) Leucoplast

Basic Science Class 8 Chapter 9 Question Answer Kerala Syllabus

Answers to the indicators on page no. 136
Question 1.
Where should the slide be placed in a microscope?
Answer:
The Slide should be placed on the stage of the microscope, and the stage clip is used to keep the slide in place.

Question 2.
Which is the part that regulates the light on the slide?
Answer:
The diaphragm in the condenser controls the amount of light. The condenser lens above this focuses the light onto the object being observed. Mirror- Reflects light from the light source onto the diaphragm.

Question 3.
Which are the lenses used in microscopes?
Answer:
The eyepiece, objective lens, and condenser are the main parts of a microscope that are attached to the lens.

Question 4.
Completed illustration 9.2

Answer:

Question 5.
Completed table 9.1

Answer:

Part of a microsope	Function
Eye piece lens	The image formed by the objective lens is again magnified
Knobes	Used to focus the lenses on the object being observed. The larger knob is called coarse adjustment and the smaller knob is called fine adjustment
Objective lens	The image of the object being observed is magnified and projected into the inner surface of the eyepiece. The part where the objective lenses are mounted is called the nosepiece.
Stage	Used to place slide
Clip	Used to keep the slide in place
Diaphragm in condenser	Control the amount of light
Condenser lens	Helps focus light onto the object.
Mirror	Light from the light source is reflected onto the diaphragm

Question 6.
Completed table 9.2 comparing the peculiarities of different types of microscopes.

Answer:

Peculiarity	Compound microcope	Electron microscope
Need of light	Light is needed	Electron beam is used instead of light
Magnifying power	Up to a thousand times	It magnifies objects more than a million times more than a normal microscope
Lens	Using multiple lenses	Electro magnets are used

Question 7.
Note prepared based on the illustration 9.3 page 140

Answer:
A normal microscope can observe mitochondria, bacteria, red blood cells, yeast, animal cells, plant cells, paramecium, and ova. An electron microscope is an instrument that magnifies objects more than a million times larger than a normal microscope. It helps in the detailed observation of living cells, viruses, and molecular structures. An electron microscope helps in the detailed observation of DNA, viruses, and proteins, which cannot be observed under a normal microscope.

Answers to the indicators on page 141
Question 8.
While preparing the slide:
Answer:

• Use a sharp blade for smooth, thin sections.
• Take the thinnest sections possible. Thin sections allow light to pass through easily.
• Cut straight across to get a proper cross-section.
• Place the thin section on a clean glass slide.
• Add a few drops of water or glycerin to prevent drying.
• Cover with a cover glass using a needle to prevent air bubbles from entering.

Question 9.
Staining:
Answer:

• Use a suitable stain such as safranin or methylene blue.
• Stain for only a few seconds
• Rinse gently with water to remove excess stain before covering with a coverslip.

Question 10.
Observing in high power and low power:
Answer:
Low Power: Observe with a low-power objective lens. Helps to see the epidermis, cortex, pith, etc. Adjust the mirror for a clear view.
High Power: Switch to high power to see things like xylem and phloem. Use the fine adjustment knob to adjust the clarity. Do not move the slide when switching from low power to high power.

Question 11.
Observing and illustrating:
Answer:

• Observe carefully and patiently.
• Draw neatly with a pencil.
• Draw only what you see.
• Use arrows for labelling and write names neatly.

Question 12.
Practical record on page 142 of the textbook:
Answer:
Experiment Name: Plant Stem Observation
Objective: Observe the cells in a plant stem through a microscope.
Materials Required: Microscope, plant stem, Petri dish, glass slide, cover glass, glycerin, blade, tissue paper, needle, brush, water, safranin stain, watch glass.

Procedure:
To prevent dehydration of the object to be observed, place it in Water in a Petri dish. Take thin cross-sections of the object to be observed. Transfer the sections to the water in a watch glass using a brush. Place the thinnest and most complete sections in a diluted stain taken in another watch glass. Add one or two drops of glycerin to prevent the object from drying out. Use a brush to pick up the stained section gently, then wash it in clean water and place it in glycerin on the slide. Cover it with a cover glass using a needle to prevent air bubbles from entering. Wipe off excess glycerin with tissue paper. Observe under a microscope.

Observation:

Conclusion:
Various types of cells are found in plant stems.

Question 13.
Completed illustration 9.5 page 143

Answer:

Question 14.
Completed illustration 9.7 page 147

Answer:

Question 15.
Completed table 9.3 page 149

Answer:

Plant tissues	Characteristics	Functions
Parenchyma	Contain living cells. Thin cell wall. Intercellular spaces are present. Cells in some parts have the ability to divide.	Perform functions such as photosynthesis and food storage.
Collenehyma	A tissue made up of living cells. The cell wall is made of substances such as cellulose and pectin. The cell wall is thicker only in some parts.	Helps in maintaining the shape of plant parts.
Selerenehyma	A tissue consists of dead cells. Thick-cell-wall. The cell wall is of uniform thickness throughout.	Providing strength and support to plant parts.
Xylem	Made up of cells of different shapes and sizes.	Conduction of water and salt to the leaves take place through xylem.
Phloem	Made up of cells of different shapes and sizes.	Carries food synthesised by the leaves to different parts of the plant body.

Question 16.
Completed illustration 9.9 page 151

Answer:

Question 17.
Completed illustration 9.10 page 152

Answer:

Question 18.
Completed table 9.4 page 153

Answer:

Part	Plant cell	Animal cell	Function
Cell wall	present	Absent	Provides protection and shape to the cell
Centrioles	Absent	Present	Helps in cell division
Plastids	Present	Not present	Helps in the production and storage of food.
Lysosome	Absent	Present	Destroying foreign objects

Class 8 Basic Science Chapter 9 Question Answer Extended Activities

Question 1.
Prepare models of Plant cell and Animal cell using materials available in your surroundings.

Question 2.
Prepare a picture chart showing the diversity of cells and exhibit it in the class.
Answer:

Question 3.
Prepare a timeline showing the development of cytology and present it in the class.
Answer:

Cells and Cell Clusters Class 8 Notes

Class 8 Basic Science Cells and Cell Clusters Notes Kerala Syllabus

• Cell biology is the study of cells.
• Human eye can distinguish two spots having a distance of 0.2 mm in adequate light. This distance is called resolution of the eye.
• A simple microscope in which a single lens is used, can magnify an object upto 10 times than the original size, while in a compound microscope, in which more than one lens is used, can magnify an object up to 1000 times.
• Magnification power of a lens is its ability to magnify objects.
• Electron microscope is an instrument that magnifies objects more than a million times. It helps to observe cells, viruses and molecular structure in detail.
• In electron microscope electron beam is used instead of light.
• In 1934 German scientists Ernest Raska and Max Knoll invented electron microscope.
• The various parts of a plant cell are the cell wall, cell membrane or plasma membrane, cytoplasm, and cell organelles.
• Organelles are parts found in the cytoplasm that perform functions necessary for the survival of the cell.
• The organelles in plant cells are nucleus, Golgi apparatus, endoplasmic reticulum, and mitochondria, chloroplast, ribosome, vacuole, etc.
• Plastids are specialized parts of plant cells that help produce and store food. Chloroplast, chromoplast and leucoplasts are different forms of plastids.
• The group of similar type of cells are known as tissues. Tissues that are composed of similar type of cells are known as simple tissues. Xylem and phloem are composed of cells with different shape and size. So they are called complex tissues.
• Meristermatic tissues are composed of cells that are capable of continuous division. Meristematic cells cause growth of plants. Cell clusters or tissues that have lost their ability to divide are known as permanent tissues, Parenchyma, sclerenchyma, collenchyma, xylem arid phloem are examples for permanent tissues.
• Some organelles, such as lysosomes and centrioles, are found in animal cells that are not found in plant cells.
• Tissues composed of group of similar cells perform various functions in the body of animals are called animal tissues. Epithelial tissue, Connective tissue, Muscle tissue, and Neural tissue are different types of animal tissues.
• Stem cells are specialised cells that can develop into various types of cells such as muscle cells, nerve cells, blood cells, etc. Stem cells help to eliminate damaged cells, promote the growth of new cells and maintain healthy tissues.

INTRODUCTION

Imagine looking at your hand, or a leaf from a tree, or even a tiny ant. Have you ever wondered what these living things are made of? Well, just like a building is made of many bricks, all living organisms, from the smallest bacteria to the largest elephant, are made up of tiny basic units called cells.

Cells are often called the “building blocks of life” because they are the smallest units that can perform all the functions necessary for life, like taking in nutrients, growing, and reproducing. They are so tiny that you can’t see them with your naked eye; you need a special instrument called a microscope to observe them.

In this chapter, we’re going to explore the amazing world of cells. We’ll learn about what a cell looks like and its different parts, how different cells come together to form cell clusters (Tissues), Cell theory, and contributions of different scientists in this field.

HISTORY OF CELL BIOLOGY

• Cell biology is the study of cells.
• Matthias Jakob Schleiden discovered that all plants are composed of cells.
• Theodor Schwann discovered that all animals are composed of cells.
• Rudolf Virchow introduced the concept that new cells are formed from pre-existing cells.

Cell Theory

• • All organisms are made up of one or more cells.
  • The cell is the basic unit of life.
  • New cells originate from pre-existing cells.
• Different types of microscopes are used to observe very small or tiny cells. In simple microscopes, lenses are used to magnify objects.
• The human eye can distinguish two spots having a distance of 0.2 mm in adequate light. This distance is called the resolution of the eye.
• A lens is required to distinguish spots having a distance of less than 0.2 mm.
• A simple microscope in which a single lens is used can magnify an object upto 10 times than its original size.
• A compound microscope, in which more than one lens is used, can magnify an object up to 1000 times.
• The magnification power of a lens is its ability to magnify objects. If eye piece lens magnifies the object to 10 x (10 times) and objective lens magnifies it into 40 x (40 times), the magnification power of the lens is 400 x.

Electron microscope

• An instrument that magnifies objects more than a million times.
• It helps to observe cells, viruses and molecular structure in detail.
• In an electron microscope electron beam is used instead of light.
• In 1934, German scientists Ernest Raska and Max Knoll invented the electron microscope.
• In an electron microscope, electromagnetic lenses are used to focus a beam of electrons onto the specimen, allowing for much higher resolution imaging compared to light microscopes.

LET’S OBSERVE CELLS

• Living organisms have cells of different shapes and sizes in their bodies.
• The basic structure of all the different cells in a leaf and a stem is the same.

• Cell Wall – The cell wall is the rigid outer layer of the cell membrane.
• The cell membrane, or plasma membrane – Thin, flexible layer that surrounds the cell. Substances enter and leave the cell through the cell membrane.
• The plasma membrane does not allow all substances to pass through. Therefore, the plasma membrane is known as the semi-permeable membrane.
• Protoplasm – It consists of all the components inside the cell membrane, including the nucleus and cytoplasm.
• Cytoplasm – A jelly-like fluid that fills the cell. It maintains all the organelles in their place and serves as the medium for chemical reactions.
• Organelles are the parts found in the cytoplasm and perform the functions necessary for the survival of the cell.
• The organelles of a plant cell are the cytoplasm, Golgi apparatus, endoplasmic reticulum, and mitochondria.
• Nucleus – The centre that controls the cell. The chromatin network is the structure that appears like a network of threads within the nucleoplasm. During cell division, these chromatin networks condense into chromosomes.
• Golgi Apparatus – Cell organelles that appear as stacked membrane layers. These organelles transport proteins and lipids to various parts of the cell and outside the cell, wrapped in membranous sacs.
• Endoplasmic Reticulum – Organelles appear as a network of tubules within the cell, and serve as pathways for conducting materials. It helps in the synthesis and removal of materials required by the cell.
• Mitochondria – The energy production centre of the cell.
• Plastids – Specific parts in the plant cells that help in the synthesis and storage of food materials. They have a two-layered membrane. Different types of plastids perform different functions.

• Vacuole – Stores water, nutrients and wastes. Usually, large vacuoles are seen in plant cells.
• Ribosome – Found in the cytoplasm either freely or attached to the endoplasmic reticulum. They function as the centre for protein synthesis.

TISSUES
PLANT TISSUES

• The group of similar type of cells are known as tissues.

• Tissues that are composed of similar types of cells are known as simple tissues.
• Xylem and phloem are composed of cells with different shapes and sizes. So they are called complex tissues.
• The transport of water and salts to the leaves takes place through the xylem.
• The food produced by the leaves is transported to various parts by the phloem tissue.
• Meristematic tissues are composed of cells that are capable of continuous division. Meristematic cells are responsible for the growth of plants.

• Cell clusters or tissues that have lost their ability to divide are known as permanent tissues. Parenchyma, sclerenchyma. Collenchyma, xylem and phloem are examples of permanent tissues.

ANIMAL TISSUES

• The animal body is also made up of different types of cells (Animal tissues).
• Some organelles, such as lysosomes and centrioles, are found in animal cells that are not found in plant cells.

Stem cells are specialised cells that can develop into various types of cells, such as muscle cells, nerve cells, blood cells, etc.

• Stem cells help to eliminate damaged cells, promote the growth of new cells and maintain healthy tissues.
• In modern medicine, stem cells have great significance.
• Despite these differences, there are many similarities among living organisms.
• These common characteristics of living things lead us to the reality that the basis of life is one and the same.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 5 Elements and Compounds Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 5 Elements and Compounds Question Answer Notes

Class 8 Basic Science Chapter 5 Notes Kerala Syllabus Elements and Compounds Question Answer

Elements and Compounds Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Match the following

A Element	B Symbol	C Base
Francium	Rb	continent
Curium	Eu	satellite
Rubidium	Ti	colour
Neptunium	Cm	country
Europium	Fr	planet
Titanium	Np	scientist

Answer:

A Element	B Symbol	C Base
Francium	Fr	Country
Curium	Cm	Scientist
Rubidium	Rb	Colour
Neptunium	Np	Planet
Europium	Eu	Continent
Titanium	Ti	Satellite

Question 2.
Cl is the symbol of the element chlorine. How can we represent two chlorine atoms and one chlorine molecule using this symbol?
Answer:

• Two chlorine atoms – 2 Cl
• One chlorine molecule – Cl₂

Question 3.
Find the number of atoms in each of the following and write which of them contains the most number of atoms.
5NH₃, 2H₂O, 5NO₂, 4CO₂

Element	Number of Atoms
5NH3	5 N + (5 × 3) H = 5 N + 15 H = 20
2H2O	(2 × 2)H + 2 O = 4H + 2 O = 6
5NO2	5 N + (5 × 2) O = 5 N + 10 O = 15
4CO2	4C + (4 × 2) O = 4C + 8 O = 12

Ammonia contains the most number of atoms.

Question 4.
Complete the table.

Answer:

Element	Basis of nomenclature	Symbol
Indium	Indigo – colour	In
Rutherfordium	Rutherford – Scientist	Rf
Germanium	Germany – Country	Ge
Silver	Argentum – Latin name	Ag

Question 5.
The names of some scientists are given.
(Dobereiner, Lavoisier, Newlands, Mendeleev)
Match the statements given below with the names given in brackets
i. The chemical and physical properties of the elements are functions of their atomic masses.
ii. Elements were divided into groups containing three elements (triads) with similar properties.
iii. The elements were classified into metals and non-metals.
iv. When the elements were arranged in ascending order of atomic masses, it was found that every eighth element was a repetition of the first, in terms of its properties.
Answer:
i. Mendeleev
ii. Dobereiner
iii. Lavoisier
iv. Newlands

Basic Science Class 8 Chapter 5 Question Answer Kerala Syllabus

Question 1.
What do you know about molecules? Try to write it.
Answer:
Molecules are tiny particles made of two or more atoms stuck together by invisible bonds, forming the basic building blocks of all matter.

Question 2.
Can you formulate a definition for molecules?
Answer:
Molecules are the smallest, independent and stable particles that have all the fundamental properties of a pure substance.
New molecules are formed through chemical reactions.

Question 3.
Let’s do an experiment.
a) Burn a magnesium ribbon which is scrubbed clean. Record your observations.
Answer:
Observation: Magnesium burns brightly in air. A white powder is obtained.

b) What is the white powder obtained as a result of the reaction?
Answer:
It is magnesium oxide, produced when magnesium reacts with oxygen.
This is an example of the formation of new molecules through chemical reactions between different types of molecules.
We can dissociate molecules to make new molecules.

Question 4.
Take some sugar in a dry boiling tube. Cover the mouth of the boiling tube with a piece of cotton. Heat the boiling tube strongly for a few minutes. Write your observations.
Observation – A black substance remains in the boiling tube.

a) What is the black substance left in the boiling tube?
Answer:
Carbon

b) What is the substance seen on the sides of the boiling tube?
Answer:
Water

We can observe that when sugar is heated, carbon and water are formed. Sugar molecules can be broken down through chemical reactions.

Question 5.
Let’s do another experiment.
Take some dilute hydrochloric acid in a test tube and add a small piece of magnesium to it. Introduce a burning incense stick to the mouth of the test tube. Record your observations.
Observation – A vigorous chemical reaction takes place. A gas is released. When the incense stick is introduced to the mouth of the test tube, the gas burns with a pop sound.

a) What is the gas produced as a result of the reaction?
Answer:
Hydrogen (H₂)

b) How can we represent this reaction?
Answer:
Magnesium + Hydrochloric Acid → Magnesium Chloride + Hydrogen

Question 6.
Collect the hydrogen gas obtained in this experiment into another moisture-free test tube and introduce a burning incense stick to it. Record your observations.
Answer:
The gas burns with a popping sound. Water droplets are visible on the sides of the test tube.

а) What do you understand from the presence of water droplets on the sides of the test tube?
Answer:
Hydrogen in the test tube reacts with oxygen to form water.
Hydrogen + Oxygen → Water

Henry Cavendish proved that water is a substance made up of more than one element. His experiment of burning hydrogen gas in the presence of oxygen helped to know about the components of water.

In 1806, Sir Humphry Davy discovered that water could be split into hydrogen and oxygen by passing electricity through it.

Question 7.
Which are the substances obtained when water is dissociated?
Answer:
Hydrogen and Oxygen

Question 8.
Can hydrogen and oxygen be further split in to components?
Answer:
No

Question 9.
Look at the table below

Molecules	Atoms in a molecule
Ammonia	One atom of nitrogen Three atoms of hydrogen
Oxygen	Two atoms of oxygen
Chlorine	Two atoms of chlorine
Methane	One atom of carbon Four atoms of hydrogen
Hydrogen	Two atoms of hydrogen
Carbon dioxide	One atom of carbon Two atoms of oxygen

a) Which molecules in the table consist of the same type of atoms?
Answer:
Oxygen, Chlorine, Hydrogen

b) Which of these molecules consist of different types of atoms?
Answer:
Ammonia, Methane, Carbon dioxide

• Elements are pure substances made up of the same type of atoms. They cannot be further divided into components through chemical reactions.
• Compounds are pure substances formed by the combination of atoms of two or more elements in a fixed ratio. These can be dissociated into constituent elements through chemical reactions.

Question 10.
Categorise the following into elements and compounds.
Oxygen, water, salt, sugar, carbon, nitrogen, carbon dioxide, ammonia, magnesium oxide

Answer:

Elements	Compounds
• Oxygen • Carbon • Nitrogen	• Water • Salt • Sugar • Carbon dioxide • Ammonia • Magnesium oxide

Question 11.
Note the list of other elements represented by the first letter of their name. Expand the list by adding more elements.

Answer:

Element	Symbol
Carbon	C
Nitrogen	N
Sulphur	S
Oxygen	O
Boron	B
Phosphorus	P
Fluorine	F
Iodine	I
Vanadium	V
Yttrium	Y
Uranium	U

Question 12.
The element Helium is represented by the symbol ‘He’. The first and second letters of the English name are used here. What could be the reason?
Answer:
H is the symbol for hydrogen. More than one element may have the same first letter.

• Some elements are represented by another, letter along with the first letter of the English name in upper case. See more examples of using two letters as symbols.

Element	Symbol
Aluminium	Al
Chlorine	Cl
Curium	Cm
Calcium	Ca

• The first letter of the English name is used upper ease along with the second letter or any other prominent letter in lower case.

Question 13.
Find more examples and expand the list.
Answer:

Element	Symbol
Germanium	Ge
Neon	Ne
Manganese	Mn
Cobalt	Co
Zinc	Zn
Beryllium	Be
Magnesium	Mg
Barium	Ba
Radium	Ra
Silicon	Si

Some elements have symbols based on their Latin names.

Question 14.
Find more examples and expand the list.

Answer:

Element	Latin name	Symbol
Sodium	Natrium	Na
Potassium	Kalium	K
Iron	Ferrum	Fe
Gold	Aurum	Au
Copper	Cuprum	Cu
Silver	Argentum	Ag
Tin	Stannum	Sn
Lead	Plumbum	Pb
Antimony	Stibium	Sb
Mercury	Hydrargyrum	Hg
Element	Latin name	Symbol

• The symbol “W” is derived from the German name ‘Wolfram’ for the metal tungsten.

Question 15.
Find put how the elements given below got their names.
• Chromium
• Iridium
• Neptunium
Answer:
• Chromium – From the world “chroma,” meaning colour.
• Iridium – From the word “Iris,” meaning Rainbow.
• Neptunium – From the name of the planet “Neptune”.

Question 16.
Analyse the Periodic Table and write down the name and symbol of any 5 elements.
Answer:

• Lithium (Li)
• Sodium (Na)
• Beryllium (Be)
• Magnesium (Mg)
• Calcium (Ca)

Question 17.
Find out which elements were added last to the periodic table.
Answer:

• Nihonium (Nh)
• Flerovium (Fl)
• Livermorium (Lv)
• Tennessine (Ts)
• Oganesson (Og)

Question 18.
List the elements existing in solid, liquid and gaseous state with the help of periodic table.

Answer:

Solid	Liquid	Gas
Lithium	Caesium	Hydrogen
Sodium	Francium	Nitrogen
Potassium	Mercury	Oxygen
Rubidium	Gallium	Fluorine
Beryllium	Bromine	Chlorine
Magnesium		Helium
Calcium		Neon
Strontium		Argon
Barium		Krypton
Radium		Xenon
		Radon

Question 19.
Find the synthetic elements with the help of the periodic Table.

• Technetium
• Dubnium
• Bohrium
• Meitnerium
• Roentgenium
• Nihonium
• Moscovium
• Tennessine
• Promethium
• Plutonium
• Curium
• Californium
• Fermium
• Nobelium
• Rutherfordium
• Seaborgium
• Hassium
• Darmstadtium
• Copemicium
• Flerovium
• Livermorium
• Oganesson
• Neptunium
• Americium
• Berkelium
• Einsteinium
• Mendelevium
• Lawrencium

Question 20.
Is there any difference between 2N and N₂?
Answer:
2N refers to two free nitrogen atoms. N₂ refers to a nitrogen molecule formed by two nitrogen atoms bonded together.

• 2N – refers to two free nitrogen atoms.
• N₂ – refers to a nitrogen molecule formed by two atoms.
• 2N₂ – refers to two nitrogen molecules.

Question 21.
What is the total number of atoms in 2N₂?
Answer:
2N₂ refers to two nitrogen molecules (N₂ + N₂)
2 atoms in a nitrogen molecule.
Total number of atoms in 2N₂ = 2 + 2 = 4

Question 22.
Check the abbreviation of the molecules of some elements.

Answer:

Molecule	Number of atoms	Category
He	1	Monoatomic elements.
O2	2	Diatomic elements.
S8	8	Polyatomic elements.
H2	2	Diatomic elements
P4	4	Polyatomic elements
Ne	1	Monoatomic element
Cl2	2	Diatomic elements
Ar	1	Monoatomic element
O3	3	Triatomic element

Question 23.
Is it clear that, monoatomic elements are elements that have only one atom in a molecule? Write the difference between diatomic elements and polyatomic elements.
Answer:
Diatomic elements are elements that have two atoms in a molecule. Elements that have more than three atoms in a molecule are called polyatomic elements.

Chemical formula of the molecule represent one molecule of a substance.

Question 24.
Find the number of molecules and the total number of atoms in the following.

Answer:

Substance	No. of molecules	No. of atoms
H2	1	1 × 2 = 2
5O2	5	5 × 2 = 10
6N2	6	6 × 2 = 12
4Cl2	4	4 × 2 = 8
8	1	1 × 8 = 8

Question 25.
Write the symbols for hydrogen and chlorine.
Answer:
Hydrogen – H
Chlorine – Cl
A molecule of hydrogen chloride contains one hydrogen atom and one chlorine atom.
We represent a molecule of hydrogen chloride as HCl.

Question 26.
How can we represent a molecule of water in the same way?
Answer:
H₂O

Question 27.
Complete the table.

Answer:

A compound has a certain ratio between the number of atoms of its constituent elements.
Example: HCl =1 : 1
H₂O = 2 : 1
NH₃ = 1 : 3
CO₂ = 1 : 2

Question 28.
Find the number of molecules and the total number of atoms present in 3CO₂.
Answer:
Number of molecules = 3
Atoms C = 3 × 1 = 3
0 = 3 × 2 = 6
Total number of atoms = 9

Question 29.
Complete the table given below.

Answer:

Compound	No. of molecules	No. of atoms
2HCl	2	H – 2 × 1 = 2 Cl – 2 × 1 = 2 4
4SO2	4	S – 4 × 1 = 4 0 – 4 × 2 = 8 12
3C2H5OH	3	C – 3 × 2 = 6 H – 3 × 6 = 18 0 – 3 × 1 = 3 27
2C6H12O6	2	C – 2 × 6 = 12 H – 2 × 12 = 24 O – 2 × 6 = 12 48

Question 30.
What are the reactants in this reaction?
Answer:
Carbon, Oxygen

Question 31.
What are the products?
Answer:
Carbon Dioxide

Question 32.
How do you write the reactants using chemical formula?
Answer:
C, O₂

Question 33.
How about products?
Answer:
CO₂
This chemical reaction can be represented as C + O₂ → CO₂

A chemical equation is the representation of a chemical reaction which helps to understand it at a glance. It uses symbols/chemical formulae to represent the reactants and products.

Question 34.
Calcium carbonate (CaCO₃) decomposes to form calcium oxide (CaO) and carbon dioxide (CO₂). How can this chemical reaction be represented?
Answer:
CaCO₃ → CaO + CO₂

Question 35.
Write the chemical equations of some chemical reactions that you are familiar with.
Answer:

• 2H₂ + O₂ → 2H₂O
• H₂ + Cl₂ → 2HCl
• 2Mg + O₂ → 2MgO
• CaO + H₂O → Ca(OH)₂
• Mg + 2HCl → MgCl₂ + H₂

Class 8 Basic Science Chapter 5 Question Answer Extended Activities

Question 1.
Make models of the molecules using materials available in your surroundings.
• Carbon tetrachloride (CCl₄)
• Ammonia (NH₃)
• Water (H₂O)
Answer:
Here are short instructions for making the molecule models:

General Materials:

• Atoms: Different coloured clay/Play-Dough/thermocol balls (e.g., Black/Grey for C, Green for Cl, Blue
  for N, White for H, Red for O).
• Bonds: Toothpicks or short stick pieces.

1. Carbon Tetrachloride (CCl₄)

• Atoms: 1 Carbon (large, black/grey), 4 Chlorine (smaller, green).
• Instructions: Connect the central Carbon ball to four Chlorine balls using toothpicks, spreading them out to form the shape of carbon tetrachloride.

2. Ammonia (NH₃)

• Atoms: 1 Nitrogen (medium, blue), 3 Hydrogen (small, white).
• Instructions: Connect the central Nitrogen ball to three Hydrogen balls using toothpicks. Arrange the Hydrogen atoms to form the base of a pyramid with Nitrogen at the top.

3. Water (H₂O)

• Atoms: 1 Oxygen (medium, red), 2 Hydrogen (small, white).
• Instructions: Connect the central Oxygen ball to two Hydrogen balls using toothpicks. Angle the Hydrogen atoms to create a V-shaped molecule.

Question 2.
Prepare a slide presentation/chart on the history of development of Periodic Table and exhibit it in the classroom.
Answer:
The Periodic Table: A Journey of Discovery
(Slide 1 / Chart Title)
Slide 2 / Section 1: Early Groupings (1800s)

• Dobereiner’s Triads (1829): Grouped elements in threes with similar properties.
• Newlands Law of Octaves (1865): Noted repeating properties every eighth element when arranged by atomic weight.

Slide 3 / Section 2: Mendeleev’s Breakthrough (1869) ‘

• Dmitri Mendeleev: Arranged elements by increasing atomic weight.
• Key Insight: Left gaps for undiscovered elements and predicted their properties.
• Significance: His predictions were later proven correct, validating his table.

Slide 4 / Section 3: Moseley’s Refinement (1913)

• Henry Moseley: Discovered that elements are best arranged by increasing atomic number (number of protons).
• Impact: Fixed drawbacks in Mendeleev’s table, leading to the modern version.

Slide 5 / Section 4: The Modem Periodic Table

• Basis: Organised by increasing atomic number.
• Structure: Elements with similar properties fall into the same groups (columns).
• Importance: Essential tool for understanding chemistry and predicting element behaviour.

Elements and Compounds Class 8 Notes

Class 8 Basic Science Elements and Compounds Notes Kerala Syllabus

• When sugar is heated, carbon and water are formed. Sugar molecules can be broken down through chemical reactions.
• Molecules are the smallest particles obtained by dissociating various substances having their fundamental properties.
• Atoms are obtained when molecules are split.
• Dalton’s Atomic theory
  • All matter is made up of minute particles called atoms.
  • An atom is the smallest particle that can participate in a chemical reaction.
  • An atom cannot be divided during a chemical reaction.
  • An atom cannot be created or destroyed.
  • All atoms of an element are of the same size, property and mass.
  • Atoms of different elements differ in their size, property and mass.
• Elements are pure substances made up of the same type of atoms. They cannot be further divided into components through chemical reactions.
• Compounds are pine substances formed by the combination of atoms of two or more elements in a fixed ratio. These can be dissociated into constituent elements through chemical reactions.
• A symbol represents an atom of an element.
• The modern symbol system of representing elements by letters was introduced by a scientist named Berzelius.
• The element hydrogen is represented by the letter ‘H’. That is, the first letter of name of the element is used here as the symbol.
• Some elements are represented by another, letter along with the first letter of the English name in upper case.
• The first letter of the English name is used upper case along with the second letter or any other prominent
  letter in lower case.
• Some elements have symbols based on their Latin names.
• Elements are named on the basis of country, scientists, colour, name of planets, satellites, continents, etc. Example: Francium (Country – France)
  Einsteinum (Scientist – Albert Einstein)
• Lavoisier made the earliest attempts to classify elements. He classified the then-known elements into metals and non-metals.
• Dobereiner classified the elements of similar properties into groups of three. These groups were called triads. He stated that the atomic mass of the element in the middle of the triads was approximately the average of the atomic masses of the other two elements. Only a few elements could be classified in this way.
• Newlands found that when elements were arranged in ascending order of atomic mass, each eighth element was a repetition of the first in its properties. He compared this to the seven notes in music. This classification was known as the Law of Octaves.
• A scientist named Mendeleev arranged the 63 elements known till that day in ascending order of their atomic masses and prepared a table. It was found that elements with common properties were repeated at regular intervals.
• Mendeleev’s periodic law: The physical and chemical properties of elements are the periodic functions of their atomic mass.
• The horizontal rows in the table are called periods and the vertical columns are called groups. Elements in a group show similar chemical properties.
• Advantages of Mendeleev’s periodic table:
  • Elements were arranged in the ascending order of atomic mass.
  • Blank spaces were left for elements to be discovered and their properties were predicted.
  • Elements with similar properties were grouped together to simplify the study of elements and their compounds.
• • Limitations of Mendeleev’s periodic table
  • The order of atomic mass was not strictly followed in the case of all elements. Hydrogen could not be given an exact position.
  • Elements with very different properties had to be placed in the same group.
• Henry Moseley later discovered that the properties of elements depend on their atomic number. The periodic table developed by him is the modern periodic table used today.
• Chemical formula of the molecule represent one molecule of a substance.
• Atomicity is the number of atoms in a molecule.
• In diatomic and polyatomic elements, the atomicity is written as a subscript on the right of the symbol to obtain their chemical formula.
• The total number of molecules is written on the left side of the chemical formula.
• A chemical equation is the representation of a chemical reaction which helps to understand it at a glance. It uses symbols/chemical formulae to represent the reactants and products.

INTRODUCTION

All the objects we see around us are made up of different molecules. Atoms are the smallest particles that are obtained by dividing molecules. Elements are pure substances that contain the same type of atoms. 118 Elements have been discovered so far. Compounds are formed when atoms of elements combine with each other. In the language of chemistry, symbols are used to represent elements, and chemical formulas are used to represent compounds. The periodic table, which has been prepared by classifying the elements comprehensively, makes the study of compounds and elements easier. In this unit, we will learn about the origins of element names, their symbols, chemical formulas of molecules, and the history of element classification.

We know that all objects around us are made up of different molecules. Let us examine how each of these molecules differ with respect to their structural characteristics.

ATOM

• Molecules are the smallest particles obtained by dissociating various substances having their fundamental, properties.
• Atoms are obtained when molecules are split.
• The molecules of every substance are made up of minute atoms. All substances in the universe are made up of atoms. The word “atom” comes from the Greek word “atomos,” which means indivisible.
• Democritus proposed that all matter is made up of indivisible particles called atoms.
  In 1807, John Dalton proposed the atomic theory to explain the nature of atom. Dalton’s Atomic Theory is one of the important theories in modem chemistry. The ideas put forward by Dalton are given below.
  • All matter is made up of minute particles called atoms.
  • An atom is the smallest particle that can participate in a chemical reaction. .
  • An atom cannot be divided during a chemical reaction.
  • An atom cannot be created or destroyed.
  • All atoms of an element are of the same size, property and mass.
  • Atoms of different elements differ in their size, property and mass.

A water molecule is made up of two atoms of hydrogen and one atom of oxygen.

SYMBOLS

• Symbols are used to represent concepts in a clear and simple manner. Symbols make communication and interpretation easier.
• Similarly, signs are used to represent elements. These are known as chemical symbols. A symbol represents an atom of an element.
• The modern symbol system of representing elements by letters was introduced by a scientist named Berzelius.

A symbol represents an atom of an element.

ORIGIN OF SYMBOLS
• The element hydrogen is represented by the letter ‘H’. That is, the first letter of name of the element is used here as the symbol.

HOW ELEMENTS GOT THEIR NAMES
Elements are named on the basis of country, scientists, colour, name of planets, satellites, continents, etc.
Example: Francium (Country – France)
Einsteinum (Scientist – Albert Einstein)

CLASSIFICATION OF ELEMENTS
In a library we can see that books are arranged by categorising them into essays, poems, stories, novels, etc, Elements are also classified in this manner. So far, 118 elements have been discovered which include natural and synthetic elements. It is very difficult to study all these elements and their compounds separately. It would be easier if elements with similar properties are classified into groups.

• The Periodic Table is a table in which all the elements are categorised and arranged based on their properties.

EARLIER ATTEMPTS FOR THE CLASSIFICATION OF ELEMENTS
The modern Periodic Table that we use today is the result of the efforts of many scientists.

• Lavoisier made the earliest attempts to classify elements. He classified the then-known elements into metals and non-metals.
• Dobereiner classified the elements of similar properties into groups of three. These groups were called triads. He stated that the atomic mass of the element in the middle of the triads was approximately the average of the atomic masses of the other two elements. Only a few elements could be classified in this way.

Element	Atomic mass
Li	7
Na	23
K	39
Ca	40
Sr	87.6
Ba	137.3
Cl	35.5
Br	80
I	127

• Newlands found that when elements were arranged in ascending order of atomie mass, each eighth element was a repetition of the first in its properties. He compared this to the seven notes in music. This classification was known as the Law of Octaves. As more elements were discovered, it became clear that all elements could not be arranged in this way.

Li	Be	B	C	N	O	F
Na	Mg	Al	Si	P	S	Cl

• A scientist named Mendeleev arranged the 63 elements known till that day in ascending order of their atomic masses and prepared a table. It was found that elements with common properties were repeated at regular intervals.

The physical and chemifcal properties of elements are the periodic functions of their atomic mass.

MENDELEEV’S PERIODIC LAW
Mendeleev’s Periodic Table is shown in the figure. The horizontal rows in the table are called periods and the vertical columns are called groups. Elements in a group show similar chemical properties.

CHARACTERISTICS

• Elements were arranged in the ascending order of atomic mass. Blank spaces were left for elements to be discovered and their properties were predicted.
• Elements with similar properties were grouped together to simplify the study of elements and their compounds.
• However, the order of atomic mass was not strictly followed in the case of all elements. Hydrogen could not be given an exact position.
• Elements with very different properties had to be placed in the same group.

When Mendeleev’s Periodic Table was formed in 1869, there was limited knowledge about the structure of the atom and its elementary particles. Henry Moseley later discovered that the properties of elements depend on their atomic number. The periodic table developed by him is the modern periodic table used today.

CHEMICAL FORMULA
CHEMICAL FORMULA OF MOLECULES
We use symbols to identify elements easily. If we write N, it refers to nitrogen and one atom of nitrogen.

CHEMICAL FORMULA OF ELEMENTS

• In monoatomic elements, the symbol itself is considered as the chemical formula.
• In monoatomic molecules, the number written on the left of the symbol indicates, the number of molecules. This is also the number of atoms.

Example: 2He → 2 Helium atoms / 2 Helium molecules
3Ne → 3 Neon atoms / 3 Neon molecules
Atomicity is the number of atoms in a molecule. In diatomic Mid polyatomic elements, the atomicity is written as a subscript on the right of the symbol to obtain their chemical formula. The total number of molecules is written on the left side of the chemical formula.
We can find the number of molecules and the number of atoms from the chemical formula of the elements.
3O₂ → 3 oxygen molecules .
Total number of atoms = 3 × 2 = 6 oxygen atoms
5Cl₂ → 5 chlorine molecules
Total number of atoms = 5 × 2 = 10 chlorine atoms

CHEMICAL FORMULA OF COMPOUNDS
Hydrogen and Chlorine are the constituent elements in hydrogen chloride.

CHEMICAL EQUATIONS
Carbon reacts with oxygen to form carbon dioxide.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 6 Metals and Non Metals Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 6 Metals and Non Metals Question Answer Notes

Class 8 Basic Science Chapter 1 Notes Kerala Syllabus Metals and Non Metals Question Answer

Metals and Non Metals Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Match the following.

Answer:

A	B	C
Name of the metal	Characteristic property	Symbol
Silver	High electrical conductivity	Ag
Platinum	High ductility	Pt
Gold	The highest malleability	Au

Question 2.
The names of certain metals are given in the box.

Choose the appropriate metal for the following situations.
a. Reacts with the components of air and forms tarnish on the surface.
b. It is the best conductor of heat.
c. The metal that melts when placed on the palm.
d. It exists in the liquid state in normal temperature.
e. This metal is present in bones and teeth.
Answer:
a. Copper
b. Silver
c. Gallium
d. Mercury
e. Calcium

Question 3.
Certain metals are given in the following table. Find any two uses of each and the characteristic property responsible for it.

Answer:

Metal	Use	Characteristic property
Copper	Manufacture of electric wire	Electrical conductivity, Ductility
	Manufacture of utensils, Idols	Malleability
Gold	Manufacture of ornaments	Malleability, Ductility
	Manufacture of coins	Metallic lustre, Malleability
Aluminium	Manufacture of utensils for cooking	Thermal conductivity, Malleability
	Manufacture of electrical wires	Electrical conductivity, Ductility
Iron	Manufacture of wires, tools etc.	Hardness
	Used for the manufacture of sheets.	Malleability
Silver	Used for the manufacture of ornaments	Malleability, Ductility, Metallic lustre
	Used for the manufacture of coins, idols, etc.	Metallic lustre, Malleability

Question 4.
Oxides of elements A and B are dissolved in water in two separate beakers.
a) How can you identify the acidic solution and the basic solution?
b) Which of these elements is more likely to be a metal? Why?
Answer:
a) Dip red and blue litmus papers in both solutions.

• The solution which turns blue litmus red is the acidic solution.
• The solution which turns red litmus blue is the basic solution.

b) The solution that turns red litmus into blue is formed by a metal oxide, because metal oxides are basic in nature.
Therefore, the element whose oxide formed the basic solution is more likely to be a metal.

Basic Science Class 8 Chapter 6 Question Answer Kerala Syllabus

Question 1.
You must be familiar with different kitchen utensils. What are the common materials used to make utensils for cooking?
Answer:
Aluminium, Copper, Steel, Iron

Question 2.
Let’s do an activity.
Take some water into a flat bowl. Place a wooden ladle and a steel ladle in it and let it boil. Touch the ladles and find out which one is hotter. Why is it so?
Answer:
A steel ladle heats up more because steel conducts heat.

Question 3.
Why are you warned against handling iron-like objects during thunder and lightning?
Answer:
Metals like iron are good conductors of electricity. Therefore, they are susceptible to lightning strikes.

Question 4.
Find out the characteristics of metals as indicated in the above situations.
Answer:
Thermal conductivity
Electrical conductivity

Question 5.
Complete the table below.

Answer:

Question 6.
What are the other characteristics of metals familiar to you?
Answer:

• Very Hard
• High melting point
• High Boiling point
• High Density

Question 7.
Define metals?
Answer:
Metals are substances that exhibit high thermal and electrical conductivity and possess lustre and hardness.

MALLEABILITY

Have a look at the picture.

Question 8.
What is the blacksmith doing?
Answer:
A hammer strikes the piece of metal.

Question 9.
What changes occur when a piece of metal is hammer blown?
Answer:
The piece of metal flattens into a sheet.

Question 10.
Haven’t you seen aluminium foil which is used to wrap tablets and food materials? Which characteristic property of metals is used in this case?

Malleability

Generally, metals can be hammered and flattened into thin sheets. This characteristic property of metals is known as malleability.

• All metals are not malleable to the same extent.
• Gold is the most malleable metal.

Question 11.
Write examples for utilising the malleability of metals.
Answer:

• Metal sheets are used to make roofing of buildings.
• Used for making thin foils. Aluminium foil for packaging food.
• Used for jewellery making.
• Metal sheets are used to make cupboards and furniture.

DUCTILITY

Question 12.
What metal is the filament of the bulb in the picture made of?
Answer:
Tungsten

Question 13.
Can you explain why tungsten is used to make the filament?
Answer:
Tungsten can be drawn into very thin wires.

Question 14.
Define Ductility
Answer:
Metals can be drawn into thin wires. This property of metals is known as ductility.

Metals like gold and copper can be drawn into very fine wires. Gold and Platinum are the most ductile metals.

Question 15.
There are a lot of situations where ductility of metals is utilized. List a few of them.
Answer:

• Electric wires
• Filaments in light bulbs
• Musical instrument strings
• Jewellery
• Construction wires

Question 16.
Which among these objects made the bulb glow?
Answer:
A piece of razor blade, A fine iron wire, aluminium wire, Copper wire,

Question 17.
Are they metals or non-metals?
Answer:
They are metals
The ability of a material to conduct electricity through it is known as electrical conductivity. All metals are electrical conductors.
Silver is the best electrical conductor among the metals. The electrical conductivity of the metals such as silver, copper, gold, and aluminium decreases in the following order.
Silver > Copper > Gold > Aluminium

Question 18.
Which metal is used in household electrical wiring?
Answer:
Copper

Question 19.
Which metal is used to make electric lines for the public distribution of electricity?
Answer:
Aluminium

Question 20.
Why is silver not used for this purpose?
Answer:
High Cost
Low availability

Question 21.
Utensils for cooking are usually made of metal. Which characteristic properties of metals are utilised in this case?
Answer:
Thermal conductivity
Malleability

Question 22.
Define thermal conductivity.
Answer:
The ability of metals to conduct heat is called thermal conductivity. It is one of the fundamental characteristics of metals.

Silver is the best conductor of heat among metals. Metals such as aluminium and copper have relatively high thermal conductivity.

Question 23.
Aluminium is extensively used for cooking utensils. Find the reasons.
Answer:

• High Thermal Conductivity
• Malleability
• More availability
• Low cost

The non-metal carbon exists in two main allotro ic forms, diamond and graphite

Diamond	Graphite
High thermal conductivity	High electrical conductivity
It is used to cut glass	It is used as electrode

The strikingly different properties of diamond and graphite are due to the differences in the carbon
carbon bonding in them.

Question 24.
Give examples of situations where sonority is useful.
Answer:

• Bells, church bells
• Gongs of bells
• Musical Instruments

Question 25.
Identify the situations in which metallic lustre is made use of?
Answer:

• For making ornaments.
• Mirrors and Reflectors.
• Utensils and Cookware.

Question 26.
Is it possible to cut metals such as copper, aluminium and gold in the same manner?
Answer:
No. Lithium, sodium and potassium are soft metals. But other metals are harder.

Question 27.
Give an example of a hard metal.
Answer:
Iron, Copper, Aluminium, Gold

Question 28.
Give an example of soft metals.
Answer:
Lithium, Sodium, Potassium

Question 29.
Are there metals that exist in a liquid state?
Answer:
Yes

Question 30.
Write the names of metals that exist in a liquid state.
Answer:
Mercury (Hg)
Gallium (Ga)
Caesium (Cs)

• Metals generally have high melting points
  However, gallium and caesium are metals that have low melting points. They start melting when placed on our palm. In other words, they exist in the liquid state on warmer days.
• Metals generally have high boiling points.
• Metals generally have high density.

Question 31.
Take some articles made up of different metals (iron nail, aluminium wire), a small piece of wood, charcoal, thermocol and cork. Put each of them one by one in water in a beaker. Which among these articles sink into the water? Which of these floats over water?
Answer:
Articles sink into the water: An Iron nail, an Aluminium wire, A small piece of wood
Articles float on water: Charcoal. Thermocol, Cork.

Metals are substances that generally exist in the solid state, exhibit high conductivity of heat and electricity, and possess Metallic lustre and hardness.

Question 32.
What are the characteristics of non-metals in comparison with metals?
Answer:
Generally, non-metals are less hard than metals

• They do not show sonority.
• They generally do not conduct electricity.
• They generally show a very low boiling point and Melting point.

Question 33.
List some non metals in your Science Diary. Classify them into solid, liquid and gas.
Answer:

Solid	Liquid	Gas
Boron	Bromine	Hydrogen
Carbon		Nitrogen
Silicon		Oxygen
Germanium		Fluorine
Phosphorous		Chlorine
Arsenic		Iodine
Sulphur		Helium
		Neon
		Argon
		Krypton
		Radon
		Xenon

Question 34.
Observe the newly formed surface of sodium when it is cut with a knife. Record your observation.
Answer:
Good metallic lustre.

Question 35.
Observe the surface after keeping it exposed to air for some time. What change do you observe?
Answer:
Metallic lustre disappears, and the surface becomes dull or tarnished.

Question 36.
Why did it lose its metallic lustre?
Answer:
It is because sodium reacts with the components of air

Question 37.
Haven’t you noticed the dull appearance of the surface of old objects made of aluminium?
Answer:
Most metals react with the atmosphere to form various compounds, and this is the reason for their dull appearance.

Question 38.
Take an aluminium wire and scrub it with sandpaper. What change do you observe?
Answer:
When you scrub an aluminium wire with sandpaper, you observe that the dull surface becomes shiny or lustrous again.
Most metals, such as copper and magnesium, react with air in a similar manner.

Question 39.
Burn a piece of magnesium in air. What is left behind?
Answer:
Magnesium reacts with oxygen in the air to form the compound magnesium oxide.
Magnesium + Oxygen → Magnesium oxide
2Mg + O₂ → 2MgO

Question 40.
a) Dissolve the magnesium oxide formed, in water taken in a beaker. What is the colour change when a red litmus paper is dipped in it?
b) What is the reason?
Answer:
a) Red litmus paper changes to blue.
b) Magnesium oxide dissolves in water to form magnesium hydroxide, which is a base.

• Most of the metals (except silver, gold and platinum) react with oxygen in air to form the corresponding oxide.
• Almost all the metal oxides show a basic nature in the presence of water.
• Some metals react with the components of air like moisture and carbon dioxide in addition to oxygen.
  Oxides of metals are generally basic in nature.

OXIDES OF NON-METALS
Carbon combines with oxygen to form carbon dioxide.
C + O₂ → CO₂

Question 41.
Do you know how soda water is prepared?
Answer:
Soda water is prepared by dissolving carbon dioxide in water at high pressure.
CO₂ + H₂O → H₂CO₃

Question 42.
Dip a blue litmus paper in soda water. Notice the change in colour.
Answer:
When a blue litmus paper is dipped in soda water, the blue litmus paper will turn red.
It is clear that soda water is acidic in nature. Carbonic acid is present in soda water.

Oxides of nonmetals are generally acidic in nature.

Question 43.
What is Metal Corrosion?
Answer:
Metals react with different components of air and form various compounds. This is known as metal corrosion.
Examples:
Rusting of iron
Copper tarnishes.
Metals lose their lustre.

Question 44.
What are the factors that influence the rusting of iron?
Answer:

• Presence of oxygen and moisture.
• Presence of impurities.
• Temperature.
• Presence of salts like common salt accelerates the rusting process of iron.

EXPERIMENT
Materials required

Clean and dry test tubes (4), cork (4), rust-free and shiny iron nails (4), anhydrous calcium chloride, table salt, ordinary water, distilled water, boiled distilled water, and oil.

Procedure
Take four test tubes. Put a rust-free and shiny iron nail in each of them. Add distilled water in the first test tube, salt solution in the second test tube and distilled water soon after boiling in the third test tube. Iron nails should be fully immersed in these three test tubes. Add oil in the third test tube in such a way that the surface of the water is completely covered by oil. Take anhydrous calcium chloride or quicklime in the fourth test tube. All the four test tubes should be closed immediately with cork after putting the materials.

Question 45.
Keep the test tubes at rest for a few days and watch the iron nails afterwards. Indicate the test tubes in which the iron nails got rusted.
Answer:
The iron nails in the first and second test tubes have rusted.
Air and moisture are present in the first test tube.
The salt solution in the second test tube influences the rusting of iron.

Question 46.
The iron nails in the third and fourth test tubes haven’t undergone any change. What is the reason?
Answer:
Since the third test tube contains distilled water soon after boiling and oil floating on the surface of water, the iron nail cannot come in contact with air. Anhydrous calcium chloride or quicklime absorbs the moisture present in the fourth test tube.

Anhydrous calcium chloride absorbs moisture from atmosphere very quickly. Silica gel and quick lime are also used for this purpose.

Question 47.
Why was boiled distilled water used in this experiment?
Answer:
To completely remove air and achieve a high temperature.

Question 48.
Do you know why iron window bars in houses close to the seashore corrode faster?
Answer:
The presence of salt in the atmospheric air causes faster rusting of iron.

Question 49.
Besides iron, which other metals are used in our daily life that undergo corrosion in the presence of atmospheric air?
Answer:

• Copper
• Aluminium
• Silver
• Zinc

Question 50.
Very reactive metals like sodium and potassium are stored in kerosene. Can you find the reason for it?
Answer:
Highly reactive metals quickly undergo chemical reactions in the presence of air and moisture. They are stored in kerosene to avoid contact with air and moisture.

Question 51.
After cutting a lemon, if the iron knife is left without wiping, it starts rusting faster. You are familiar with the acid present in lemon, aren’t you?
Answer:
Iron rusts faster in the presence of acids. Citric acid is present in lemon.

Question 52.
Why are food items with having sour taste, such as pickles and curd, are not stored in vessels made of aluminium and Iron?
Answer:
Sour substances contain acids (pickles – acetic acid, curd – lactic acid). Metal vessels react with these. Therefore, pickles and curd are not stored in metal vessels.

Question 53.
Do all metals similarly undergo corrosion?
Answer:
Metals that react with components in the atmospheric air are susceptible to corrosion. Less reactive metals, such as gold, Platinum, and Silver, do not corrode quickly.

Question 54.
What are the disadvantages of the corrosion of metals

• Causes metals to lose their shine and original appearance, becoming dull or discoloured.
• Environmental Pollution
• Results in economic loss
• Leads to structural failures (bridges, buildings), leaks, and explosions in pipelines
• Mechanical failures in vehicles and aircraft.

Question 55.
What are the methods to prevent corrosion?
Answer:

• Painting
• Greasing/Oiling
• Galvanisation
• Apply Non-Metallic coating
• Convert to alloys

Question 56.
What are alloys?
Answer:
Metals are combined-with other metals or non-metals to make alloys.
It is done to obtain materials with desirable properties and to resist corrosion.
A very small number of non-metals like carbon, phosphorous, etc. are also added to such alloys.
For e.g:-stainless steel, brass, bronze

Question 57.
What are the advantages of alloying metal?
Answer:

• Increased strength and Hardness
• Preventing corrosion
• Improve appearance
• Improved Durability

Question 58.
The presence of certain metals is essential for the normal functioning of the human body. Give examples.
Answer:
Sodium, Potassium, Calcium, Iron, Cobalt and Zinc are examples of such metals.

Question 59.
Name the metal contained in haemoglobin in the blood is?
Answer:
Iron

Question 60.
Name the most abundant metal in the human body?
Answer:
Calcium

• It gives strength to bones and teeth.
• It helps to regulate blood pressure.

As the human body cannot synthesise those metals, they should be made available through food in sufficient quantities.

Class 8 Basic Science Chapter 6 Question Answer Extended Activities

Question 1.
Alloys have a variety of uses. Duralumin, which is used to make the parts of aircrafts and Alnico, which is used to make magnets are examples. Collect information about the alloys and their uses. Present it in your class as slides or charts.
Answer:
Hints

Alloys	Components	Uses
Steel	Fe, C	Used for the manufacture of tools, Building materials, bridges, and railway tracks
Stainless Steel	Fe, Ni, Cr, C	To manufacture household appliances and surgical instruments
Brass	Cu. Zn	To make locks, handles, and musical instruments
Bronze	Cu, Sn	To make medals, statues, musical instruments, etc.
Alnico	Al, Ni, CO, Fe	To make permanent magnets
Duralumin	Al, Cu, Mg, Mn	To make aircraft parts
Magnalium	Mg, Al	To make aircraft parts
Nichrome	Ni, Cr, Fe, C	To make heating coils
Solder	Sn, Pb	To connect electric wires
Ornamental Gold	Au, Zn/Ag	To make jewellery and coins

Question 2.
Metals are present not only in the human body, but in plants as well. Collect information regarding the important metals present in plants and their functions. Prepare a science article based on this.
Answer:
Metals in the plant body

• Magnesium – The main component of chlorophyll Helps in photosynthesis
• Potassium, Calcium – Helps with growth and nutrition
• Cobalt, Iron, Manganese, Copper, Molybdenum, Nickel, Zinc – Plays an important role in growth, enzyme production, and metabolic functions

Metals and Non Metals Class 8 Notes

Class 8 Basic Science Metals and Non Metals Notes Kerala Syllabus

• Metals are substances that generally exist in the solid state. Show high conductivity of heat and electricity, metallic lustre and hardness.
• Generally, metals can be hammered and flattened into thin sheets. This characteristic property of metals is known as malleability.
• Gold is the most malleable metal.
• Metals can be drawn into thin wires. This property of metals is known as Ductility.
• Metals like gold and copper can be drawn into very fine wires. Gold and Platinum are the most ductile metals.
• The ability of a material to conduct electricity through it is known as electrical conductivity. All metals are electrical conductors.
• Silver is the best electrical conductor among the metals.
• The ability of metals to conduct heat, viz., thermal conductivity, is one of the fundamental characteristics of metals.
• Silver is the best conductor of heat among metals.
• The ability of metals to produce characteristic sound when striked with a hard material is known as sonority.
• The shiny appearance of the surface of metals is known as metallic lustre.
• Generally, metals are hard.
• Metals generally have high melting point.
• Metals generally have high boiling points.
• Metals generally have high density.
• Characteristics of Non-Metals
  • Generally, non-metals are less hard.
  • They do not show sonority.
  • They generally do not conduct heat.
• Reactions of metals with atmospheric air
  • Most of the metals (except silver, gold and platinum) react with oxygen in air to form the corresponding oxide. Almost all the metal oxides show basic nature in the presence of water. Some metals react with the components of air like moisture and carbon dioxide in addition to oxygen.
• Oxides of metals are generally basic in nature.
• Oxides of non-metals are generally acidic in nature.
• Metals react with different components of air and form various compounds. This is known as corrosion of metals.
• Metals are combined with other metals or non-metals to make alloys. It is done to obtain materials with
  desirable properties and to resist corrosion. A very small amount of non-metals like carbon, phosphorus, etc. are also added to such alloys.
• Essential metals like sodium, potassium, calcium, iron, cobalt, and zinc are crucial for normal human body functioning, with calcium being the most abundant and vital for bones, teeth, and blood pressure regulation. Since the body cannot synthesise these, they must be obtained in sufficient quantities through diet.

INTRODUCTION

It can be observed that most of the elements discovered so far are metals. The discovery and use of metals greatly accelerated the pace of human progress. Tools, machinery, construction materials, vehicles, bridges, railway tracks, ornaments, and household appliances are just a few of the numerous objects made from metals. Certain characteristics of metals make them beneficial for various uses. This unit will delve into the specific characteristics of metals that make them so versatile and invaluable, covering topics like malleability, ductility, electrical and thermal conductivity, sonority, metallic lustre, and hardness. Metals undergo corrosion due to interaction with the atmosphere. In this unit, we will understand the causes of metal corrosion and methods to prevent it, as well as the properties of non-metals.

ELECTRICAL CONDUCTIVITY
Complete the circuit as shown in the figure

A few materials are given on the table. Put them one by one in the place marked as P, Q. Repeat the experiment using more objects. Record the observation and inference.

Object	Bulb glows/does not glow	Conductor of electricity /not a conductor of electricity
A folded piece of paper	Bulb does not glow	Not a conductor of electricity
A piece of plastic scale /ruler	Bulb does not glow	Not a conductor of electricity
A piece of a razor blade	Bulb glows	Conductor of electricity
A fine iron wire	Bulb glows	Conductor of electricity
Aluminum wire	Bulb glows	Conductor of electricity
Jute	Bulb does not glow	Not a conductor of electricity
Piece of cloth	Bulb does not glow	Not a conductor of electricity
Copper wire	Bulb glows	Conductor of electricity
Rubber band	Bulb does not glow	Not a Conductor of electricity

SONORITY
The ability of metals to produce a characteristic sound when strike with a hard material is known as sonority.

METALLIC LUSTRE
The shiny appearance of the surface of metals is known as metallic lustre.
Certain metals show metallic lustre when they are cut into pieces or polished.

HARDNESS
You know that it is easy to cut sodium metal with a knife.

PROPERTIES OF METAL
• Generally, metals are hard
Metals generally exist in the solid state.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 7 Let’s Cultivate and Reap Goodness Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 7 Let’s Cultivate and Reap Goodness Question Answer Notes

Class 8 Basic Science Chapter 7 Notes Kerala Syllabus Let’s Cultivate and Reap Goodness Question Answer

Let’s Cultivate and Reap Goodness Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Arrange the information given in boxes A and B in the table suitably.

Answer:

Space constraints	Synthetic fertiliser	Organic fertiliser
Vertical farming.	Urea	Manure
Terrace farming	Ammonium phosphate	Vermicompost
Sack farming	Superphosphate	Bone meal

Question 2.
Satheesh has 15 cents of homestead land and 30 cents of paddy field. He says that paddy cultivation is not profitable. What suggestions do you have to make farming profitable by making use of the homestead land and the paddy field?
Answer:
Integrated farming methods can be adopted. There is potential for vegetable cultivation, papaya cultivation, poultry farming, and cattle farming on the land. There is potential for duck farming and rearing of fishes along with paddy cultivation in the field.

Question 3.
Which is the odd one? What are the common features of the others?
a) Wick irrigation, Vertical farming, Drip irrigation, Mulching
b) Hydroponics, aquaponics, aeroponics, geographical indication
Answer:
a) Vertical farming, others are various irrigation methods.
b) Geographical indication, others are parts of smart farming.

Question 4.
‘Farming will be profitable only if all the pests are killed!’ What is your response to this comment from a farmer? How can effective pest control be implemented?
Answer:
I do not agree with this opinion of the farmer. Pest control methods should be selected taking into account the density and nature of the crops. The farmers’ need is not to kill the entire pests, but to control their growth in a way that does not damage the crops. Integrated pest control is a method that minimises the use of pesticides through automated pest control methods using various types of /lets and traps, friendly insects, and the cultivation of seeds that are resistant to pests.

Question 5.
Observe the illustration.

a) What are the benefits to farmers by producing such products?
b) Prepare a similar illustration of any other crop.
Answer:
a) The farmer’s income increases through the marketing of value-added products. New employment opportunities arise.

b) Pineapple jam, pineapple juice, pineapple squash, pineapple leaf fiber, pineapple wine, pineapple candy, dried pineapple pieces, pineapple vinegar, pineapple pickle.

Basic Science Class 8 Chapter 7 Question Answer Kerala Syllabus

Answers to the indicators on page no. 104
Question 1.
What are the ideas you have learned from the news reports?
Answer:

• A school student has caught the media’s attention by developing a simple machine for harvesting cassava.
• The little scientist has applied for a patent for his invention.
• A young farmer with a higher degree sells banana leaves when the price of banana leaves is low.
• He earns a good income by exploiting the market potential of nutritious leafy vegetables.
• He earns income by making several value-added products from turmeric
• He uniquely cultivates the rare Gandhakashala rice and markets it under a special brand, earning good sales.

Question 2.
What are the circumstances that have prompted farmers to choose new ways?
Answer:

• The use of light machinery for harvesting cassava has made harvesting easier.
• A unique idea that banana leaves can be sold when they are cheap.
• Utilising the market potential of nutritious leafy vegetables.
• Due to the fall in price of turmeric during the harvest, several value-added products have been created from turmeric and brought to the market.
• Gandhakshala rice, which is being grown elsewhere, is being cultivated in a unique way and brought to the market under a special brand.

Question 3.
What are the other possibilities to make farming profitable?
Answer:

• Construction of simple machines to save time and effort in farming.
• The sale potential of not only fruits but also other parts of plants, such as leaves.
• Value-added products from agricultural products.
• Agricultural products are branded and marketed in a special way.
• Growing crops that have high demand in the market.

Question 4.
Completed illustration 7.1

Answer:

Observe figure 7.3 (pg. no. 107) and prepare a note based on the indicators through discussion.

Question 5.
How does it help to overcome space constraints?
Answer:
Vertical farming uses shelves or stacked layers to grow plants upwards, allowing more crops to be grown in a smaller space.

Question 6.
How does it ensure availability of light?
Answer:
The plants are arranged in such a way that all layers receive sufficient sunlight.

Question 7.
How does it help to reduce the use of water?
Answer:
Since water drips from the top layer to the bottom, many plants reuse the same water, thereby conserving it.

Question 8.
How to Control Construction Costs?
Answer:
If you use waste materials like plastic bottles, old wood, and containers, the cost is lower. Otherwise, the cost will increase.

Answers of Indicators, Page No. 108 from the Textbook
Question 9.
Macronutrients and Micronutrients:
Answer:
Plants obtain the elements they need from the soil. Of these, nitrogen, potassium, phosphorus, calcium, magnesium, and sulfur are the elements that are required in large quantities. These are called macronutrients. However, elements like barium, boron, zinc, copper, manganese, iron, molybdenum, chlorine, and nickel are required in very small quantities and are known as micronutrients.

Question 10.
Need for the application of fertilisers:
Answer:
Fertiliser is applied to ensure the availability of all the elements necessary for crops to grow.

Analysis of Table 7.1, Pg.no. 110

Question 11.
Why is it necessary to include local vegetables in the diet?
Answer:
We can also get all the elements that plants get in various forms by consuming them. Native vegetables like Colocasia leaf, curry leaves, Drumstick leaves, and Sweet amaranth contain more protein, fiber, starch, calcium, iron, carotene, and vitamin C than other vegetables.

Question 12.
Observe the illustration 7.3 showing the methods of production of high-yield planting materials. Prepare notes on it.

(a) Grafting

• The process of joining the stem of one plant with the stem, including the roots, of another plant to form a single plant.
• Used in plants such as Mango tree and roses.
• Property: Combines the properties of both plants.

(b) Budding

• A method of attaching a bud from one plant to the stem of another plant.
• Used in roses, lemons, etc.
• Advantage: Faster production

(c) Layering

• A branch of a plant is bent to the ground and covered with soil to grow roots. Later, it is cut and planted.
• Used in jasmine, peach, strawberry, etc.
• Advantage: New plants are similar to the mother plant.

(d) Tissue culture

• Seedlings are produced by isolating tissues from suitable parts of the plant and growing them in a special nutrient medium.
• Used in bananas and orchids.
• Benefits: Rapid production of large numbers of healthy, disease-free plants.

(e) GM crops (Genetically Modified Crops)

• These are crops that have had their genes altered in a lab to improve their characteristics. Their production requires strict safety testing.
• Examples: Bt cotton, golden rice.
• Properties: Pest resistance, superior qualities, high yield.

(f) Hybridisation

• The process of crossing two plants with different traits to produce a new plant with superior traits.
• Used in wheat, rice, and tomatoes.
• Advantages: High yield, disease resistance.

Figure 7.10 Cartoon Analysis on page 113

Question 13.
What are the problems farmers face regarding water use?
Answer:
Heavy rain, floods, droughts, and water scarcity

Question 14.
What are the suggestions to solve the problems faced by farmers regarding water use?
Answer:
Water from heavy rainfall is stored in dams and reservoirs. The stored water is then transported to farmlands through systems such as canals during times of water scarcity.

Answers to the indicators on page 114
Question 15.
What are the main pests affecting crops in our region?
Answer:
Pod borer (Legume), Leaf-rolling Caterpillar (Okra), Stem Borer (Brinjal)

Question 16.
What are the various methods adopted by farmers in your area to control pests?
Answer:

• Use of chemical pesticides
• Use of natural enemies of pests (biological control)
• Use of biological pesticides.
• Farmers change the type of crop grown in a field each season. This prevents pests from multiplying because they do not get the same crop to attack each time.
• Use of pest-resistant varieties.
• Keeping the fields clean.
• Weeds and debris are removed from the fields regularly. This prevents pests from hiding in the fields and breeding.

Answers to the indicators on page no. 116, by analysing illustration 7.4

Question 17.
Integrated farming- advantages and possibilities:
Answer:
(a) Benefits of integrated farming:

• Better use of resources.
• No resources are wasted. Animal waste is used as fertiliser for plants. Water is reused.
• More income for farmers
• Farmers get income not only from crops, but also from selling milk, eggs, fish, and vegetables.
• Even if one crop (like a bad crop) fails, other crops (like fish or eggs) provide income.

(b) The possibilities of integrated farming:

• It can be used in villages, small farms, and even in urban areas where there is space.
• Helps in self-employment and sustainable agriculture.
• Promotes organic farming and protects the environment.

(c) Food security

• Integrated farming produces non-toxic food.
• There is less need for pesticides or artificial feed.
• It improves nutrition for families and consumers.

(d) Reducing production costs

• Money is saved on fertilisers and feed. Because the residue of one is used as fertiliser for the other.
• Waste is recycled efficiently.
• The need to buy products from outside will be reduced.

Answers to the indicators on page no. 119, based on illustration 7.6

Question 18.
What are the benefits of diversifying agriculture?
Answer:
Agriculture is not just about producing food. Farming for Banana leaves, horticulture, Poultry farming, medicinal plant cultivation, Betel cultivation, floriculture, ornamental fish farming, and raising pets are all ways of diversifying agriculture.

Benefits:

• More sources of income – Farmers can earn money from many activities, not just from one crop.
• Even if one crop fails, income can be generated from other crops.
• Efficient use of land and resources – Different activities can be done in the same area by using waste from one activity for another.
• Employment for more people
• Helps small families and women to get work done from home.
• Supports local markets and economies

Question 19.
Which of these can be done even by those with limited space?
Answer:

• Medicinal plant cultivation – on terraces, balconies or small gardens
• Rearing of chickens – in backyards or coops
• Ornamental fish rearing – in small tanks or containers
• Floriculture – in pots or small plots
• Raising of pets – at home
• Betel cultivation – in shaded areas or along fences

Class 8 Basic Science Chapter 7 Question Answer Extended Activities

Question 1.
Find out the common plant diseases in your area. Prepare a pictorial chart listing their pathogens, mode of transmission, symptoms and remedies and display it on the bulletin board.
Answer:

Diseases	Causative organism (Pathogen)	Symptoms	Mode of transmission	Remedial measures
Blight disease in Rice	Bacteria	The tips of the leaves turn yellow, and the leaves become dry.	Through infected seeds, rain, and wind	Avoid diseased seeds.
Wilt disease in Banana	Fungus	The leaves turn yellow and wilt.	Through soil, and through water	Destroy infected plants.
Mosaic disease in Tapioca	Virus	Mosaic pattern on leaves	Through insects	Use healthy seedlings and control pests

Question 2.
Collect information about the major agricultural research institutes in Kerala and their contributions to the agricultural sector, and prepare a list of them.
Answer:

• Kerala Agricultural University, Thrissur – Research on crops. Training for farmers
• Indian Institute of Spices Research, Kozhikode – Research on spices like ginger, pepper and turmeric
• Central Tuber Crops Research Institute, Thiruvananthapuram – Research on tuber crops
• Rubber Research Institute of India, Kottayam – Production of good varieties of rubber

Question 3.
You know that many machines are used in the agricultural sector to reduce human effort. The results of thinking about how to alleviate the difficulties of farmers led to the discovery of most of the machinery seen today. Design a model of an innovative device that will be useful to the farmers in your area.
Answer:
Hint: Think about common issues experienced by small-scale farmers in a tropical, monsoon-affected area, particularly related to labor and resource management.
(An example is given below for you…)
Farmers in Kerala, particularly those cultivating crops like coconuts, spices, and various vegetables, often face challenges such as:

• Labor Shortage & Cost
• Nutrient Management
• Post-Harvest Damage
• Accessibility
• Environmental Concerns

Device Name: Coco-Smart Harvester & Nutrient Analyzer.
The Coco-Smart Harvester & Nutrient Analyzer is a semi-autonomous, drone-based system designed to efficiently harvest tree-borne products (initially focusing on coconuts and later adaptable for other tall tree crops) while simultaneously assessing the nutrient needs of the tree/soil and delivering targeted solutions.

Operational Workflow:

1. Pre-Flight Planning: Farmer maps out the area using a user-friendly tablet app, identifying trees for harvesting or analysis.
2. Automated Scan & Analysis: The drone flies autonomously over the designated trees, conducting a hyperspectral scan and, if needed, deploying the soil sensor.
3. Harvesting (if applicable): Based on visual recognition (AI-powered to identify ripe products) and farmer input, the drone’s robotic arm engages the harvesting mechanism, gently collecting the product.
4. Nutrient Recommendation: The AI analyses the data and provides precise nutrient recommendations to the farmer’s app, indicating which trees need what specific nutrients and in what quantities.
5. Targeted Application: The drone can then be programmed to autonomously apply the recommended nutrients via its micro-dosing sprayer or granular dispenser.
6. Data Logging: All data (harvest quantity, nutrient status, application history) is logged for future analysis and improved farm management.

The Coco-Smart Harvester & Nutrient Analyzer aims to be a game-changer for farmers in Kerala, addressing critical challenges with a blend of robotics, AI, and precision agriculture.

Let’s Cultivate and Reap Goodness Class 8 Notes

Class 8 Basic Science Let’s Cultivate and Reap Goodness Notes Kerala Syllabus

• Innovative agricultural initiatives can strengthen rural economies, enhance food security, and inspire future generations to engage in farming.
• Various farming methods to make use of most of the space include sack farming, aquaponics, pet bottle farming, vertical farming, pot cultivation, and terrace farming.
• Elements that plants need in large quantities are called macronutrients and elements that plants need in small quantities are called micronutrients.
• Fertilisers are used to ensure the availability of all the elements that plants need to grow.
• Different types of fertilisers used in agriculture – organic fertilisers, artificial fertilisers, nano fertilisers, and biofertilisers.
• Grafting, budding, layering, and tissue culture are methods used to produce seedlings that have the same characteristics as the parent plant.
• GM crops are crops that can incorporate new characteristics into crops by changing the genetic structure through genetic engineering.
• Tissue culture is a technology that helps produce large numbers of plants that have the same characteristics as the parent plant.
• The greenhouse is made of sheets like plastic, nylon, and polyethene. It also helps in reducing the incidence of pests and diseases as it is covered on all sides.
• Drip irrigation is an irrigation method that uses pipes and valves to drop water into the root zone.
• Wick irrigation is a method of delivering water directly from a water source to the root zone of plants with the help of a cotton wick.
• Mulching is a traditional method of covering the soil in agricultural fields with leaves and straw to reduce water loss due to evaporation.
• Integrated pest control is a method that minimises the use of pesticides through automated pest control methods using various types of nets and traps, friendly insects, and the cultivation of seeds that are resistant to pests.
• Integrated farming is the management of diverse organisms together.
• Smart farming is the effective use of modern technologies in agriculture, such as hydroponics, aeroponics, etc.
• Depending on the characteristics of the land where the products are grown, there will be differences in the taste, colour, smell and nutritional value of the products. On the basis of this, agricultural products produced in some areas are given Geographical Indication (GI) status.
• There are apps that provide weather warnings, pest and disease warnings, expert advice on agriculture, market price levels and information about benefits for farmers.

INTRODUCTION

In a world that often feels overwhelmed by challenges and negativity, the concept of “cultivating and reaping goodness” offers a powerful and hopeful perspective. This idea isn’t just a feel-good platitude; it’s a profound call to action, urging us to intentionally nurture positive qualities, actions, and intentions within ourselves and our communities. Just as a farmer carefully tends to their crops, preparing the soil, planting seeds, and providing consistent care, we too can consciously foster an environment where goodness can flourish. This process involves recognising that every small act of kindness, every moment of empathy, and every effort to uplift others contributes to a larger harvest of positive outcomes. When we actively cultivate goodness, we not only transform our own lives but also create a ripple effect, inspiring and empowering those around us to do the same. Ultimately, this journey is about understanding that the positive impact we wish to see in the world begins with the seeds we choose to plant today. In this chapter, we will deal with various agricultural initiatives, careful utilisation of land, application of fertilisers, use of high-quality planting material for getting better yield, water utilisation and pest control measures and integrated farming in detail.

AGRICULTURAL INITIATIVES

• The ‘Karshaka Pratibha’ Puraskar is an award given by the state government to the best student farmer.
• Innovative agricultural initiatives can strengthen rural economies, enhance food security, and inspire future generations to engage in farming.

MAXIMISING LAND UTILISATION

• Various farming methods to make use of most of the space include sack fanning, aquaponics, pet bottle farming, vertical farming, pot cultivation, and terrace farming.
• Vertical farming is an innovative way to overcome space constraints.

APPLICATION OF FERTILISERS

• Elements that plants need in large quantities are called macronutrients.
• Elements that plants need in small quantities are called micronutrients.
• Fertilisers are used to ensure the availability of all the elements that plants need to grow.
• Different types of fertilisers used in agriculture – organic fertilisers, artificial fertilisers, nano fertilisers, and biofertilisers.

• All the elements that plants get are also available to us as food in various forms.
• Native varieties will grow in harmony with the local environment.

FOR BETTER YIELD, HIGH QUALITY PLANTING MATERIALS

• Grafting, budding, layering, and tissue culture are methods used to produce seedlings that have the same characteristics as the parent plant.
• GM crops are crops that can incorporate new characteristics into crops by changing the genetic structure through genetic engineering.
• Tissue culture is a technology that helps produce large numbers of plants that have the same characteristics as the parent plant.

UTILISATION OF WATER AND PEST CONTROL
UTILISATION OF WATER

• A greenhouse is a system that helps in cultivating crops both in the rainy season and in the summer.
• Drip irrigation is an irrigation method that uses pipes and valves to drop water into the root zone.
• Wick irrigation is a method of delivering water directly from a water source to the root zone of plants with the help of a cotton wick.
• Mulching is a traditional method of covering the soil in agricultural fields with leaves and straw to reduce water loss due to evaporation.

PEST CONTROL

• Although there are different methods for pest control, the population density of pests and the nature off the crops should be taken into account when choosing the pest control methods.
• Farmers do not want to kill all the pests, but rather control their growth in a way that does not damage the crops.
• Integrated pest control is a method that minimises the use of pesticides through automated pest control methods using various types of nets and traps, friendly insects, and the cultivation of seeds that are resistant to pests.

INTEGRATED FARMING

• Integrated farming is the management of diverse organisms together.
• Smart farming is the effective use of modern technologies in agriculture.
• Hydroponics – Plants are grown in nutrient solutions, and the amount of nutrients is detected with the help of sensors and provided as needed.
• Aeroponics – Water and nutrients are provided to the roots growing in the air in a timely manner with the help of sensors.
• If a system is set up for consumers to see the process from sowing to harvesting, the reliability and market value of the products can be increased.
• Depending on the characteristics of the land where the products are grown, there will be differences in the taste, colour, smell and nutritional value of the products. On the basis of this, agricultural products produced in some areas are given Geographical Indication (GI) status.
• Agriculture is not only about producing food.
• There are apps that provide weather warnings, pest and disease warnings, expert advice on agriculture, market price levels and information about benefits for farmers.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 8 Origin of Life, Origin of Living Things Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 8 Origin of Life, Origin of Living Things Question Answer Notes

Class 8 Basic Science Chapter 8 Notes Kerala Syllabus Origin of Life, Origin of Living Things Question Answer

Origin of Life, Origin of Living Things Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Write which of the given statements are not related to eukaryotes.
a) A clear nuclear membrane is seen.
b) Cell organelles have no membranous covering.
c) Genetic material is found inside the nuclear membrane.
d) Organelles that perform various functions are seen.
Answer:
b) Cell organelles have no membranous covering.

Question 2.
Arrange the timeline properly.

Answer:

Question 3.
Match the following.

Answer:
a) Urey- Miller – Amino acids
b) Joan Oro – Nitrogenous bases
c) Sidney Fox – Proteinoid
d) Oparin-Haldane – Theory of Chemical evolution

Basic Science Class 8 Chapter 8 Question Answer Kerala Syllabus

Answers to the indicators on page no. 125
Question 1.
Characteristics of the primitive Earth’s atmosphere
Answer:

• High temperature.
• Hydrogen, methane, carbon dioxide, hydrogen sulfide, ammonia, water vapour.
• No free oxygen.

Question 2.
Formation of Ocean
Answer:
The condensation of steam, prolonged rainfall and the formation of oceans. The ocean is formed by dissolving varidus substances.

Question 3.
Energy sources that assist the formation of biomolecules.
Answer:
Sunlight, Lightning, Ultraviolet Rays, Volcanic Eruptions.

Question 4.
Formation of primitive cell
Answer:
The condensation of steam, prolonged rainfall and the formation of o’ceans. The ocean is formed by dissolving various substances. Simple organic particles were formed in the seawater. Then, complex organic particles were formed from simple organic particles. A complex molecule called nucleic acid and a fat layer were formed. Then, a primitive cell capable of self-replication was formed.

Question 5.
Completed table 8.1

Answer:

Indicators	Conditions in the primitive Earth	Experimental set-up
Gases	Hydrogen, Methane, Carbon dioxide, Hydrogen sulphide, Ammonia, Water vapour.	Methane, ammonia, hydrogen, Water vapour.
Energy source for chemical synthesis	Sunlight, Lightning, Ultraviolet Rays, and Volcanic Eruptions.	Energy from an electric spark through electrodes

Question 6.
Analyse illustration 8.5 based on the indicators and record your inferences in the Science Diary

Answer:
Prokaryotic cell: A few cell organelles, Cell organelles have no membranous covering, Membrane-bound nucleus absent.
Eukaryotic cell: Many cell organelles, Organelles with a membranous covering, Membrane-bound nucleus present.

Question 7.
Analyse illustration 8.6 from the textbook page number 128 and prepare a note on it.

Answer:
The eukaryotic cell engulfs the small aerobic bacteria. Instead of digesting the small cell, it protects it. These eventually become mitochondria. The eukaryotic cell engulfs the tiny photosynthetic bacteria. Instead of digesting the photosynthetic bacteria, it protects them and gradually transforms them into chloroplasts.

Question 8.
Completed Table 8.2, Pg.no. 129

Answer:

Indicators	Prokaryotic cell	Eukaryotic cell
Structure	Simple	Complex
Nucleus	Membrane-bound nucleus absent	Well-defined nucleus with a membrane covering
Cell organelles such as mitochondria and chloroplasts	Absent	Present

Question 9.
Analyse the timeline (Table 8.3) from Textbook Pg.no. 130, and prepare’ a note based on it.

Answer:
4 – 4.6 billion years ago: Origin of the Earth
3.5 – 2.5 billion years ago: Formation of the first life. Single-celled prokaryotes with simple structures
2.5 – 541 million years ago: Multicellular organisms called eukaryotes
541 – 252 million years ago: Plants and animals on land
252 – 66 million years ago: Dinosaurs
66 million years ago to the present: Emergence of mammals, evolution of humans

Question 10.
Conclusions drawn from the analysis of Illustration 8.7 on page 131 of the textbook

Answer:
Suppose we are preparing a calendar assuming the age of the universe to be just one year. One second in the said calendar is equivalent to approximately 438 years. Conclusions drawn from analyzing a model of the cosmic calendar:
The universe is born at exactly 00.00 on January 1st
August 1st Solar System, Earth
September 22nd Emergence of life
October 12th Prokaryotes
November 9th Eukaryotes
December 18th Vertebrate
December 20th Land Plants
December 26th Dinosaurs
December 27th Mammals
December 31st, 11.52 PM – Human
According to the cosmic calendar, man was born in the last moments of the last day of the year. This shows how recent the emergence of man is in the chronology of the universe.

Class 8 Basic Science Chapter 8 Question Answer Extended Activities

Question 1.
Make a model of the Urey-Miller experimental setup using the materials available from the surroundings and display it at the science corner.

Question 2.
Prepare a digital model/chart of the Cosmic calendar including more information and exhibit in the classroom.

Origin of Life, Origin of Living Things Class 8 Notes

Class 8 Basic Science Origin of Life, Origin of Living Things Notes Kerala Syllabus

• Scientists believe that life originated on Earth about 3.5 billion years ago.
• Theories related to the origin of life – Panspermia theory, Chemical evolution theory
• Harold Urey, Stanley Miller, Sydney Fox, and Joan Oro are some of the scientists who contributed to the field of the origin of Life.
• The simple structured cells, which were formed in the beginning, are called prokaryotes, and Eukaryotic cells with more complex structures are evolved from prokaryotic cells.
• As part of the evolutionary process, the formation of a nuclear membrane was the key feature of eukaryotic cells. Additionally, membrane-bound organelles were evolved, enabling them to perform specialised functions.
• Around 3.8 billion years ago, primitive living cells were formed from the molecules present in Earth’s oceans. By 3.5 billion years ago, prokaryotic cells had evolved.
• Approximately 2.5 billion years ago, the occurrence of photosynthesis led to the release of oxygen into the atmosphere. Later, eukaryotic, cells with organelles such as mitochondria and chloroplasts were evolved. Over time, simple multicellular organisms appeared around 800 million years ago, followed by more complex life forms.
• The Cosmic Calendar is a depiction that helps to easily understand the chronology from the creation of the universe to the origin of human beings.

INTRODUCTION

The quest to understand the origins of life is one of the most profound and challenging scientific endeavours. It delves into the fundamental question of how inanimate matter transitioned into the complex, self-replicating systems we recognise as living organisms. This field encompasses two closely related yet distinct concepts: the origin of life and the origin of living organisms.

The origin of life, often referred to as abiogenesis, explores the initial emergence of life from non-living chemical compounds. This involves understanding the conditions on early Earth—its atmosphere, oceans, and energy sources – that could have facilitated the formation of fundamental organic molecules like amino acids, nucleotides, and fatty acids. It further investigates how these simple building blocks could have self-assembled into more complex polymers (proteins, nucleic acids) and eventually organised into self-replicating systems enclosed by primitive membranes, forming the very first “protocells or primitive cells.”

The origin of living things, on the other hand, broadly refers to the subsequent evolution and diversification of these initial life forms into the vast array of organisms we see today, from the simplest bacteria to complex multicellular plants and animals. While the origin of life focuses on the first step, the origin of living things traces the evolutionary journey, driven by natural selection, adaptation, and genetic changes, that led to the incredible biodiversity on Earth. This includes the development of complex cellular structures (eukaryotes), the emergence of multicellularity, and the evolution of different modes of nutrition and reproduction.

Together, these two areas of inquiry seek to unravel the complete narrative of life’s emergence and evolution on our planet, providing insights into our own existence and the potential for life elsewhere in the universe. In this chapter, we will learn about these concepts.

ORIGIN OF LIFE

• Millions of years ago, life on Earth was very different from what we see today.
• Living things evolved in many ways, depending on changes in external factors such as habitat, climate, and food availability, as well as changes in the internal components of living cells, and the living things we see today were formed.
• Scientists believe that life originated on Earth about 3.5 billion years ago.
• Some of the simpler organisms released oxygen through photosynthesis, which led to the formation of more complex organisms.
• Complex plants and animals evolved. Over time, organisms evolved into the modern-day
• Theories related to the origin of life – Panspermia theory, Chemical evolution theory

Panspermia Theory Life originated elsewhere in the universe and was accidentally transported to Earth in the form of microorganisms or spores. These microscopic particles are referred to as Panspermia.

Chemical Evolution Theory The Chemical Evolution Theory explains that life originated as a result of changes in the combination of chemical substances in the ocean under the unique conditions of the primitive Earth.

• Although many theories explaining the origin of life have emerged over time,-the theory of chemical evolution is the one that is most supported by evidence and has received the most acceptance in the scientific world.
• Some of the scientists who contributed to this field:
  

  Harold Urey, Stanley Miller: They together proved that the fundamental units responsible for the origin of life can form from simple gases. Sydney Fox: Proved that molecules similar to proteins can be synthesised artificially. Joan Pro: Adenine, one of the key building blocks of nucleic acids, was artificially synthesised.

• Among the many experimental evidence supporting the theory of chemical evolution, the most notable is the Urey-MiUer experiment.
• The Urey-Miller experiment was conducted by artificially recreating the conditions of the primitive Earth in a laboratory.
• The Urey-Miller experiment demonstrated that organic molecules can form from inorganic components under suitable conditions.

FROM PRIMITIVE CELLS TO COMPLEX ORGANISMS

• The primitive cell is composed of nucleic acids capable of self-replication and a lipid layer covering it.
• Primitive forms like bacteria evolved from this primitive cell.
• These simple structured cells, which were formed in the beginning, tire called prokaryotes.
• Eukaryotic cells with more complex structures evolved from prokaryotic cells.

Prokaryotic cell • A few cell organelles. • Cell organelles have no membranous covering. • Membrane-bound nucleus absent.

Eukaryotic cell • Many cell organelles. • Organelles with membranous covering • Membrane-bound nucleus present.

• The eukaryotic cell engulfs the small aerobic bacteria. Instead of digesting the small cell, it protects it. These eventually become mitochondria.
• The eukaryotic cell engulfs the tiny photosynthetic bacteria. Instead, of digesting the photosynthetic bacteria, it protects them and gradually transforms them into chioroplasts.
• In prokaryotes, genetic material is scattered within the cytoplasm.
• As part of the evolutionary process, the formation of a nuclear membrane was the key feature of
  eukaryotic cells. Additionally, membrane-bound organelles were evolved, enabling them to perform
  specialised functions.
• Around 3.8 billion years ago, primitive living cells were formed from the molecules present in Earth’s oceans. By 3.5 billion years ago, prokaryotic cells had evolved.
• Approximately 2.5 billion years ago, the occurrence of photosynthesis led to the release of oxygen into the atmosphere. Later, eukaryotic cells with organelles such as mitochondria and chloroplasts were evolved. Over time, simple multicellular organisms appeared around 800 million years ago, followed by more complex life forms.

Cosmic calendar

• The Cosmic Calendar is a depiction that helps to easily understand the chronology from the creation of the universe to the origin of human beings.
• Suppose we were creating a calendar assuming the age of the universe to be just one year. One second in that calendar would be equivalent to approximately 438 years.
• According to the cosmic calendar, man was born in the final moments of the last day of the year.

The process of evolution is the cause of present biodiversity. It is difficult to predict the direction of evolution as it is an accidental phenomenon.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 4 Chemistry of Changes Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 4 Chemistry of Changes Question Answer Notes

Class 8 Basic Science Chapter 4 Notes Kerala Syllabus Chemistry of Changes Question Answer

Chemistry of Changes Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
What are the changes in the particle arrangement of substances in the activities given below?
a) Solid becomes liquid.
b) Liquid becomes gas.
c) Gas becomes liquid.
Answer:
a) Solid becomes liquid.

• Distance between the particles increases
• Attraction between the particles decreases
• Speed of movement of the particles increases
• Energy of the particle increases

b) Liquid becomes gas.

• Distance between the particles increases
• Attraction between the particles decreases
• Speed of movement of the particles increases
• Energy of the particle increases

c) Gas becomes liquid

• Distance between the particles decreases
• Attraction between the particles increases
• Speed of movement of the particles decreases
• Energy of the particle decreases

Question 2.
In the given chemical reactions, what is the main form of energy released/absorbed? Write what type of chemical reaction they are.
a) Ammonium chloride and Barium hydroxide react.
b) Copper plating on an iron bangle.
c) Glowing of firefly.
d) Decomposition of Potassium permanganate
e) Lighting an LED using lemons
Answer:

Given chemical reactions	Main form of energy released/absorbed	Type of chemical reaction
a) Ammonium chloride and Barium hydroxide reacts.	Heat energy is absorbed.	Thermochemical reaction
b) Copper plating on an iron bangle.	Electrical energy is absorbed.	Electrochemical reaction
c) Glowing of firefly	Light energy is released.	Photochemical reaction
d) Decomposition of Potassium permanganate	Heat is absorbed	Thermochemical reaction
e) Lighting an LED using lemon	Electrical energy is released.	Electrochemical reaction

Question 3.
Heat some crystals of potassium permanganate in a dry test tube. Bring a burning incense stick near the mouth of the test tube.
a) What do you observe?
b) Which is the gaseous product formed?
c) Which type of reaction is this?
Answer:
a) The incense stick flares up and burns.
b) Oxygen
c) Thermochemical reaction

Question 4.
A white cloth dipped in silver nitrate darkens when it is kept in sunlight.
a) Which form of energy is responsible for this chemical change?
b) What is the general name for this type of reaction?
Answer:
a) Light energy
b) Photochemical reactions

Question 5.
Sodium metal reacts with water to give substances.
a) Which are the reactants in this reaction?
b) Which products are formed?
Answer:
a) Sodium, Water
b) Sodium hydroxide, Hydrogen

Basic Science Class 8 Chapter 4 Question Answer Kerala Syllabus

GENERAL PROPERTIES OF MATTER

Question 1.
What do you see in the picture?
Answer:

• A candle burning
• Food is cooked
• A person sculpting or working with stone/metal
• A firecracker cone exploding
• The bunch of bananas is ripening

Substances undergo different types of changes here.

Question 2.
The stone is shaped into a sculpture, and the banana gets ripened. Are these changes of the same kind?
Answer:
No. The stone is shaped into a sculpture, is man-made, and the banana gets ripened is natural.
These changes may lead to the production of new substances.

All substances in the universe are made of matter.

GENERAL CHARACTERISTICS OF MATTER

• Has Mass
• Occupies Space (Has Volume)
• Made of Particles
• Particles have Space Between Them
• Particles Attract Each Other

EXPERIMENT:
Dip a stone hung on a thread into a beaker with a marked water level.

Question 3.
What happens to the water level?
Answer:
Water level increases

Question 4.
Why does the water level rise?
Answer:
Because the stone needs space to occupy. So, the stone displaces the water. The water level rises more.

Question 5.
What difference do you observe if a bigger stone is used?
Answer:
The water level rises more.

One of the properties of matter is that it occupies space. The space occupied by matter is its volume.

Question 6.
Weigh both the stones using a balance. What difference do you observe?
Answer:
Both stones have different masses
Matter has mass. This is another property of matter.

Mass of a substance is the measure of the quantity of matter contained in it.

Question 7.
Is air a form of matter?
Answer:
Yes, air is a form of matter.

Question 8.
Does air need space to occupy?
Answer:
Yes, air needs space to occupy.

EXPERIMENT:
Fix a towel inside a glass and immerse it upside down into the water taken in a beaker, as shown in the figure.

Question 9.
Does the towel get wet?
Answer:
The towel doesn’t get wet.

Question 10.
Why doesn’t water enter the glass?
Answer:
Because there is air inside the glass.

Question 11.
What happens to the water level in the beaker?
Answer:
The water level rises.

Question 12.
What does the difference in water level indicate?
Answer:
The volume of air

Question 13.
How can we find out whether air has mass?
Answer:
Find the mass of an uninflated football using a digital balance. After filling it with air, find the mass of the football again. You can see that the mass of the air-filled football is greater. The difference between the masses is the mass of air inside the football.
Now it is clear that the air. has mass.

Anything that occupies space and has mass is called matter.

Question 14.
What are the main states of matter?
Answer:
Matter primarily exists in three fundamental states: solid, liquid, and gas.

Question 15.
Complete the given table with respect to the three states of matter. Put the (✓) mark appropriately.

Answer:

Property	Solid	Liquid	Gas
Has definite mass	✓	✓	✓
Has definite volume	✓	✓	✗
Has a definite shape	✓	✗	✗

Question 16.
Heat some wax in a steel vessel. What happens?
Answer:
The wax melts and becomes liquid.

Question 17.
What happens when the liquid wax is cooled?
Answer:
It solidifies and becomes solid again.

Question 18.
But if a piece of paper is burnt to ash, can it be changed to paper again?
Answer:
No

Question 19.
Do all the changes occur at the same speed?
Answer:
No

Question 20.
Write more examples for slow and fast changes.

Answer:

Slow changes	Fast changes
Ice melts	Petrol bums
Milk turns into curd.	Hydrogen bums
Water turns into steam.	Acid dissolves in water.
The colour of metals fades.	Firecracker explodes
Rusting of iron	Alcohol mixes/dissolves in water.
Germination of the pea seed	Lighting a gas stove, Bursting of crackers

Question 21.
What is the difference between the burning of a piece of paper and the melting of wax?
Answer:
Burning paper is a chemical change, and the melting of wax is a physical change.

Question 22.
Classify the following changes into physical and chemical changes.
i) Curdling of milk
ii) Melting wax
iii) Burning a candle
iv) Formation of ice
v) Melting of ice
vi) Dissolution of salt in water
vii) Rusting of iron
viii) Burning of firewood
Answer:

Physical Change	Chemical Change
ii, iv, v, vi	i, iii, vii, viii

Question 23.
You have learnt about the arrangement of particles in different states of matter, i.e., solid, liquid and gas in the lower classes. Can you write about the distance and force of attraction between the particles, speed of movement and the energy of the particles in each state in the following table?

Answer:

	Solid	Liquid	Gas
Distance between the particles	very less	more than solid	very high
Attraction between the particles	very high	less than solid	very less
Speed of movement of the particles	very less	more than solid	very high
Energy of the particles	very less	higher than solid	very high

Question 24.
What happens to the distance between particles and the energy of particles when solids are heated?
Answer:
Distance between the particles: Increases
Energy of the particles: Increases

When a solid is heated, the distance between its particles and their energy increases and gradually it attains the particle arrangement of a liquid. When liquids are heated gradually, they become gases.

Question 25.
What happens when a gas is cooled?
Answer:
The distance between particles and the energy of particles decreases. Gradually, gas becomes liquid. If we further cool a liquid, it becomes solid.

SUBLIMATION
Solid substances like Camphor and Naphthalene, when heated, directly change to gases. This is known as Sublimation.

Question 26.
How does the water kept in a freezer change to ice? Discuss.
Answer:
At the low temperature inside the refrigerator, the speed of movement and energy of the molecules decrease, bringing them closer together. In this process, heat is released, and water turns into ice.
The change of substance from one physical state into another is known as a change of state.

Question 27.
Is a change of state a physical change or a chemical change?
Answer:
Change of state is a physical change

Question 28.
Which form of energy is absorbed or liberated during the change of state?
Answer:
Heat energy

Question 29.
What happens to the energy of particles when heat is absorbed or liberated?
Answer:
When heat is absorbed during a change of state, the energy of the particles increases.
When heat is liberated (released) during a change of state, the energy of the particles decreases.

Question 30.
Is the colour of potassium permanganate the same before and after the reaction?
Answer:
No

Question 31.
Take water in two beakers and add two or three crystals of fresh potassium permanganate into one of them. Add two or three crystals of the product obtained in the second beaker. Record the difference.

a. What is the change in colour you have observed?
Answer:
The pure permanganate solution is pink in colour. The solution of the substance after the reaction is green. This is due to a chemical change resulting in the formation of a new substance.

b. Is this a chemical change or a physical change?
Answer:
Chemical Change

The substances that take part in a chemical reaction are known as reactants, and the substances formed are known as products.

Question 32.
Find more examples of endothermic and exothermic reactions.

Answer:

Exothermic Reactions	Endothermic Reactions
Reaction between potassium permanganate and glycerine.	Decomposition of potassium permanganate
Reaction between magnesium and hydrochloric acid.	Reaction between ammonium chloride and barium hydroxide
Burning of Hydrogen in Air	Dissolution of Salts in Water
Reaction of Water with Quicklime	Process of heating Limestone to produce Quicklime

The reactions in which heat energy is liberated or absorbed are known as thermochemical reactions.

Question 33.
Which reaction is represented by the illustration

Answer:
Photosynthesis

a. What are the reactants and the products here?
Answer:
Reactant: Carbon dioxide and water
Product: Glucose and oxygen

b. Which form of energy is absorbed in photosynthesis
Answer:
Light energy

In photosynthesis, light energy is converted into chemical energy.

Question 34.
a. Do you know any reactions that liberate light energy?
Answer:
Combustion reactions: For example, burning of wood, candles, or fuels like natural gas, where heat and light are produced.
Bioluminescence: Chemical reactions occurring in living organisms that produce light (like fireflies).

b. How do fireflies produce light?
Answer:
The chemical luciferin (in fireflies) absorbs ultraviolet rays.

• This process is aided by the enzyme luciferase, which is also present in fireflies.
• As a result, visible light is emitted.
• This phenomenon is known as bioluminescence.
• Fireflies can control the amount of oxygen entering their body.
• This control allows them to regulate the intensity of light produced.
• Some species of marine organisms and worms also exhibit bioluminescence.

Question 35.
Some medicines are kept in brown-coloured bottles. What could be the reason?
Answer:
Some medicines decompose and change into other substances in the presence of light. Therefore, they are stored in brown bottles. Brown bottles do not allow light to pass through.

Question 36.
Silver nitrate is not stored in transparent bottles. Why?
Answer:
Silver nitrate is a compound with very low stability. It decomposes in the presence of light. Therefore, silver nitrate is not stored in transparent bottles.

Question 37.
Look at the figures given.

They are known as dry cells.

a. What is their use?
Answer:
Dry cells are used to convert chemical energy into electrical energy.

b. What are the parts of a dry cell?
Answer:

Electricity is produced because of chemical reactions that take place in a dry cell

In a dry cell chemical energy is conreated into electricl energy.

EXPERIMENT
Take some concentrated salt solution (sodium chloride) in a beaker. Add three or four drops of phenolphthalein into it. Dip the ends of copper wires connected to both the terminals of a battery into the solution.

a. What is your observation?
Answer:
When electricity is passed through, the solution turns pink

b. Which compound’s presence is indicated by pink colour?
Answer:
When sodium chloride undergoes dissociation, sodium hydroxide is formed as one of the products. This turns the solution pink.

c. Which form of energy is responsible for this reaction?
Answer:
Electrical energy

ELECTROLYSIS
The process of dissociation of a substance by absorbing electrical energy is known as electrolysis.
If electricity is passed through water containing a small amount of acid, it dissociates into hydrogen and oxygen.
Water → Hydrogen + Oxygen
Water dissociates by absorbing electrical energy.
Hence, this process is electrolysis.
Many such reactions take place by absorbing electricity.

ELECTROPLATING
Coating a metal with another metal using electricity is known as electroplating.

EXPERIMENT
Let’s coat copper on an iron bangle

a. Which solution is taken in the beaker?
Answer:
Copper sulphate solution

b. To which terminal of the battery is the copper plate connected?
Answer:
Positive

c. What about the bangle?
Answer:
Negative terminal of the battery

Question 38.
What all things should be taken care of during electroplating?
Answer:

• The metal that is to be plated should be connected to the positive terminal of the battery.
• The object on which the plating is to be done should be connected to the negative terminal of the battery.
• A salt solution containing ions of the metal being plated should be used as the electrolyte

SUITABLE SOLUTIONS FOR ELECTROPLATING EACH METAL:

Metal	Suitable solutions
Copper	Copper sulphate solution
Silver	A mixture of sodium cyanide and silver cyanide solutions
Gold	A mixture of sodium cyanide and gold cyanide solutions

Question 39.
Which metal plate should be connected to the positive terminal of the battery if silver is to be coated instead of copper?
Answer:
The plate of the metal to be plated should be connected to the positive terminal of the battery.

Question 40.
Which energy has caused the LED to glow?
Answer:
Electrical energy

Question 41.
Which is the source of this electrical energy?
Answer:
Here, the acid in the lemons reacts with metals to produce electricity.

If electrical energy is absorbed or produced during a chemical reaction, it is known as an electrochemical reaction.

Different forms of energy are absorbed or liberated in every chemical reaction. Reactions are known by the major form of energy involved in that reaction.

Chemical Reaction	Main Energy Change
Burning of substances	Liberates heat
Decomposition of substances on heating	Absorb heat
Bioluminescence	Liberates Light
A cell made of lemon.	Liberates electrical energy
Electrolysis of Sodium Chloride solution	Absorbs electrical energy

Question 42.
You have understood about the state of the matter and the changes they undergo. Among these, there are changes that are beneficial to human life and those that are not. Discuss in class how the changes in matter influence human life and prepare a note.
Answer:
Hints: –

• Living organisms produce the starch they need through photosynthesis. Photosynthesis also helps to maintain a stable level of oxygen in the atmosphere
• Through the combustion of fuels, thermal energy can be produced. This chemical change is very important for domestic needs and for the functioning of vehicles. The combustion of substances can also cause pollution.
• Electricity is generated through chemical reactions in electrochemical cells. The disposal of electrochemical cells causes environmental problems.
• The biodegradation of substances is a chemical reaction. It is helpful for environmental cleaning and waste disposal
• Chemical reactions in factories help in producing necessary products. By-products from factories can lead to pollution.

Class 8 Basic Science Chapter 4 Question Answer Extended Activities

Question 1.
Collect a little aluminium powder and iodine powder from the science lab. Mix them well. Add two or three drops of water to this mixture. Write the observations.
Answer:
Initially, nothing much happens when the powders are just mixed.

• Upon adding two or three drops of water, a vigorous reaction starts.
• Heat will be generated, and the mixture will become warm or even hot.
• Purple colored fumes (iodine vapour) will be seen rising from the mixture.
• A loud crackling or popping sound might be heard.
• The mixture might glow or sparkle briefly due to the intensity of the reaction.
• After the reaction subsides, a white or greyish solid (aluminium iodide) will be left behind.

Question 2.
Make a heap of ammonium dichromate powder on a tile. Make a small pit in it and insert the chemicals collected from matchsticks and ignite it. Record the changes you see.
Answer:
When the matchstick chemicals are ht in the pit, the orange powder starts to burn and glow.

• Suddenly, the heap of orange powder starts to grow bigger and pushes upwards, just like a volcano erupting!
• Bright orange sparks fly out from the top of the “volcano.”
• Instead of orange powder, a fluffy, dark green-black powder comes out and piles up around the base of the volcano.
• You can see smoke or steam rising from the reaction.
• The reaction continues for a while, making more and more of the green-black powder, and the “volcano” keeps growing taller.
• The entire process produces heat and light.

Chemistry of Changes Class 8 Notes

Class 8 Basic Science Chemistry of Changes Notes Kerala Syllabus

• Matter is anything that has mass and occupies space (volume).
• Properties of Matter:
  Mass: All matter has mass, (e.g., a big stone has more mass than a small one; air also has mass).
• Volume: All matter occupies space, (e.g., a stone displaces water; air inside a glass prevents water from entering).
• Matter mainly exists in three states:
  Solid:
  • Definite shape and definite volume.
  • Particles are very close and tightly packed.
  • Strong force of attraction between particles.
  • Particles vibrate in fixed positions (very low speed of movement).
  • Very low energy of particles.
    Liquid:
  • Definite volume but no definite shape (takes the shape of the container).
  • Particles are close but can move past each other.
  • Less attraction between particles than solids.
  • Higher speed of movement than solids.
  • Higher energy of particles than solids.
    Gas:
  • No definite shape and no definite volume (fills the entire container).
  • Particles are very far apart.
  • Very weak force of attraction between particles.
  • Particles move very fast and randomly (very high speed of movement).
  • Very high energy of particles.
• Changes in Matter
  • When matter changes from one state to another (e.g., solid to liquid, liquid to gas), it’s called a change of state
  • Role of Heat Energy:
    Heating (Absorption of Heat): Increases particle distance, speed, and energy.
    (Solid → Liquid → Gas).
    Cooling (Liberation/Release of Heat): Decreases particle distance, speed, and energy.
    (Gas → Liquid → Solid).
  • Sublimation: Some solids (like camphor, naphthalene) directly change into gas upon heating, without becoming liquid.
• Different Types of Changes
  Changes can be classified in various ways:
  • Physical Change: A change in appearance or form, but no new substance is formed. It’s often reversible. Examples: Melting wax, forming ice, dissolving salt in water, and melting ice.
  • Chemical Change: A process where new substances are formed with different properties. It’s usually irreversible. Examples: Burning paper/caridle/firewood, curdling of milk, rusting of iron,
  • Slow Changes and Fast Changes:
    • Slow: Rusting of iron, ripening of fruit, germination of seeds, milk turning to curd.
    • Fast: Burning petrol, explosion of firecrackers, lighting a gas stove.
• Natural Changes and Man-made Changes:
  • Natural: Ripening of bananas, rusting.
  • Man-made: Sculpting stone, burning fuel
• All chemical changes involve an energy change. Energy is either absorbed or released.
• Thermochemical Reactions: Reactions primarily involving heat energy.
  • Exothermic Reactions: Release heat energy (e.g., burning fuels, quicklime reacting With water, magnesium reacting with HCl). You’ll feel the container get warm/hot.
  • Endothermic Reactions: Absorb heat energy (e.g., decomposition of potassium permanga-nate by heating, ammonium chloride reacting with barium hydroxide). You’ll feel the container get cold.
• Photochemical Reactions: Reactions initiated or driven by light energy.
  • Absorb Light: Photosynthesis (plants convert CO2 and water using sunlight), decomposition of silver chloride (turns black in light).
  • Release Light: Bioluminescence (fireflies glowing), Chemiluminescence (glow sticks), combustion
    reactions (burning wood, candles).
  • Storing light-sensitive medicines/chemicals in brown bottles to prevent decomposition by light.
• Electrochemical Reactions: Reactions involving the conversion between chemical energy and electrical energy.
  • Release Electricity (Chemical to Electrical): Batteries/cells (e.g., dry cell, lemon battery).
  • Absorb Electricity (Electrical to Chemical): Electrolysis (breaking down substances using electricity, like water into hydrogen and oxygen).
  • Electroplating (coating one metal with another using electricity).
• Electroplating Setup:
  • The Object to be plated is connected to the negative terminal (cathode)
  • The plating metal is Connected to the positive terminal (anode)
  • The electrolyte contains ions of the plating metal.
• Changes in matter, both physical and chemical, significantly influence human life.
  Beneficial Changes:
  • Photosynthesis (produces food and oxygen).
  • Combustion of fuels (provides energy for homes, transport, industries).
  • Production of chemicals (fertilisers, medicines).
  • Biodegradation (waste disposal, environmental cleaning).
  • Electrochemical cells (batteries for devices).
    Harmful Changes
  • Pollution from fuel combustion.
  • Environmental problems from electro-chemical cell disposal.
  • Harmful effects of excessive/unscientific use of pesticides.
  • Pollution from industrial by-products.

INTRODUCTION

Many chemical reactions are happening around us. Changes from one form of matter to another can be categorised into various classifications, including physical and chemical changes, complex and relatively simple changes, natural and man-made changes, and permanent and temporary changes. Chemical changes are those that produce new substances. When chemical changes occur, energy is released or absorbed.

All substances around us exist in various forms of matter. Solid, liquid, and gas are the main states of matter. Matter can be changed from one state to another. This is called a phase transition. All changes occurring in nature have an impact on human life. This unit will cover these topics.

PHYSICAL CHANGE AND CHEMICAL CHANGE
Physical Change: A physical change is a process where the form or appearance of a substance changes, but its chemical composition remains the same. No new substances are formed.

Chemical Change: A chemical change is a process where a substance is converted into a different substance (or substances). This means new molecules are formed.

CHEMICAL CHANGES AND ENERGY CHANGE
EXPERIMENT:
Place some potassium permanganate crystals on a tile and pour glycerin in the middle. Record your observation.
Observation: An Intense reaction is taking place. Gases are being released. After a short while, the mixture ignites.

THERMOCHEMICAL REACTIONS
EXPERIMENT:
Take a piece of magnesium in a test tube and add diluted hydrochloric acid into it.
a. What do you observe?
Answer:
A vigorous reaction takes place with the release of a gas

b. How will you identify the gas formed here?
Answer:
If a burning matchstick is brought near the mouth of the test tube, the gas bums with a pop sound.

c. Which is this gas?
Answer:
When magnesium reacts with diluted hydrochloric acid, hydrogen gas is formed.

d. Touch the bottom of the test tube. What do you feel?
Answer:
As a result of the chemical reaction, heat is also produced along with hydrogen. Therefore, you will feel the bottom of the test tube become warm or hot.

e. What are the reactants of this reaction?
Answer:
Magnesium (Mg) and Hydrochloric Acid (HCl).

f. What are the products?
Answer:
Magnesium Chloride (MgCl₂) and Hydrogen gas (H₂).

Magnesium + Hydrochloric Acid (Dilute) → Magnesium Chloride + Hydrogen + Heat

EXPERIMENT:
Take quicklime in a steel cup. Add some water to it. Touch the cup after some time.
a. What do you feel?
Answer:
The steel cup becomes hot or warm.

b. What is the reason?
Answer:
The chemical reaction between quicklime (calcium oxide) and water releases a significant amount of heat. This type of reaction is called an exothermic reaction.
Quicklime + water → slaked lime + Heat

If heat is liberated as a result of a chemical reaction, such reactions are known as exothermic reactions.

EXPERIMENT:
Take some potassium permanganate in a test tube and heat it. Hold a burning incense stick near the mouth of this test tube.

a. What do you observe?
Answer:
An Incense stick will flare up or glow more brightly

b. Which gas helps flaring the incense stick?
Answer:
Oxygen

c. Which form of energy is used to decompose potassium permanganate?
Answer:
Heat energy (or Thermal energy)

EXPERIMENT:
Take some ammonium chloride in a watch glass, add some barium hydroxide into it and mix well with a glass rod. Touch the bottom of the watch glass.

a. What do you feel?
Answer:
The bottom of the watch glass becomes cold.

b. Is heat energy absorbed or liberated here?
Answer:
Heat energy is absorbed here.

If heat energy is absorbed during a chemical reaction, it is known as an endothermic reaction.

PHOTOCHEMICAL REACTIONS
The reactions in which light energy is absorbed or liberated are known as photochemical reactions.

EXPERIMENT
Take some silver nitrate solution in a watch glass and add sodium chloride solution to it. Dip two pieces of cotton in the product formed. Cover one of them with black paper and keep the other one open. Keep them aside for some time.

a. Record your observations.
Answer:
After some time, the piece of cotton dipped in the product (AgCl) and kept open to light will turn grey or blackish.
The piece of cotton dipped in the product (AgCl) and covered with black paper will remain white or show very little change in colour.

b. Which form of energy is responsible for the colour change
Answer:
Light energy.

c. Explain why a piece of cotton dipped in silver chloride turns black when exposed to light but remains white when covered.
Answer:
The reactants, silver nitrate and sodium chloride, react to form silver chloride. This silver chloride decomposes by absorbing light to form silver. This is the reason for the blackening of the cotton, which is kept open.
Silver nitrate + Sodium chloride → Silver chloride + Sodium nitrate
Silver chloride → Silver + chlorine

BATTERY MADE OF LEMONS
Arrange zinc and copper nails on lemons as shown in the figure. Connect them with copper wire. Then connect this arrangement to an LED.

Students often refer to Kerala State Syllabus SCERT Class 6 Maths Solutions and Class 6 Maths Chapter 5 Decimal Forms Questions and Answers Notes Pdf to clear their doubts.

SCERT Class 6 Maths Chapter 5 Solutions Decimal Forms

Class 6 Kerala Syllabus Maths Solutions Chapter 5 Decimal Forms Questions and Answers

Decimal Forms Class 6 Questions and Answers Kerala Syllabus

Decimal Places (Page No. 69)

Question 1.
Split the numbers below according to place value:
(i) 4.5
(ii) 4.57
(iii) 4.572
(iv) 45.72
(v) 457.2
Answer:

Textbook Page No. 71

Question 1.
Now try to write 4 kilograms and 55 grams as kilograms in decimal form.
Answer:
4 kilograms 55 grams
55 grams means \(\frac {55}{1000}\) kilograms.
So, 4 kilograms 55 grams = 4\(\frac {55}{1000}\) kilograms
Splitting 4\(\frac {55}{1000}\) according to place value

So we can write the decimal form of 4\(\frac {55}{1000}\) as 4.055

Question 2.
Convert the measures below into the measures specified, using fractions and decimal forms.

Answer:

Decimals and Fractions (Page No. 74)

Question 1.
The decimal form of some numbers is given below. Write each of them as a fraction with a denominator of 10, 100, or 1000.
(i) 3.7
(ii) 3.07
(iii) 30.7
(iv) 3.72
(v) 37.2
(vi) 3.072
(vii) 30.72
Answer:
(i) \(\frac {37}{10}\)
(ii) \(\frac {307}{100}\)
(iii) \(\frac {307}{10}\)
(iv) \(\frac {372}{100}\)
(v) \(\frac {372}{10}\)
(vi) \(\frac {3072}{1000}\)
(vii) \(\frac {3072}{100}\)

Question 2.
Write the decimal form of the fractions given below.
(i) \(\frac {51}{100}\)
(ii) \(\frac {513}{10}\)
(iii) \(\frac {513}{100}\)
(iv) \(\frac {513}{1000}\)
(v) \(\frac {5130}{1000}\)
Answer:
(i) 5.1
(ii) 51.3
(iii) 5.13
(iv) 0.513
(v) 5.13

Addition and Subtraction (Page No. 79)

Question 1.
Anu made an 8.5 metre long festoon and Sarah made a 7.8 metre long one to decorate their classroom for the school anniversary. What is the total length of the festoon they made?
Answer:
Length of the festoon Anu made = 8.5 metres
Length of the Festoon Sarah made = 7.8 metres
Removing the measures and converting into a fraction
8.5 = \(\frac {85}{10}\)
7.8 = \(\frac {78}{10}\)
Adding the fraction
\(\frac{85}{10}+\frac{78}{10}=\frac{163}{10}\)
Converting to decimals
\(\frac {163}{10}\) = 16.3
Total length of the festoon = 16.3 metres

Question 2.
Amal needs 2.25 metres of cloth and Sagar, 1.85 metres for a school uniform. How many metres of cloth in all?
Answer:
Length of the cloth Amal needs for the school uniform = 2.25 metres
Length of the cloth Sagar needs for the school uniform = 1.85 metres
Removing measures and converting to fractions
2.25 = \(\frac {225}{100}\)
1.85 = \(\frac {185}{100}\)
Adding these fractions
\(\frac{225}{100}+\frac{185}{100}=\frac{200+100+25+85}{100}=\frac{410}{100}\)
Converting this to decimals \(\frac {410}{100}\) = 4.1
Total length of cloth in all is 4.1 metres.

Question 3.
A tin weighs 2.85 kilograms, and it is filled with 12.5 kilograms of rice. What is the total weight?
Answer:
Weight of the tin = 2.85 kilograms
Amount of rice filled in the tin = 12.5 kilograms
Removing measures and converting to fractions
2.85 = \(\frac {285}{100}\)
12.5 = \(\frac {125}{10}\)
Adding these fractions
\(\frac{285}{100}+\frac{125}{10}\)
To add these changing \(\frac {125}{10}\) to a form with denominator
\(\frac{125 \times 10}{10 \times 10}=\frac{1250}{100}\)
Adding these fractions,
\(\frac{1250}{100}+\frac{285}{100}\)
1000 + 200 + 250 + 85 = 1200 + 335 = 1535
\(\frac{1250}{100}+\frac{285}{100}=\frac{1535}{100}\)
Converting the fractions to decimals
\(\frac {1535}{100}\) = 15.35
Total weight = 15.35 kilograms

Question 4.
Bakul walks 2.25 kilometres in the morning and 1.5 kilometres in the evening every day. What is the total distance she walks each day?
Answer:
Distance Bakul walks in the morning = 2.25 kilometres
Distance Bakul walks in the evening = 1.5 kilometres
Total distance she walks each day = 2.25 kilometres + 1.5 kilometres
Removing measures and converting to fractions
2.25 = \(\frac {225}{100}\)
1.5 = \(\frac {15}{10}\)
To add these, change \(\frac {15}{10}\) to a form with denominator 100
\(\frac{15 \times 10}{10 \times 10}=\frac{150}{100}\)
Adding the fractions
\(\frac{225}{100}+\frac{150}{100}\)
200 + 100 + 25 + 50 = 375
\(\frac{225}{100}+\frac{150}{100}=\frac{375}{100}\)
Converting the fractions to decimals
\(\frac {375}{100}\) = 3.75
Total distance she walks each day = 3.75 kilometres

Question 5.
Two small bottles contain 0.850 litres and 0.375 litres of honey. If both the bottles are emptied into a large bottle, how much honey does it contain?
Answer:
Amount of honey in the first bottle = 0.850 litres
Amount of honey in the second bottle = 0.375 litres
Amount of honey in the large bottle = 0.850 litre + 0.375 litre
Removing measures and making into fractions
0.375 = \(\frac {375}{1000}\)
0.850 = \(\frac {850}{1000}\)
Adding these \(\frac{375}{1000}+\frac{850}{1000}\)
375 + 850 = 300 + 800 + 75 + 50 = 1225
\(\frac{375}{1000}+\frac{850}{1000}=\frac{1225}{1000}\)
Converting the fractions into decimals
\(\frac {1225}{1000}\) = 1.225
Amount of honey in the large bottle = 1.225 litres.

Textbook Page No. 82

Question 1.
From a rod 14.7 metres long, a piece 7.75 metres long is cut off. What is the length of the remaining piece?
Answer:
Length of the long rod = 14.7 metres
Length of the piece cut off from the long rod = 7.75 metres
Length of the remaining piece = 14.7 metre – 7.75 metres
Changing into fractions
14.7 = \(\frac {147}{10}\)
7.75 = \(\frac {775}{100}\)
To subtract change \(\frac {147}{10}\) to a form with denominator 100
\(\frac{147 \times 10}{10 \times 10}=\frac{1470}{100}\)
Subtracting \(\frac{1470}{100}-\frac{775}{100}=\frac{695}{100}\)
Changing back to decimals
\(\frac {695}{100}\) = 6.95
Length of the remaining piece = 6.95 metres.

Question 2.
There were 38.7 kilograms of rice in a sack, and 12.350 kilograms of this were used up. How much rice remains in the sack?
Answer:
Amount of rice in the sack = 38.7 kilograms
Amount of rice used up = 12.350 kilograms
Amount of rice remaining in the sack = 38.7 kilograms – 12.350 kilograms
38.7 = \(\frac {387}{10}\)
12.350 = \(\frac {12350}{1000}\)
\(\frac{387}{10}-\frac{12350}{1000}\)
\(\frac{387 \times 100}{10 \times 100}=\frac{38700}{1000}\)
Subtracting \(\frac{38700}{1000}-\frac{12350}{1000}=\frac{26350}{1000}\)
Changing back to decimals
\(\frac {26350}{1000}\) = 26.35
Amount of rice remaining in the sack = 26.35 kilograms

Question 3.
The perimeter of a rectangle is 24 centimetres and the length of one side is 6.4 centimetres. What is the length of the other side?
Answer:
Perimeter of rectangle = 2(length + breadth) = 24 centimetres
Length of one side = 6.4 centimetres
Length of the other side = 12 – 6.4 = 5.6 centimetres

Question 4.
There were 2.50 litres of oil in a bottle, and 0.475 litres of this were used for cooking. How much oil is left in the bottle?
Answer:
Amount of oil in the bottle = 2.50 litres
Amount of oil used for cooking = 0.475 litres
Amount of oil left in the bottle = 2.50 litres – 0.475 litres
2.50 = \(\frac {250}{100}\)
0.475 = \(\frac {475}{1000}\)
\(\frac{250}{100}-\frac{475}{1000}\)
\(\frac{250 \times 10}{100 \times 10}=\frac{2500}{1000}\)
Subtracting \(\frac{2500}{1000}-\frac{475}{1000}=\frac{2025}{1000}\)
Amount of oil remaining = 2.025 litres

Question 5.
What number must we add to 14.32 to get 16.43?
Answer:
Number to be added to 14.32 to get 16.43 = 16.43 – 14.32
16.43 = \(\frac {1643}{100}\)
14.32 = \(\frac {1432}{100}\)
Subtracting \(\frac{1643}{100}-\frac{1432}{100}=\frac{211}{100}\)
Converting back to decimals
\(\frac {211}{100}\) = 2.11

Class 6 Maths Chapter 5 Kerala Syllabus Decimal Forms Questions and Answers

Class 6 Maths Decimal Forms Questions and Answers

Question 1.
Split the numbers below according to place value.
(i) 3.6
(ii) 3.64
(iii) 3.641
(iv) 36.41
(v) 364.1
Answer:

Question 2.
Convert the following measures into the specified forms, using both fractions and decimal forms.

Answer:

Question 3.
The decimal form of some numbers is given below. Write each of them as a fraction with a denominator of 10, 100, or 1000.
(i) 4.2
(ii) 4.02
(iii) 40.2
(iv) 4.25
(v) 42.5
(vi) 4.025
(vii) 40.25
Answer:
(i) \(\frac {42}{10}\)
(ii) \(\frac {402}{100}\)
(iii) \(\frac {402}{10}\)
(iv) \(\frac {425}{100}\)
(v) \(\frac {4025}{1000}\)
(vi) \(\frac {4025}{100}\)

Question 4.
Write the decimal form of the fractions given below.
(i) \(\frac {9}{10}\)
(ii) \(\frac {47}{100}\)
(iii) \(\frac {381}{1000}\)
(iv) \(\frac {15}{10}\)
(v) \(\frac {245}{100}\)
(vi) \(\frac {7}{100}\)
(vii) \(\frac {82}{1000}\)
(viii) \(\frac {3456}{1000}\)
Answer:
(i) 0.9
(ii) 0.47
(iii) 0.381
(iv) 1.5
(v) 2.45
(vi) 0.07
(vii) 0.082
(viii) 3.456

Question 5.
John ran a distance of 4.25 kilometres and then walked another 2.5 kilometres. What is the total distance he covered?
Answer:
Distance John ran = 4.25 kilometres
Distance he walked = 2.5 kilometres
Total distance he covered = 4.25 kilometres + 2.5 kilometres
Converting into fractions
4.25 = \(\frac {425}{100}\)
25 = \(\frac{25}{10}=\frac{25 \times 10}{10 \times 10}=\frac{250}{100}\)
Adding \(\frac{425}{100}+\frac{250}{100}=\frac{675}{100}\)
Converting to decimals
\(\frac {675}{100}\) = 6.75
Total distance John covered = 6.75 kilometres

Question 6.
A baker has two bags of flour, one with 1.75 kilograms of flour and the other with 2.5 kilograms. If the baker combines all the flour into a single container, what is the total weight of the flour in the container?
Answer:
Total weight of the flour in the container = Amount of flour in Bag 1 + Amount of flour in Bag 2 = 1.75 kilograms + 2.5 kilograms
1.75 = \(\frac {175}{100}\)
2.5 = \(\frac{25}{10}=\frac{25 \times 10}{10 \times 10}=\frac{250}{100}\)
Adding \(\frac{175}{100}+\frac{250}{100}=\frac{425}{100}\)
Converting into decimals
\(\frac {425}{100}\) = 4.25
Total weight of the flour in the container = 4.25 kilograms

Question 7.
A ribbon was 15.8 metres long. If a piece measuring 4.25 metres was cut from it, how much ribbon is left?
Answer:
Length of the ribbon = 15.8 metres
Length of the piece cut off from the ribbon = 4.25 metres
Length of the ribbon left = 15.8 metres – 4.25 metres
15.8 = \(\frac{158}{10}=\frac{158 \times 10}{10 \times 10}=\frac{1580}{100}\)
4.25 = \(\frac {425}{100}\)
Subtracting \(\frac{1580}{100}-\frac{425}{100}=\frac{1155}{100}\)
Converting back to decimals
\(\frac {1155}{100}\) = 11.55
Length of the ribbon left = 11.55 metres

Question 8.
A water tank holds 50.5 litres of water. If 25.5 litres are used for gardening, how much water is left in the tank?
Answer:
Amount of water left in the tank = Amount of water that the water tank can hold – Amount of water used for gardening
50.5 = \(\frac {505}{10}\)
255 = \(\frac {255}{10}\)
Subtracting \(\frac{505}{10}-\frac{255}{10}=\frac{250}{10}\)
Converting to decimals
\(\frac {250}{10}\) = 2.5

Question 9.
A carpenter uses a 2.75-metre board and a 1.5-metre board for a project. What is the total length of the wood used?
Answer:
Total length of the wood used = 2.75 metre + 1.5 metre
2.75 = \(\frac {275}{100}\)
1.5 = \(\frac{15}{10}=\frac{15 \times 10}{10 \times 10}=\frac{150}{100}\)
Adding \(\frac{275}{100}+\frac{150}{100}=\frac{425}{100}\)
Converting to decimals
\(\frac {425}{100}\) = 4.25
Total length of the wood used = 4.25 metres

Question 10.
A plant is 15.6 centimetres tall. How many more centimetres must it grow to reach a height of 20.1 centimetres?
Answer:
Height of the plant = 15.6 centimetres
Target height = 20.1 centimetres
Height the plant must grow = 20.1 centimetres – 15.6 centimetres
20.1 = \(\frac {201}{10}\)
15.6 = \(\frac {156}{10}\)
Subtracting \(\frac{201}{10}-\frac{156}{10}=\frac{45}{10}\)
Converting to decimals
\(\frac {45}{10}\) = 4.5
The plant must grow 4.5 centimetres to reach the target height.

Class 6 Maths Chapter 5 Notes Kerala Syllabus Decimal Forms

→ In the decimal form of a number, the dot (decimal point) separates the whole number part and the fractional part.

→ Digits to the left of the decimal point represent ones, tens, hundreds, and so on;

→ The digits to the right represent tenths, hundredths, thousandths, and so on.

→ Decimals allow us to represent quantities that are not whole numbers with greater precision, making them essential for measurements, money, and other real-world applications.

→ To convert a measurement from centimetres to metres in decimal form, divide the number of centimetres by 100. This is equivalent to moving the decimal point two places to the left.

→ If you have a combination of metres and centimetres, first convert the centimetres to metres as a decimal and then add them to the whole number of metres.

→ To convert a measurement from centimetres to millimetres, multiply the number by 10.

→ To convert from millimetres to centimetres, divide the number by 10.

→ To add decimal numbers representing measurements (like 4.3 cm and 2.5 cm), align the decimal points and add them directly.

→ Alternatively, you can convert the measurements to a smaller unit (like millimetres) and complete the addition, then convert the result back to the original unit.

→ To subtract a decimal from another (like subtracting 3.2 cm from 8.5 cm), you can convert both decimals to fractions with a common denominator, subtract them, and then convert the result back into a decimal.

This chapter comprehensively covers the representation and manipulation of numbers beyond whole units. Key topics include understanding decimal places to denote fractional parts, establishing the crucial relationship and conversion techniques between decimals and fractions, and mastering the fundamental operations of addition and subtraction of decimal numbers to build foundational arithmetic skills.

Decimal Places
The length of a pencil can be said in different ways:

• 5 centimetres 7 millimetres
• 5\(\frac {7}{10}\) centimetres
• 5.7 centimetres

We can write other measures also like this:
5\(\frac {7}{10}\) litres = 5.7 litres
5\(\frac {7}{10}\) kilograms = 5.7 kilograms

We can drop all references to measures and simply say that 5.7 is the decimal form of the number 5\(\frac {7}{10}\).
5\(\frac {7}{10}\) = 5.7
Similarly, 4.29 is the decimal form of 4\(\frac {29}{100}\)
4\(\frac {29}{100}\) = 4.29

We write natural numbers using ones, tens, hundreds, and so on.
For example: 247 = 2 hundreds + 4 tens + 7 ones
Splitting 247.3
Split it as the sum of a whole number and a fraction.
247.3 = 247\(\frac {3}{10}\) = 247 + \(\frac {3}{10}\)
First, we split 247.3 as the sum of a whole number and a fraction, as
247.3 = 247\(\frac {3}{10}\) = 247 + \(\frac {3}{10}\)
The \(\frac {3}{10}\) here can be written as
\(\frac{3}{10}=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}\)
That is, 3 tenths. So, we can write 247.3 in terms of hundreds, tens, ones, and tenths:
247.3 = 2 hundreds + 4 tens + 7 ones + 3 tenths

Splitting 247.39
First, we write it as
247.39 = 247\(\frac {39}{100}\)= 247 + \(\frac {39}{100}\)
Then, we can split \(\frac {39}{100}\) as
\(\frac{39}{100}=\frac{30+9}{100}=\frac{30}{100}+\frac{9}{100}=\frac{3}{10}+\frac{9}{100}\)
The \(\frac {3}{10}\) here is 3 tenths: and \(\frac {9}{100}\) is 9 hundredths.
So 247.39 = 2 hundreds + 4 tens + 7 ones + 3 tenths + 9 hundredths

In the decimal form of a number, the dot separates the whole number part and the fractional part. Digits to the left of the dot show the multiples of ones, tens, hundreds, and so on; the digits to the right show the multiples of tenths, hundredths, thousandths, and so on.
For example, the two numbers used in the above examples can be split according to place value like this:

Question 1.
What is the decimal form of 23 metres 40 centimetres?
Answer:
Method 1
23 metres 40 centimetres = 23\(\frac {40}{100}\) metres = 23.40 metres
Taking only the numbers, we have
23\(\frac {40}{100}\) = 23.40
We can write the \(\frac {40}{100}\) here as
\(\frac{40}{100}=\frac{4}{10}\)
So, we get 23\(\frac {40}{100}\) = 23\(\frac {4}{10}\) = 23.4
This means 23.40 = 23.4

Method 2
Using place value

Thus, we can write 23 metres and 40 centimetres in two different ways:
23 metres 40 centimetres = 23.40 metres
23 metres 40 centimetres = 23.4 metres

Question 2.
What is the decimal form of 23 metres 4 centimetres?
Answer:
4 centimetres = \(\frac {4}{100}\) metre.
23 metres 4 centimetres =23\(\frac {4}{100}\) metres
Split 23\(\frac {4}{100}\) according to place value:
23\(\frac {4}{100}\) = 2 tens + 3 ones + 4 hundredths

The decimal form of 23\(\frac {4}{100}\) = 23.04

Question 3.
What is the decimal form of 23 metres and 4 millimetres?
Answer:
4 millimetres means \(\frac {4}{1000}\) metres.
So 23 metres 4 millimetres = 23\(\frac {4}{1000}\) metres
Split 23\(\frac {4}{1000}\) according to place value.

So, we can write the decimal form of 23\(\frac {4}{1000}\) as
23\(\frac {4}{1000}\) = 23.004

Converting Centimetres to a Decimal Form of Metres
To convert centimetres to a decimal form of metres, first, write the number of metres as the whole number part of your decimal.
Next, express the number of centimetres as a fraction of a metre. Since there are 100 centimetres in 1 metre, the denominator of your fraction will be 100. For example, 40 centimetres would be written as \(\frac {40}{100}\) metres.
Combine the whole number and the fraction to create a mixed number, such as 23\(\frac {40}{100}\).
To get the decimal form, divide the numerator of your fraction by 100. This is the same as moving the decimal point two places to the left. So, \(\frac {40}{100}\) becomes 0.40.
Finally, add the decimal to the whole number.
For example, 23 + 0.40 = 23.40.
The result is the length in meters.

Decimals and Fractions
Conversion of decimals into fractions
Start with the decimal number you want to convert.

Example: 7.3 centimetres
Write this in millimetres
7 centimetres = 70 millimetres
To convert \(\frac {3}{10}\) centimetres into millimetres:
\(\frac {3}{10}\) is three \(\frac {1}{10}\)
\(\frac {3}{10}\) centimetres = 3 millimetres
7.3 centimetres = 70 millimetres + 3 millimetres

Converting 73 millimetres into centimetres:
Divide it by 10
73 millimetres = \(\frac {73}{10}\) centimetres
Removing measure and writing as just numbers 7.3 = \(\frac {73}{10}\)

Question 4.
How do we write 7.31 metres as a fraction?
Answer:
Write it as a whole number and a fraction
7.31 metres = 7\(\frac {31}{100}\) metres
7 metres = 700 centimetres
\(\frac {31}{100}\) metres = 31 centimetres
7.31 metres = 700 centimetres + 31 centimetres = 731 centimeters
Converting this into metres
731 centimetres = \(\frac {731}{100}\) metres
7.31 metres = \(\frac {731}{100}\) metres

Question 5.
Convert 7.319 litres as a fraction.
Answer:
7.319 litres = 7\(\frac {319}{1000}\) litres
7 litres = 7000 millilitres
\(\frac {319}{1000}\) litres = 319 millilitres
7.319 litres = 7319 millilitres
Converting back to litres
7319 millilitres = \(\frac {7319}{1000}\) litres
7.319 litres = \(\frac {7319}{1000}\) litres

Converting 12.03 to a Fraction

• Step 1: Count the digits after the decimal point in 12.03. There are two digits (0 and 3).
• Step 2: The denominator is 100 because there are two digits after the decimal.
• Step 3: Remove the decimal point from 12.03 to get the numerator, which is 1203.
• Step 4: The final fraction is \(\frac {1203}{100}\).

Question 6.
What is the decimal form of \(\frac {1203}{1000}\)?
Answer:
Looking at the denominator, we can say there will be three digits after the decimal point.
\(\frac {1203}{1000}\) = 1.203

Addition and Subtraction

Addition of Decimal Numbers
A line 4.3 centimetres long was drawn and then extended by another 2.5 centimetres:

To find the total length of the line we have to add 4.3 centimetres and 2.5 centimetres

Method 1
Convert these to centimetres and millimetres.
4.3 centimetres = 4 centimetres 3 millimetres
2.5 centimetres = 2 centimetres 5 millimetres
And add the centimetres and millimetres separately.
4 centimetres + 2 centimetres = 6 centimetres
3 millimetres + 5 millimetres = 8 millimetres
The length of the line is 6 centimetres, 8 millimetres
Convert back to centimetres.
6 centimetres 8 millimetres = \(\frac {68}{10}\) centimetres = 6.8 centimetres

Method 2
Write the lengths in millimetres.
4.3 centimetres = 43 millimetres
2.5 centimetres = 25 millimetres
Add 43 and 25
43 + 25 = 40 + 20 + 3 + 5 = 68
Thus, the length of the line is 68 millimetres
Write as centimetres in decimal form.
68 millimetres = 6 centimetres 8 millimetres = 6.8 centimetres

Method 3
Remove the measures and write the numbers as fractions.
4.3 = \(\frac {43}{10}\)
2.5 = \(\frac {25}{10}\)
And these fractions we can add like this:
\(\frac{43}{10}+\frac{25}{10}=\frac{43+25}{10}=\frac{68}{10}\)
Write the fraction as a decimal number
\(\frac {68}{10}\) = 6.8
The length of the line is 6.8 centimetres.

Question 7.
Add 4.3 centimetres and 2.8 centimetres.
Answer:
Changing the lengths into millimetres
4.3 centimetres = 43 millimetres
2.8 centimetres = 28 millimetres
Adding 43 and 28
43 + 28 = 40 + 20 + 3 + 8 = 60 + 11 = 71
Thus, the length of this line is 71 millimetres.
Write in centimetres as a decimal:
71 millimetres = 7 centimetres 1 millimetre = 7.1 centimetres
Convert the numbers to fractions
4.3 = \(\frac {43}{10}\)
2.8 = \(\frac {28}{10}\)
Add the fractions:
\(\frac{43}{10}+\frac{28}{10}=\frac{43+28}{10}=\frac{71}{10}\)
Convert the fraction back to the decimal form.
\(\frac {71}{10}\) = 7.1
The length of the line is 7.1 centimetres.

Question 8.
A jar contains 3.5 litres of oil, and 6.25 litres more is poured into it. How much oil does the jar contain now?
Answer:
Convert just the numbers to fractions:
3.5 = \(\frac {35}{10}\)
6.25 = \(\frac {625}{100}\)
We can write \(\frac {35}{10}\) also as a fraction with denominator 100:
\(\frac{35}{10}=\frac{35 \times 10}{10 \times 10}\) = \(\frac {350}{100}\)
Now we can add like this:
\(\frac{35}{10}+\frac{625}{100}=\frac{350}{100}+\frac{625}{100}=\frac{300+600+50+25}{100}\)
= \(\frac{350+625}{100}\)
= \(\frac {975}{100}\)
Amount of oil the jar contains = 9.75 litres

Question 9.
A person bought 2.5 kilograms of rice and 3.125 kilograms of vegetables. What is the total weight?
Answer:
Converting into fractions
2.5 = \(\frac {25}{10}\)
3.125 = \(\frac {3125}{1000}\)
To add these, we change \(\frac {25}{10}\) to a form with a denominator of 1000.
\(\frac{25}{10}=\frac{25 \times 100}{10 \times 100}\) = \(\frac {2500}{1000}\)
Now, we add the fractions:
\(\frac{25}{10}+\frac{3125}{1000}=\frac{2500}{1000}+\frac{3125}{1000}\) = \(\frac{2500+3125}{1000}\)
One way of adding 2500 and 3125 is this:
2500 + 3125 = 2000 + 3000 + 500 + 125 = 5000 + 625 = 5625
So, we can continue our addition of fractions:
\(\frac{25}{10}+\frac{3125}{1000}=\frac{2500+3125}{1000}\) = \(\frac {5625}{1000}\)
Converting this to decimals:
\(\frac {5625}{1000}\) = 5.625
Thus, the total weight is 5.625 kilograms.

Subtraction of Decimal Numbers
Example: From an 8.5 centimetres long eerkkil, a 3.2 centimetres long piece is broken off. What is the length of the remaining piece?
Thinking in terms of numbers alone, what we need is to subtract 3.2 from 8.5.
We change the numbers to fractions.
8.5 = \(\frac {85}{10}\)
3.2 = \(\frac {32}{10}\)
Now we can subtract:
\(\frac{85}{10}-\frac{32}{10}=\frac{85-32}{10}\)
One way to subtract 32 from 85 is this:
85 – 32 = (80 – 30) + (5 – 2) = 50 + 3 = 53
So we get \(\frac{85}{10}-\frac{32}{10}=\frac{53}{10}\)
Finally, we switch back to decimals:
\(\frac {53}{10}\) = 5.3
Thus, the length of the remaining piece of eerkkil is 5.3 centimetres.

Question 10.
From an 8.5 centimetres long eerkkil, a 3.7 centimetres long piece is broken off. What is the length of the remaining piece?
Answer:
We start as before by converting the decimals to fractions:
8.5 = \(\frac {85}{10}\)
3.7 = \(\frac {37}{10}\)
And then subtract
\(\frac{85}{10}-\frac{37}{10}=\frac{85-37}{10}\)
We have seen in earlier classes that subtraction like 85 different ways.
For example,
85 – 37 = (85 – 35) – 2 = 50 – 2 = 48
85 – 37 = (87 – 37) – 2 = 50 – 2 = 48
85 – 37 = (85 – 40) + 3 = 45 + 3 = 48
Anyway, we find
\(\frac{85}{10}-\frac{37}{10}=\frac{48}{10}\)
Changing back to decimals,
\(\frac {48}{10}\) = 4.8
The remaining piece of eerkkil is 4.8 centimetres long.

Question 11.
There are 15 kilograms of rice in a sack. 4.25 kilograms from this are put in a bag. How much rice remains in the sack?
Answer:
Thinking just in terms of numbers, what we have to do is subtract 4.25 from 15.
Write 4.25 as a fraction:
4.25 = \(\frac {425}{100}\)
Write 15 as a fraction with a denominator of 100.
15 = \(\frac{15}{1}=\frac{15 \times 100}{1 \times 100}=\frac{1500}{100}\)
Subtracting \(\frac{1500}{100}-\frac{425}{100}=\frac{1500-425}{100}\)
We can do 1500 – 425 in several ways:
1500 – 425 = 1000 + 500 – 425 = 1000 + 75 = 1075
1500 – 425 – 1425 – 425 + 75 = 1000 + 75 = 1075
1500 – 425 = 1500 – 500 + 75 = 1000 + 75 = 1075
Thus, we have:
\(\frac{1500}{100}-\frac{425}{100}=\frac{1075}{100}\)
Changing back to decimals:
\(\frac {1075}{100}\) = 10.75
So, there are 10.75 kilograms of rice still in the sack.

Reviewing SCERT Class 8 Basic Science Solutions and Kerala Syllabus Class 8 Basic Science Chapter 1 Measurement and Units Question Answer Notes Pdf can uncover gaps in understanding.

Class 8 Basic Science Chapter 1 Measurement and Units Question Answer Notes

Class 8 Basic Science Chapter 1 Notes Kerala Syllabus Measurement and Units Question Answer

Measurement and Units Class 8 Questions and Answers Notes

Let’s Assess

Question 1.
Identify the odd one out in each group and explain common features of the others.
I a) Kilogram b) Kilometre c) Second d) Mole
II a) Time b) Area c) Mass d) Electric current
III a) Metre b) Kilogram c) Second d) Degree Celsius
Answer:
I. b) Kilometre
Kilometre is a unit of length. Others are SI unit of mass, time and amount of substance respectively.

II. b)Area
Area is a derived quantity. Others are fundamental quantities.

III. d) Degree Celsius
This is a unit of temperature. Others are SI unit of length, mass and time respectively.

Question 2.
Different units of length are given below. Fill in the table below.

Answer:

Unit	Relationship with metre
Kilometre	1 km = 1000 metre
Millimetre	1 m = 1000 millimetre
Centimetre	100 cm = 1m

Question 3.
Convert the following measurements to SI units without changing their values.
a) 2000 g
b) 1 h
c) 1.5 km
d) 200 cm
Answer:
a) 2000 g = \(\frac{2000}{1000}\) = 2 kg
b) 1 h = 60 × 60 = 3600 s
c) 1.5 km= 1.5 × 1000 = 1500 m
d) 200cm = \(\frac{200}{100}\) = 2m

Question 4.
Different units of mass are given below. Arrange them in the ascending order of their values.
a) Kilogram
b) Milligram
c) Quinta
d) Gram
Answer:
b) Milligram < d) Gram < a) Kilogram < c) Quintal

Basic Science Class 8 Chapter 1 Question Answer Kerala Syllabus

In our daily life, it is necessary to measure and state the characteristic properties of objects and phenomena. Such measurable quantities are physical quantities.
Question 1.
Observe the following situations in our life. Find the physical quantities in each of them.


Record the quantities you identified, in the table.
Answer:

Situation	Physical quantity
1. Measuring the depth of a pit	Length
2. Measuring the weight of vegetables	Mass
3. Taking measurements by a tailor	Length
4. Using a stopwatch in a race	Time
5. Measuring blood pressure	Pressure
6. Measuring body heat	Temperature

Question 2.
Find and write more physical quantities that you are familiar with.
Answer:

• Electric current
• Amount of substance
• Luminous intensity

All the physical quantities cannot be measured directly. In situations where direct measurement is not possible, we can write them with reference to other physical quantities.

Question 3.
Find out the physical quantities mentioned in the table 1.1 and list them below.
Answer:

1. Length
2. Mass
3. Time
4. Temperature

Question 4.
Look at the pictures. What are the physical quantities in these situations?

Answer:
• Area
• Volume

Question 5.
Record how each of them is found out and complete the table appropriately.

Answer:

Situation	Physical Quantity	Method of Finding
For painting the wall	Area	Area = Length × Width
Measurement of medicine/liquid	Volume	Volume = Area of the measuring jar × Height

a) Which are the quantities used here to find area and volume?
Answer:
Length, width, area and height.

b) All of them are distances between two positions, aren’t they?
Answer:
Yes. All of them are distances between two positions.

The distance between two positions represents a physical quantity called length. We have used the fundamental quantity of length to find the quantities of area and volume. Such quantities that can be found out using fundamental quantities are called derived quantities.

Quantities that can be expressed in terms of fundamental quantities are derived quantities.

See, how the mass is marked on a gas cylinder.

Mass marked on the cylinder = 14.2 kilogram
Here, the physical quantity of mass is indicated using a numerical value i.e., 14.2 (magnitude) and a unit i.e., kilogram.

Question 6.
Similarly, complete the table with the physical quantities shown in the pictures below, along with their numerical values and units.

Answer:

Situation	Physical quantity	Numerical Value	Unit	Mode of marking measurements
Fig. 1.12	Temperature	37.8	Celsius	37.8° C
Fig. 1.13	Height	165	Centimetre	165 cm
Fig. 1.14	Mass	1	Kilogram	1kg

A physical quantity is expressed by a number indicating its value followed by its unit.

Question 7.
Tabulate the measurements from both the activities.

Answer:

Activity	Physical quantity	Reference object used for measurement	Recorded quantity
Measuring the height of the child	Length	Longer stick	2 stick
		Shorter stick	6 stick
Measuring the quantity of water	Volume	Larger glass	5 glass
		Smaller glass	10 glass

Question 8.
Analyze the table. Two different reference objects were used in each case to determine a physical quantity.
a) In both cases, are the measurements obtained the same?
Answer:
No, the measurements obtained are not the same.

b) Why are the measurements not equal?
Answer:
It is because the reference object used for each measurement is different.

c) When everyone uses the same reference object, isn’t measurement the same?
Answer:
When the same reference object is used, the measurement is the same.
When a physical quantity is measured anywhere in the world, the measurement should be the same. For this, everyone should adopt a fixed reference. This is called the unit of a physical quantity.

A unit is a standardised reference accepted universally to measure a physical quantity.

In the past, different units were used for measurement and recording in each region. For example, units like the foot, cubit and hand span were used locally to measure length.

Question 9.
Different units were also used in other countries. What would be the practical problems of using different units in different countries?
Answer:

• Low accuracy
• Difficulty for the people in other regions to analyse measurements.
• Lack of uniformity
• Difficulty with transaction

Today, the unit ’metre’ is used everywhere in the world to measure length.

There are internationally accepted units for all physical quantities. This is called the International System of Units, abbreviated as ‘SI’ units. Measurement using the SI units always has a universal result.

Now we can understand that with the help of SI units which always, has a universal result, parts of vehicles and equipment we use, even if manufactured in different countries can be perfectly assembled in any factory in the world.

Different units are required for the same physical quantity in various contexts. Larger units are used for larger quantities and smaller units for smaller quantities.

Question 10.
Now complete the following relationship given below.
Answer:
1 metre = 100 centimetre
1 centimetre = 10 millimetre
1 metre = 1000 millimetre
There are situations where we have to use smaller measurements.

Question 11.
Pay attention to the notice of a municipality.

Prohibited The sale of plastic bags below 30 micron is prohibited in shops within the limit of the municipality with effect from 30.10.2022.

What is the measurement mentioned in the notice?
Answer:
The measurement mentioned is micron. Micron is the abbreviation of micrometre.

Question 12.
How many micrometres would make one metre?
Answer:
1 metre = 1000000 micrometre

There are also situations where we need units larger than metre.
The abbreviation “km” on the traffic sign stands for kilometre.
1 kilometre = 1000 metre
Are there situations where we need even larger units? Read the following excerpt from a science article.

Scale of the Solar System Astronomical Unit (AU) is the average distance from the Earth to the Sun. It is approximately 150 million kilometre. A light year is the distance light travels in a year in vacuum. Light travels at a speed of approximately 300,000 km/s.

Question 13.
Discuss the situations where the units mentioned in the article are used.
Answer:
Astronomical unit is used to measure the distance between Earth and the Sun, distance from Sun to different planets and distance between planets in our solar system. Light year is used to measure the distance between Earth and stars, distance between galaxies or stars.

Question 14.
Look at the picture of weighing apples in a shop. The weight is measured by placing weight blocks on one side of the scale.

Here, why are weight blocks placed on one side?
Answer:
This is done to ensure that the apples taken have the same mass as weight of blocks.

The amount of matter contained in a substance is its mass.

Question 15.
Examine the picture of the weight blocks shown in figure below. What is written on them?

Answer:
The mass of the weight block is written on them

The unit of mass is the kilogram. Its symbol is ‘kg’.

We need units other than kilogram for mass.

Question 16.
You might have noticed the quantity of toothpaste and tablet printed on their packages. What does it mean?

Answer:
The quantity printed on them indicates their mass.

Milligram and gram are the smaller units of mass. 1 gram = 1000 milligrams

Question 17.
You might have seen trucks carrying load. Which are the larger units commonly used in such situations?
Answer:
Quintal and tonne are the larger units of mass commonly used in such situations.
Identify the relationship between the units of mass and kilogram from the table given below.

Unit	Relation to kilograms
Milligram	1 kilogram = 1000000 milligram
Gram	1 kilogram = 1000 gram
Quintal	1 quintal = 100 kilogram
Tonne	1 tonne = 1000 kilogram

Question 18.
Minute and hour are the other units used to denote time. Identify the relationship between these units and ‘second’.

Answer:

Unit	Relationship with second
Minute	1 minute = 60 second
Hour	1 hour = 3600 second

Question 19.
The figure shows thousand cubes each with sides of 1 cm arranged to form a large cube.

If volume of the large cube is 1 litre. Can you complete writing the relationship between various units based on the figure?
Answer:
1 litre = 1000 cm³
1 litre = 1000 millilitre

Question 20.
Take a cardboard box and calculate its volume. Fill it with sawdust and measure its mass. Then replace it with sand and find its mass. Tabulate the findings.

Answer:

Substance	Mass	Volume	\(\frac{\text { Mass }}{\text { Volume }}\)
Sawdust	30 g	200 cm3	\(\frac{30}{200}\) = 0.15 g/cm3
Sand	320 g	200 cm3	\(\frac{320}{200}\) =1.6 g/cm3

The mass of a substance per unit volume is called its density. Density = \(\frac{\text { Mass }}{\text { Volume }}\)

In the table given, even though the volume of sawdust and sand is the same, see how the mass per unit volume is calculated.

If volume is the same, objects with higher mass will have higher density. In the case of a particular substance, density is a fixed number.

Question 21.
Why is density displayed on the fuel dispenser in a petrol pump?
Answer:
Displaying density on the fuel dispenser in petrol pumps helps to check if the fuel is pure and not mixed with anything. If the fuel is adulterated with some impurities, then the density will change. To ensure that it is not adulterated, the density is displayed.

Question 22.
What are the characteristics of SI units?
Answer:

• They are standardised units.
• They are internationally accepted.
• Units of all other quantities can be expressed in terms of these units.

Question 23.
The table below shows common errors that may occur when writing units. Compare each of these with the correct version and suggest a general rule for each.

Answer:

Unit written incorrectly	General rules
1000 KG/M3 1.5 KG	Use lower case of the English alphabet.
1000 kgs/m3 1.5 kgs	Do not use the plural form for symbols.
1000kg/ m3 1.5kg	While writing units along with a numerical value, there must be a single space between them.
1000 kg/m/m/m	Do not use more than one slash in one derived unit.
1000 kg/ cubic metre 1000 kilogram per m3	Do not mix a symbol of a unit with the name of a unit.
1 kg 500 g	Do not use more than one unit to express a physical quantity.
273 Kelvin	Use only lowercase letters when writing the name of a unit instead of its symbol.

Now let us get familiar with some other rules.

Physical quantity	Correct method	Incorrect method	Rule
Force	N	n	The symbols of the units formed from the names of individuals should be written using uppercase of the English alphabet.
Length	60 cm is the length of the desk.	60 cm. is the length of the desk.	No full stop or comma should be used after the symbol. They can be used at the end of the sentence.
	The length of the desk is 60 cm.	The length of the desk is 60 cm
Energy	N.m Nm	Nm	A full stop/space should be used between the units formed as multiples of units.

Question 24.
What are the rules to be followed internationally when writing units and their symbols?
Answer:

1. Use lower case of the English alphabet to write the symbol of the units.
   e.g. 1000 KG/M³– wrong, 1000 kg/m³ – correct
2. Use only lowercase letters when writing the name of a unit.
   e.g. 273 Kelvin-wrong, 273 kelvin- correct
3. The symbols of the units formed from the names of individuals should be written using uppercase of the English alphabet.
   e.g. The unit of the physical quantity force is newton. This is named after sir Isaac Newton. The symbol is denoted as N.
4. While writing units along with a numerical value, there must be a single space between them, e.g. 1.5kg- wrong, 1.5 kg -correct
5. Do not use the plural form for symbols.
   e.g. 1.5 kgs- wrong, 1.5 kg -correct
6. Do not use more than one slash in one derived unit.
   e.g. 1000 kg/m/m/m -wrong, 1000 kg/m³– correct
7. Do not mix a symbol of a unit with the name of a unit.
   e.g. 1000 kg/ cubic metre-wrong, 1000 kg/m³– correct, 1000 kilogram per cubic metre (correct)
8. Do not use more than one unit to express a physical quantity.
   e.g. 1kg 500 g (wrong) 1.5 kg ( correct)
9. No full stop or comma should be used after the symbol. They can be used at the end of the sentence, e.g. 75 cm is the length of a table, (correct) 75 cm. is the length of a table, (wrong)
10. A full stop/space should be used between the units formed as multiples of units, e.g. Nm – wrong, N.m or N m – correct

Question 25.
What are the instruments used to measure length?
Answer:
Scale, tape.

Question 26.
Look at the picture given.

a) Measure the length of a pen using a scale and write it down.
b) Also, use a measuring tape to determine your height.
c) What is the unit on the scale/tape used?
d) What is the smallest measurement possible using the scale/measuring tape?
Answer:
a) Length of the pen = 14.7 cm
b) Your height = 138 cm
c) Centimetre
d) 0.1 cm

The smallest value that can be measured using an instrument is called its least count.

Question 27.
The least count of a commonly used scale is 0.1 cm . Are there instruments with a least count smaller than this? Find out and write.
Answer:
Vernier caliper is an instrument used to measure the length of rod, diameter of a cylinder or sphere shaped object etc. Least count: 0.01 cm (or 0.1 mm)
Screw gauge is an instrument used to measure the thickness of glass plates and diameter of thin wires. Least count – 0.001 cm (or 0.01 mm).

Question 28.
The figure shows some papers stacked together.

Measure the thickness of the paper stack and write it down.
Answer:
Number of papers in the paper stack = 50
Thickness of the paper stack = 5 cm
Thickness of one paper = \(\frac{\text { Thickness of the paper stack }}{\text { Number of papers }}\) = \(\frac{5}{500}\)
= 0.01 cm = 0.01 mm

Question 29.
What unit is used in the measuring jar?
Answer:
millilitre

Question 30.
What is the least count of the measuring jar?
Answer:
l ml
Initial water level before dipping the stone = 50 ml
Water level after dipping the stone = 78 ml
Volume of the stone = 78 – 50 = 28 ml

Class 8 Basic Science Chapter 1 Question Answer Extended Activities

Question 1.
Identify the different units used in our locality for measuring length and mass in the past.
Answer:
Some of the different units used in our locality for measuring length and mass in the past are tabulated.

Unit of length	Unit of mass
Vaara Muzham Feet Kol Furlong Mile	Chan Kizhi Edangazhi Nazhi Para Padi

Question 2.
Prepare a seminar paper on the rules to be followed when writing ‘units’.
Answer:
Title: Rules to be followed when writing units.

Introduction: In our day to day life and in science, we make use of different units to measure various physical quantities like length, mass, time etc. A physical quantity is expressed by a number indicating its value followed by its unit. It is very important to express units in the right way to avoid confusion and to maintain accuracy in measurements.

Rules to be followed when writing units
1. The symbols of units are normally written using small letters in the English alphabet.
e.g. m (metre), s (second)

2. The symbol of units named after persons should be expressed by capital letters of the English alphabet.
e.g. The unit of the physical quantity electric current is ampere. This is named after Andre-Marie Ampere. The symbol is A.

3. While writing the names of units never use capital letters.
e.g. kelvin (correct) Kelvin (wrong)

4. Never use the plural form for symbols.
e.g. 10 kg (correct) 10 kgs (wrong)

5. Never use full stop or comma after a symbol except at the end of a sentence.
e.g. 75 cm is the length of a table. (correct)
75 cm. is the length of a table, (wrong)

6. While writing derived units a slash (/) is used to denote division. But never use more than one slash in one derived unit.
e.g. m/s² (correct) m/s/s (wrong)

7. When a derived unit is expressed as the product of other units use a dot or a space between them, e.g. N.m or N m

8. Do not mix the name of a unit with the symbol.
e.g.kg/m³ (correct)
kilogram per cubic metre (correct)
kg/cubic metre (wrong)
kilogram per m³ (wrong)
kg per m³ (wrong)
kilogram/m³ (wrong)

9. While writing units along with a numerical value, there must be single space between them, e.g. 273 K (correct), 273K (wrong)

10. Never use more than one unit to express a physical quantity, e.g. 10.25 m (correct) 10 m 25 cm (wrong)

Conclusion
Following these rules will help us to write the units in its clear and correct manner so that it can be understood by all.

Measurement and Units Class 8 Notes

Class 8 Basic Science Measurement and Units Notes Kerala Syllabus

• Fundamental quantities are quantities that exist independently and cannot be expressed in terms of other quantities.
• Quantities that can be expressed in terms of fundamental quantities are derived quantities.
• A physical quantity is expressed by a number indicating its value followed by its unit.
• A unit is a standardised reference accepted universally to measure a physical quantity.
• There are internationally accepted units for all physical quantities. This is called the International System of Units, abbreviated as ‘SI’ units. Measurement using the SI units always has a universal result.
• The SI unit of length is metre. Its symbol is ‘m’. Centimetre, millimetre, kilometre, etc. are the other units of length.
• The amount of matter contained in a substance is its mass. The unit of mass is the kilogram. Its symbol is ‘kg’. Milligram and gram are the smaller units of mass.
• Quintal and tonne are the larger units of mass commonly used.
• The SI unit of time is the second. Its symbol is ‘s’.
• Minute and hour are the other units used to denote time.
• The volume of an object is the amount of space it occupies. The SI unit of volume is cubic metre.
  It’s symbol is m³.
• The mass of a substance per unit volume is called its density. Density = \(\frac{\text { Mass }}{\text { Volume }}\)
• Fundamental units are the units of fundamental quantities.
• Characteristics of SI units
  • They are standardised units.
  • They are internationally accepted.
  • Units of all other quantities can be expressed in terms of these units.
• Derived units are units that can be stated using fundamental units or that depend on fundamental units.
• The smallest value that can be measured using an instrument is called its least count.

INTRODUCTION

In our daily life, we often need to measure physical quantities like length, mass and time. In some situations, it is very important to be accurate in these measurements. Long ago, people had many problems because they did not have accurate ways to measure, and different places used different types of measuring scales. This caused confusion and mistakes. This chapter deals with fundamental quantities and derived quantities, units of physical quantities, fundamental and derived units, rules for writing the units and measuring instruments.

FUNDAMENTAL QUANTITIES AND DERIVED QUANTITIES

There are many physical quantities. Among them length, mass, time, electric current, temperature, amount of substance and luminous intensity are called fundamental quantities. All other quantities can be expressed in terms of these fundamental quantities.

Fundamental quantities are quantities that exist independently and cannot be expressed in terms of other quantities.

UNITS OF PHYSICAL QUANTITIES
Activity

• Mark the height of a child in your class on the wall using a pencil as shown in the figure 1.5. Each one in the class may measure the height using two sticks of different lengths.
• Fill a bucket with water. Measure the water in it with two glasses of different sizes (Figure 1.16).

DIFFERENT UNITS OF LENGTH

The SI unit of length is metre. Its symbol is ‘m’. Centimetre, millimetre, kilometre, etc. are the other units of length.

The picture shows part of a metre scale.

Take a metre scale from the science lab and examine it. You can see small and large lines on the metre scale. The distance between two consecutive large lines is one centimetre and the distance between small lines is one millimetre.

DIFFERENT UNITS OF TIME

The SI unit of time is the second. Its symbol is ‘s’.

VOLUME

The volume of an object is the amount of space it occupies. The SI unit of volume is cubic metre. It’s symbol is m3.

FUNDAMENTAL AND DERIVED UNITS

FUNDAMENTAL UNITS
In 1960, an international conference held in Paris approved the International System of Units or SI units as the universal system of units for measurements. Under this system, units were assigned to all the fundamental quantities.

Fundamental units are the units of fundamental quantities.

Note the fundamental units and their symbols given below.

DERIVED UNITS
We have learned about derived quantities. Such as volume and density, whose units are obtained from fundamental units.

We can write the derived units by relating fundamental units one another. Derived units are formed using fundamental units.

See how derived units are formulated in the table given.

Derived quantities	Equation	Unit
Area	Area = length × breadth	m × m = m2
Volume	Volume = length × breadth × height	m × m × m = m3
Density	Density = \(\frac{\text { Mass }}{\text { Volume }}\)	kg/m3

Derived units are units that can be stated using fundamental units or that depend on fundamental units.

RULES FOR WRITING THE UNITS
Observe the correct notation of units for two physical quantities.

Quantity	Unit
Mass of 1.5 litre of water	1.5 kg
Density of water	1000 kg/m3 1000 kilogram per cubic metre

MEASURING THE VOLUME USING A MEASURING JAR
Let’s try to find the volume of a stone. Pour some water into a measuring jar and mark its level. Tie the stone with a thread and dip into the water. Observe the rise in the water level. From this, we can calculate the volume of the stone which is equal to the volume of water displaced.

MEASURING TIME USING A STOPWATCH
A stopwatch is used to measure a time intervals. As shown in the figure, tie a metal ball using a thread and hang it. Pull the ball slightly and release it to oscillate. Observe the motion. Measure the time taken for 10 oscillations using a stopwatch. Record the measurement.

Time required for 10 oscillations = 10 s
A good understanding of physical quantities will help you in further studies and on the proper use of measurement and units in daily life.

Students can use Class 8 Malayalam Adisthana Padavali Notes Pdf and കുരുവിയും കാട്ടുതീയും Kuruviyum Kaattu Theeyum Summary in Malayalam to grasp the key points of a lengthy text.

Class 8 Malayalam Kuruviyum Kaattu Theeyum Summary

Kuruviyum Kaattu Theeyum Summary in Malayalam

കുരുവിയും കാട്ടുതീയും Summary in Malayalam

എഴുത്തുകാരനെ പരിചയപ്പെടാം

ആനന്ദിന്റെ കഥകൾ – സച്ചിദാനന്ദ്
തൂലികാനാമം – ആനന്ദ്

പ്രശസ്തനായ ഒരു മലയാള നോവലിസ്റ്റും എഴുത്തുകാരനുമാണ് ആനന്ദ് എന്നറിയപ്പെടുന്ന പി. സച്ചിദാനന്ദൻ. 1936 ൽ ഇരിങ്ങാലക്കുടയിലാണ് ജനിച്ചത്. തിരുവനന്തപുരം എൻജിനീയറിങ്ങ് കോളേജിൽ നിന്ന് സിവിൽ എൻജിനീ യറിങ്ങിൽ ബിരുദം. നാലുകൊല്ലത്തോളം പട്ടാളത്തിൽ സേവനമനുഷ്ഠി ച്ചിട്ടുണ്ട്. ന്യൂഡെൽഹിയിൽ സെൻട്രൽ വാട്ടർ കമ്മീഷനിൽ പ്ലാനിങ്ങ് ഡയറ ക്ടറായി വിരമിച്ചു. ശില്പ കലയിലും തത്പരനായ ആനന്ദിന്റെ പല നോവലു കളിലും മുഖച്ചിത്രമായി അദ്ദേഹം നിർമിച്ച ശില്പങ്ങളുടെ ഫോട്ടോയാണ് ഉപയോഗിച്ചിട്ടുള്ളത്. 2016 ലെ കൊച്ചിൻ മുസിരിസ് ബിനലയിൽ അദ്ദേഹം ശിൽപ്പങ്ങൾ പ്രദർശിപ്പിച്ചിരുന്നു.

വീടും തടവും, ജൈവമനുഷ്യൻ ഇവ കേരള സാഹിത്യ അക്കാദമി അവാർഡും മരുഭൂമികൾ ഉണ്ടാകുന്നത് വയലാർ അവാർഡും ഗോവർദ്ധനന്റെ യാത്രകൾ 1997ലെ കേന്ദ്ര സാഹിത്യ അക്കാദമി അവാർഡും നേടി. മഹാശ്വേതാദേവിയുടെ ‘കവി ബന്ദ്യഘടിഗായിയുടെ ജീവിതവും മരണവും’ എന്ന കൃതിയുടെ മലയാള വിവർത്തനത്തിന് 2012ൽ കേന്ദ്രസാഹിത്യ അക്കാദമി പുരസ്കാരം ലഭിച്ചു. 2019 ലെ എഴുത്തച്ചൻ പുരസ്കാരം ലഭിച്ചു.

വ്യവസ്ഥകളിലും ശീലങ്ങളിലും ക്രമപ്പെട്ടുപോയ മനുഷ്യരുടെ അകമേനിന്നു പുറപ്പെടുന്ന ഒച്ചയാണ് ആനന്ദിന്റെ കഥകൾ. കരച്ചിലോ, വിലാപങ്ങളോ അല്ല; സമൂഹത്തിന്റെയും ചരിത്രത്തിന്റെയും രാഷ്ട്രീയ ത്തിന്റെയും ജീർണ്ണസത്തകളിലേക്കുള്ള ശ്രദ്ധ ക്ഷണിക്കലാണ് ആ ശബ്ദം. ആ ഒച്ചകൾ നമുക്കു ചുറ്റും പ്രതിധ്വനിക്കുന്നു. സമകാലീനതയുടെ ആത്മകഥകളെന്നു വിശേഷിപ്പിക്കാ വുന്നവയാണ് ആനന്ദിന്റെ ശ്രദ്ധേയങ്ങളായ രചനകൾ.

പാഠസംഗ്രഹം

‘കുരുവിയും കാട്ടുതീയും’ ഏറെ സമകാലീന പ്രസക്തിയുള്ള ആഴമുള്ള സാമൂഹിക ചിന്ത കാഴ്ചവയ്ക്കുന്ന കഥയാണ് പ്രകൃതിയിലെ ദുരന്തമായി കാട്ടുതീ പടർന്നപ്പോൾ മൃഗങ്ങളും പക്ഷികളും ജീവനുവേണ്ടി ഓടി രക്ഷപ്പെടുന്നു. എന്നാൽ ഒരു കൊച്ചുകുരുവി മാത്രം, സ്വല്പമെങ്കിലും പ്രതിരോധിക്കാൻ ശ്രമിക്കുന്നു. തന്റെ ചെറുചുണ്ടിൽ വെള്ളം എടുത്ത് തീയിൽ തളിച്ച് തീ കെടുത്താൻ കുരുവി കഠിന ശ്രമം തുടരുന്നു. വലിയ കാട്ടുതീ അണയ്ക്കാൻ ചെറിയ ചുണ്ടിൽ വെള്ളം തേവുന്ന കുരുവിയെ കണ്ടു മഴദേവൻ പരിഹസിക്കുമ്പോൾ, കുരുവി മറുപടി പറയുന്നു: ‘ഞാൻ എനിക്കാവുന്നത് ചെയ്യുന്നു.’ മഴമേഘത്തിന് ‘തീയണയ്ക്കാൻ’ കഴിവുണ്ടായിട്ടും പ്രവർത്തിക്കാത്തിനെ വ്യംഗ്യമായി വിമർശിക്കുന്നു കുരുവി.

ഈ വാചകം കഥയുടെ ആത്മാവാണ്. മനുഷ്യൻ ശക്തരായും ശേഷിയുള്ളവരായും ഇരിക്കെ ഭൂമിയിലെ നശീകരണങ്ങളോടും ദുരന്തങ്ങളോടും ഉള്ള അവന്റെ മനോഭാവത്തെ ചോദ്യം ചെയ്യുകയാണ് ഈ കുരുവിയുടെ വാക്കുകളിലൂടെ കഥാകാരൻ. ഇവിടെ സാമാന്യേന ശേഷി കുറഞ്ഞ കൊച്ചുകുരുവി പോലുള്ള ജീവിയും സ്വന്തം കഴിവിനൊത്ത് വല്ലതും ചെയ്യുകയാണ്. അതിനുവേണ്ടിയാണ് കുരുവി ശ്രമിക്കുന്നത് പല നിർണായക സന്ദർഭങ്ങളിലും മനുഷ്യർ നമ്മൾ ഒരാൾ വിചാരിച്ചാൽ ഒന്നും സാധിക്കുകയില്ലെന്ന് പറഞ്ഞു മൗനദർശിയായി നിൽക്കാറുണ്ട്. ചെറുശേഷിയുള്ളതായിരുന്നാലും തന്റെ പ്രവർത്തി മറ്റുള്ളവരിൽ ഉത്തരവാദിത്ത ബോധം വളർത്തുമെന്നും മൃഗങ്ങൾ തന്നെപ്പോലെ ചിന്തിച്ചാൽ കാട്ടുതീ അണയ്ക്കാം എന്നുമുള്ള ബോധ്യമാകുരുവിക്ക് ഉണ്ടായിരിക്കണം. (നമ്മുടെ സ്വാതന്ത്ര്യ സമര ചരിത്രത്തിലെ ദണ്ഡിയാത്ര ഓർമ്മിക്കുക.) ഒരാളുടെ ചെറിയ പ്രവർത്തനം പോലും വലിയ പ്രചാരണങ്ങൾക്ക് വഴിവെക്കാം എന്നതിന്റെ മാതൃക ചിത്രമാണ് ഈ കുരുവി. അനാസ്ഥയുടെയും ഉപേക്ഷയുടെയും ആധുനിക സമൂഹ മനോഭാവത്തിന് എതിരായ പ്രതിരോധം തന്നെയാണിത്.

ഇന്നത്തെ കാലത്ത് പരിസ്ഥിതി പ്രശ്നങ്ങൾ, സാമൂഹിക അനീതികൾ, യുദ്ധങ്ങൾ, സാംസ്കാരിക മൂല്യച്ചുതി തുടങ്ങിയ പ്രശ്നങ്ങൾ മനുഷ്യന്റെ മുന്നിലുണ്ട്. അവയെ തടയാൻ പുതിയ തലമുറ മൗനപരമായ മനോഭാവം സ്വീകരിക്കുമ്പോൾ, അങ്ങേയറ്റത്തെ അനാസ്ഥയും നിരുത്തരവാദപരവും, പുരോഗമന കാഴ്ചപ്പാടുകളുടെ മറവിൽ നടത്തുന്ന ചൂഷണവും ഭൂമിയെ ആകെ ഒരു കാട്ടുതീ പോലെ പടർന്നുപിടിക്കുന്നത് കഥാകാരൻ ഈ കഥയിൽ ചേർത്ത് വച്ചിരിക്കുന്ന സത്യമാണ്.

‘കുരുവിയും കാട്ടുതീയും’ എന്ന കഥയിലൂടെ ആനന്ദ് സമകാലീന സമൂഹത്തിന് മുന്നിൽ ആധുനിക ചോദ്യങ്ങൾ ഉന്നയിക്കുന്നു: ‘നിനക്ക് എന്ത് ചെയ്യാനാകും,’, ‘നിനക്ക് അതിന് മനസ്സുണ്ടോ?’ അതിനുള്ള ഉത്തരം കഥാകൃത്ത് നല്കുന്നില്ല; മറിച്ച്, അത് വായനക്കാരനോട് തന്നെ ആവശ്യപ്പെടുകയാണ്. ചെറുതെങ്കിലും ഒരു കുരുവിയുടെ നീക്കം, വലിയൊരു മാറ്റത്തിന് തുടക്കമാകാമെന്നത് ഈ കഥയുടെ ഉദാത്തമായ സന്ദേശമാണ്.

പുതിയ പദങ്ങൾ

പ്രാണവായു = പ്രാണൻ നിലനിർത്തുന്ന വായു (ഓക്സിജൻ)
ജീവജലം = ജീവദായകമായ ജലം
അന്നം = ആഹാരം, ഭക്ഷ്യവസ്തു
മടയത്തം = വിഡ്ഢിത്തം / വിഫലമായ ശ്രമം
ആളിക്കത്തുന്ന = വളരെ വേഗത്തിൽ കത്തുന്ന വേഗത്തിൽ വ്യാപിക്കുന്ന

Practicing with Std 8 Malayalam Adisthana Padavali Notes Unit 1 Chapter 1 കുരുവിയും കാട്ടുതീയും Kuruviyum Kaattu Theeyum Notes Questions and Answers Pdf improves language skills.

കുരുവിയും കാട്ടുതീയും Question Answer Notes Std 8 Malayalam Adisthana Padavali Chapter 1

Class 8 Malayalam Adisthana Padavali Unit 1 Chapter 1 Notes Question Answer Kuruviyum Kaattu Theeyum

Class 8 Malayalam Kuruviyum Kaattu Theeyum Notes Questions and Answers

പാഠപുസ്തകത്തിലെ ചോദ്യങ്ങളും ഉത്തരങ്ങളും

കഥപറയാം

Question 1.
കഥ മൗനമായി വായിക്കൂ. സംഘമായി തിരിഞ്ഞ് ഒരാൾ ഒരുവാക്യം എന്ന ക്രമത്തിൽ ആശയം ചോർന്നുപോകാതെ പറയൂ.
Answer:
കൂട്ടുകാരെ മുകളിൽ പറഞ്ഞതുപോലെ ചെയ്യുമല്ലോ…

അഭിപ്രായ കുറിപ്പ്

Question 1.
കാട്ടുതീ ഒത്തിരി പക്ഷികളുടെയും മൃഗങ്ങളുടെയും ജീവനെടുക്കുന്നത് കാണുന്നില്ലേ? എന്ന് കുരുവി മഴ ദേവനോട് ചോദിക്കുന്നു എന്നാൽ മഴ ദേവൻ എന്താണ് ചെയ്തത് രണ്ടുപേരുടെയും മനോഭാവങ്ങളിൽ എന്ത് വ്യത്യാസമാണുള്ളത്? നിങ്ങൾ ആരുടെ ഭാഗത്ത് നിൽക്കുന്നു? നിങ്ങളുടെ അഭിപ്രായം എഴുതുക.
Answer:
കുരുവി തീ അണയ്ക്കാൻ ശ്രമിക്കുന്നപ്പോൾ മഴദേവൻ അവളെ പരിഹസിക്കുന്നു. ഇത് രണ്ടുവിധമുള്ള മനോഭാവങ്ങൾ പ്രതിപാദിക്കുന്നു:

മഴദേവൻ: പ്രതീക്ഷയില്ലാത്ത, സംഭവിച്ചുകൊണ്ടിരിക്കുന്ന സാഹചര്യങ്ങൾ അഥവാ സംഭവങ്ങൾ മാറ്റാൻ കഴിയില്ലെന്ന് കരുതുന്ന, മറ്റുള്ളവരുടെ ശ്രമത്തെ പരിഹസിക്കുന്ന, വിഫലം എന്ന് കരുതുന്ന, നോക്കിക്കൊണ്ടിരിക്കാൻ മാത്രം തയ്യാറുള്ള മനോഭാവത്തോട് കൂടിയവരെ പ്രതിനിധീകരിക്കുന്നു.

എന്നാൽ കുരുവി: ധൈര്യവും ഉത്തരവാദിത്വബോധവും നിറഞ്ഞവൾ ആണ്. വലിയത് ചെയ്തില്ലെങ്കിലും കഴിയുന്നതുമാത്രം ചെയ്യുന്നവൾ.സഹജീവികൾക്കായി കരുതുന്നവൾ. സ്വതന്ത്രമായി നീതിനിമിത്തം പ്രവർത്തിക്കുന്നവൾ. കുഞ്ഞിക്കിളിയുടെ പ്രവൃത്തി മാതൃകാപരമാണ്. അതുകൊണ്ടു തന്നെ ഞാൻ കുഞ്ഞിക്കിളിയുടെ ഭാഗത്തു നിൽക്കുന്നു. പ്രതീക്ഷയും കരുണയും ഉള്ള ഈ ചെറിയ പക്ഷിയുടെ മനോഭാവമാണ് യഥാർത്ഥത്തിൽ മനുഷ്യനാകാനുള്ള ആദ്യപടി. മാറ്റങ്ങൾ ചെറുതായിരുന്നാലും, അവ തുടങ്ങേണ്ടത് നമ്മിൽ കൂടെയാണ്. നോക്കിക്കൊണ്ടിരിക്കുന്നതിലല്ല, പ്രവർത്തനത്തിലായിരിക്കണം നമ്മുടെ പങ്ക്.

കഥയെഴുതൂ, പതിപ്പാക്കു

Question 1.
ഈ കഥയിലെ കുരുവിയും മഴ ദേവനും തമ്മിലുള്ള സംഭാഷണം ശ്രദ്ധിച് കുരുവിയും കാടും തമ്മിലുള്ള സംഭാഷണം ആയിരുന്നുവെങ്കിൽ കഥാഗതിയിൽ എന്തു മാറ്റമാണ് സംഭവിക്കുക സങ്കൽപ്പിച്ച് കഥയെഴുതി പതിപ്പാക്കും…
കുരുവിയും കാടും തമ്മിലുള്ള സംഭാഷനത്തിൽ സംഭവിക്കുന്ന മാറ്റം.
Answer:
സങ്കല്പ കഥ:
• കാട്ടുതീ വലിയ ശബ്ദത്തോടെ കാട്ടിലാകെ പടരുമ്പോൾ, കുരുവി തന്റെ കുഞ്ഞി ചുണ്ടുകളിൽ പുഴയിൽ നിന്ന് വെള്ളം കൊണ്ടുപോയി തീ കെടുത്താൻ ഒരു വിഫല ശ്രമം നടത്തുകയാണ് അതു കണ്ട് കാട് കുരുവിയോട് പറഞ്ഞു:

കാട്: കുരുവി തീ പടർന്നു പിടിക്കുന്നിടത്ത് നീ എന്താണ് ചെയ്യുന്നത്? നിന്റെ കുഞ്ഞി ചിറകുകൾക്ക് പൊള്ളലേൽക്കും മുമ്പ് ഇവിടെ നിന്നും ദൂരേക്ക് പറന്നു പോകൂ…

കുരുവി: ഞാൻ വസിക്കുന്ന കാട് ആണ് നീ. നിന്നെ ഈ അവസ്ഥയിൽ ഉപേക്ഷിച്ച് ഞാൻ എങ്ങനെ പോകും? (അതും പറഞ്ഞ് കുരുവി വീണ്ടും പുഴയിലേക്ക് ചെന്ന് വെള്ളവുമായി വന്നു)

കാട്: ‘നിന്റെ സ്നേഹം ഞാൻ അറിയുന്നു കുരുവി പക്ഷേ നിനക്ക് ഈ തീ അണയ്ക്കുവാൻ ആവുകയില്ല നീ നിന്റെ വലിപ്പവും കഴിവും മനസ്സിലാക്കണം. ഞാൻ നിന്റെ മാത്രമല്ല മറ്റു ജീവജാലങ്ങളുടെയും കാടാണ്. പക്ഷേ എല്ലാവരും സ്വന്തം ജീവന് വേണ്ടി പരക്കം പായുന്നത് നീ കാണുന്നില്ലേ…?
നിന്റെ കുഞ്ഞി ചുണ്ടിലെ രണ്ടിറ്റു വെള്ളം കൊണ്ട് ഈ തീ അണയുകയില്ല. സ്വന്തം ജീവനെങ്കിലും രക്ഷപ്പെടുത്തി കൊള്ളൂ ഇനിയും ഒരു കാട് ദൂരെയെങ്ങാനും കാണും.

കുരുവി: ‘നിന്റെ വേദന എനിക്ക് മനസ്സിലാകുന്നു. നിന്റെ സ്നേഹവും. തീ നിന്നെ തിന്നുമ്പോൾ ഞാനെന്തെങ്കിലും ചെയ്യേണ്ടതല്ലേ? എനിക്കാവുന്നതു ഞാൻ ചെയ്യുന്നു. നിന്റെ വിയോഗം നോക്കി എനിക്ക് മൗനമായി ഇരിക്കാൻ കഴിയില്ല. ഞാൻ പ്രത്യാശിക്കുകയാണ്. എന്റെ പ്രവർത്തി മറ്റുള്ളവരെ ചിന്തിപ്പിച്ചിരുന്നുവെങ്കിൽ അവരും എന്നോട് ചേർന്ന് നിന്നെ സംരക്ഷിക്കാൻ പ്രയത്നിച്ചിരുന്നു എങ്കിൽ… ഇവിടന്നങ്ങോട്ട് ഈ കാടിനെ സംരക്ഷിക്കാൻ, തീ പടരുന്നത് തടഞ്ഞു നിർത്തുവാൻ കഴിയുമായിരിക്കാം. എന്റെ ശ്രമം മറ്റുള്ളവർക്കും പ്രചോദനമാകുമെങ്കിൽ…

കാട്: ഞാൻ നിന്നിൽ അഭിമാനിക്കുന്നു…. നിനക്ക് വാസസ്ഥലമായതിലും നിന്നെ ഊട്ടിയതിലും.

കുരുവി : നീ നിന്റെ ഉത്തരവാദിത്വം നിർവഹിച്ചിരിക്കുന്നു. ഞാനും നിന്നെപ്പോലെ…… (മഴപെയ്തതായും തീ അണഞ്ഞതായും സങ്കൽപ്പിക്കാം. മറ്റു മൃഗങ്ങൾ ഒത്തുചേർന്ന് തീ അണച്ചതായും സങ്കൽപ്പിക്കാം കഥ കൂട്ടുകാരുടെ ആശയത്തിനൊത്ത് അവസാനിപ്പിക്കാം).

ആശയവ്യത്യാസം

Question 1.
ഇത് പലതവണ ആവർത്തിച്ചു
ഇത് പലതവണ ആവർത്തിക്കും
ഇത് പലതവണ ആവർത്തിക്കുന്നു
അടിവരയിട്ട് പദങ്ങളുടെ പ്രയോഗം വാക്യങ്ങളുടെ ആശയതലത്തിൽ ഉണ്ടാക്കുന്ന മാറ്റം എന്ത് അതിന്റെ കാരണം ചർച്ച ചെയ്യുക ഇത്തരം പദങ്ങൾ കൂടുതൽ കണ്ടെത്തി എഴുതുക.
Answer:
പദപ്രയോഗങ്ങളുടെ വ്യത്യാസവും അർത്ഥ വ്യത്യാസങ്ങളും

വാക്യങ്ങൾ:

1. ഇത് പലതവണ ആവർത്തിച്ചു → കഴിഞ്ഞിട്ടുള്ള പ്രവൃത്തി (ഭൂതകാലം)
2. ഇത് പലതവണ ആവർത്തിക്കും → വരാനിരിക്കുന്ന പ്രവൃത്തി (ഭാവികാലം)
3. ഇത് പലതവണ ആവർത്തിക്കുന്നു → ഇപ്പോൾ നടക്കുന്നതായ പ്രവൃത്തി (വർത്തമാനകാലം)

പദപ്രയോഗം	കാലം	ആശയം
ആവർത്തിച്ചു	ഭൂതകാലം (കഴിഞ്ഞത്)	ഒരു കാര്യം വളരെവട്ടം കഴിഞ്ഞുപോയിരിക്കുന്നു
ആവർത്തിക്കുന്നു	വർത്തമാനകാലം(ഇപ്പോൾ നടക്കുകയാണ്)	പ്രവർത്തനം ഇപ്പോഴും തുടരുന്നു.
ആവർത്തിക്കും	ഭാവികാലം നടക്കാൻ പോകുന്നു	ഇപ്പോഴും പ്രതീക്ഷയുണ്ട്.

ഈ വ്യത്യാസങ്ങൾ വാചകത്തിന്റെ തീവ്രതയും സമയബോധവും മാറ്റുന്നു. ഉദാഹരണത്തിന്, ‘അവൻ പഠിച്ചു’ എന്ന് പറയുമ്പോൾ പഠനം കഴിഞ്ഞതായി സൂചനയുണ്ട്, പക്ഷേ ‘പഠിക്കുന്നു’ എന്നത് ഇപ്പോഴും പ്രവർത്തനം നടക്കുകയാണെന്നത് വ്യക്തമാക്കുന്നു. ഈ ചെറിയ വ്യത്യാസങ്ങൾ കഥയിലെ സ്ഥിതിഗതികൾ വായനക്കാരന് കൂടുതൽ വ്യക്തമായി അനുഭവപ്പെടാൻ സഹായിക്കുന്നു.

ഉദാഹരണം

തുടർപ്രവർത്തനങ്ങൾ

Question 1.
തീയണക്കാൻ ശ്രമിച്ച കുരുവിയെ പരിഹസിച്ചതാര്?
Answer:
തീയണയ്ക്കാൻ ശ്രമിച്ച് കുരുവിയെ പരിഹസിച്ചത് മഴദേവൻ ആയിരുന്നു. കുരുവിയുടെ ചെറിയ ശ്രമം കാണുമ്പോൾ മഴ ദേവൻ അത് ഫലപ്രദമല്ലെന്ന് പരിഹസിക്കുന്നു. എന്നാൽ ചെറിയ സഹായം പോലും ചെയ്യാൻ മഴദേവൻ തയ്യാറാവുന്നുമില്ല.

Question 2.
“ഞാൻ എനിക്കാവുന്നത് ചെയ്യുന്നു”-
ഈ വാക്യം ആരോട് പറഞ്ഞു? ഈ വാക്യത്തിൽ പ്രതിഫലിക്കുന്ന മാനസികാവസ്ഥയെ വിശകലനം ചെയ്യുക. സന്ദർഭം വ്യക്തമാക്കുക.
Answer:
ഈ വാക്യം കുരുവിയാണ് പറയുന്നത്. കാട്ടുതീ പടർന്നപ്പോൾ കുരുവി തന്റെ കുഞ്ഞി ചുണ്ടിൽ വെള്ളം കൊണ്ടുവന്ന് തീയിൽ തളിച്ച് തീ അണയ്ക്കാൻ ശ്രമിക്കുന്നു. അതുകണ്ട് മഴദേവൻ പരിഹസിക്കുമ്പോൾ കുരുവി ഉത്തരമായി ഈ വാക്യം പറയുന്നു തന്റെ ചെറിയ ശ്രമം ചോദ്യം ചെയ്യുന്ന മഴദേവനോട് പറയുന്നു. ‘ഞാൻ എനിക്കാവുന്നത് ചെയ്യുന്നു.’
ഇവിടെ തെളിയുന്ന മാനസികാവസ്ഥ എന്തെന്നാൽ

ഈ വാക്യം പ്രതിനിധീകരിക്കുന്നത് ഒരു വ്യക്തിയുടെ ഉത്തരവാദിത്വബോധവും ധൈര്യവുമാണ്. കുരുവി തന്റെ കഴിവിനു എന്ത് ചെയ്യാനാവുമോ അതാണ് ചെയ്യുന്നത്. മറ്റുള്ളവരുടെ പരിഹാസം അതിന്റെ ചാരുത ഇല്ലാതാക്കുന്നില്ല.

ഇത് പാഠത്തിലെ മുഖ്യ സന്ദേശമായ ‘നമ്മിൽ ഒരാൾ ഒരു ചെറിയ ശ്രമം നടത്തിയാൽ പോലും വലിയ മാറ്റത്തിന് തുടക്കമാകാം’ എന്നതിനെ പ്രതിഫലിപ്പിക്കുന്നു.

Question 3.
ആനന്ദിന്റെ എഴുത്തിൽ പ്രകടമാകുന്ന സമകാലീനതയുടെ ആത്മാവിനെ’ കുറിച്ച് പ്രതിപാദിക്കുക.
Answer:
ആനന്ദിന്റെ എഴുത്തിൽ ‘സമകാലീനതയുടെ ആത്മാവ്’ എന്നത് ആധുനിക സാമൂഹിക പ്രശ്നങ്ങളെ നേരിട്ട് അഭിമുഖീകരിക്കുന്നു (പരിസ്ഥിതി നാശം, മനുഷ്യത്വമില്ലായ്മ, യുദ്ധ ഭീഷണി, അനാസ്ഥ, നിരുത്തരവാദിത്വം). ഏകാന്തമായെങ്കിലും പ്രതിരോധം നടത്താനുള്ള വ്യക്തിയുടെ നീക്കം (കുരുവി പ്രതിനിധാനം ചെയ്യുന്ന രീതിയിൽ). ഒരു വ്യക്തിയുടെ പ്രചോദനാത്മകമായ പ്രവൃത്തികൾ വലിയ മാറ്റത്തിന് തുടക്കമാകാമെന്ന സന്ദേശം. ആനന്ദിന്റെ കഥകൾ വായനക്കാരെ ചിന്തിപ്പിക്കുന്നു, മറുപടി നിർബന്ധിക്കുന്നില്ല – മറിച്ച് വായനക്കാരൻ സ്വയം ഉത്തരമെത്തേണ്ട അവസ്ഥയിലേക്കാണ് എഴുത്ത് നയിക്കുന്നത്.

Question 4.
കുരുവിയുടെ പ്രയത്നം കണ്ട് മറ്റു മൃഗങ്ങളും കുരുവിയോടൊപ്പം ചേർന്നു എന്നിരിക്കട്ടെ കഥയുടെ അവസാനം മാറ്റി എഴുതൂ.
Answer:
കുരുവിയുടെ കൃപയും പ്രതിബദ്ധതയും കണ്ട് കാട്ടിലുള്ള മറ്റു മൃഗങ്ങൾക്ക് അവരുടെ പ്രവർത്തിയിൽ ലജ്ജ തോന്നുന്നു. മൃഗങ്ങളെല്ലാവരും വെള്ളം കൊണ്ട് തീ അണയ്ക്കാൻ ശ്രമിക്കുന്നു. ഒടുവിൽ, എല്ലാ ജീവികളുടെയും ചേർന്ന പരിശ്രമം കാട്ടുതീ അണയ്ക്കാൻ കാരണമാകുന്നു. അവരുടെ കാടിന്റെ അവർ വീണ്ടെടുത്തു. ഒരുമയുടെ ബലം അവർക്ക് മനസിലായി.
മഴദേവനും ആ ശ്രമം കാണുമ്പോൾ നാണംകെട്ട് ക്ഷമ ചോദിക്കുന്നു.
സന്ദേശം: ‘നല്ലത് ചെയ്യുന്ന ഒരാളുടെ ശ്രമം മറ്റുള്ളവരെയും ഉണർത്തുന്നു.’

അധിക അറിവിലേക്ക്

സമാന ആശയം വരുന്ന കവികളുടെയും മഹത് വ്യക്തികളുടെയും വാക്കുകൾ
‘ചെറുതെങ്കിലും തനിക്കാവുന്നത് ചെയ്യുക’ എന്ന സന്ദേശം മലയാളം സാഹിത്യത്തിലും ലോകസാഹിത്യത്തിലും പലവിധരൂപങ്ങളിലായി പ്രതിഫലിച്ചിട്ടുണ്ട്. മനുഷ്യൻ തന്റെ പരിധിയിൽ നല്ലതൊരിക്കൽ ചെയ്താൽ തന്നെ അതിന് വലിയ പ്രഭാവമുണ്ടാകാമെന്ന ചിന്ത ഉൾക്കുന്ന വചനങ്ങളും കവിതാശകലങ്ങളും ചുവടെ പങ്കുവെക്കുന്നു;

മഹത് വചനങ്ങൾ (മഹത്വമുള്ള ഉദ്ധരണികൾ).
ഗാന്ധിജി
• “Be the change you wish to see in the world.”
(നിങ്ങൾ ലോകത്തിൽ കാണാൻ ആഗ്രഹിക്കുന്ന മാറ്റം തന്നെയാവുക.)
വലിയ വ്യതിയാനങ്ങൾ ചെറുതായെങ്കിലും വ്യക്തി തലത്തിൽ തുടങ്ങണം എന്ന സന്ദേശം.

മദർ തെരേസ:
• “Not all of us can do great things. But we can do small things with great love.”
(എല്ലാവർക്കും വലിയ കാര്യങ്ങൾ ചെയ്യാൻ കഴിയില്ല. എന്നാൽ വലിയ സ്നേഹത്തോടെ ചെറുകാര്യങ്ങൾ ചെയ്യാം.)
കുരുവിയുടെ ചിന്തയോടും പ്രവർത്തിയോടും ഏറെ സാമ്യമുണ്ട്.

സ്വാമി വിവേകാനന്ദൻ:
• “Each soul is potentially divine. Serve man, serve God.”
ഓരോ മനുഷ്യനും ദിവ്യതയുള്ളവൻ. സേവനത്തിലൂടെ ലോകം മാറാം.

മലയാള കവിതാശകലങ്ങൾ:

1. നന്മ ചെയ്യുവാൻ പുറപ്പെടുക,
നിന്റെ ഉള്ളമറിഞ്ഞു നീ ഭരിക്ക…’
♦ കുമാരനാശാൻ – ‘ചിന്താവിഷ്ടയായ സീത’:
ഭവനത്തിന്റെ അകത്തു നിന്ന് തന്നെ നന്മയുടെ വിത്തിടാൻ കൃത്യമായ ഒരു ആഹ്വാനം.

2. ‘ഞാൻ മനുഷ്യനെന്നതോർത്തു
ഞാൻ മനുഷ്യരെ സ്നേഹിച്ചു…’
♦ വള്ളത്തോൾ – ‘ജാതിവെറിക്കെതിരെ’:
ഒരാളുടെ മനസ്സിനുള്ളിലെ മാറ്റം സമൂഹത്തിന് മികച്ചതാവാൻ ഇടയാക്കുന്നു.

3. ‘ഞാൻ നിശ്ശബ്ദമായി നിന്നു
ചെറുതായെങ്കിലും തണൽ
നല്കാൻ ശ്രമിച്ചു…’
♦ സുഗതകുമാരി – ‘മൂലവൃക്ഷം’:

4. വലിയൊരു ലോകം
മുഴുവൻ നന്നാവാൻ
ചെറിയൊരു സൂത്രം
ചെവിയിലോതാം ഞാൻ
‘സ്വയം നന്നാവുക’
♦ കുഞ്ഞുണ്ണി മാഷ്
കുരുവിയുടെ നിലപാടിന്റെ കാവ്യപരമായ രൂപമാണ് ഇത്

5. ‘കർമണേവാധികാരസ്തേ മാ ഫലേഷു കദാചന’
ഭഗവത് ഗീത (ചാപ്റ്റർ 2, ശ്ലോകം 47):
(ഫലമിഛിക്കാതെ കർമ്മം ചെയ്യുക.)
കുരുവി ഫലത്തെക്കുറിച്ച് ചിന്തിക്കാതെ ദൈനംദിനം ചിന്താപരമായ കർമ്മം ചെയ്യുന്നു.

മറ്റു ഭാഷകളിൽ നിന്ന് കവിതാശകലങ്ങൾ
• “If I can stop one heart from breaking,
I shall not live in vain.”
♦ എമിലി ഡിക്കിൻസൺ:
ഒരാൾക്ക് പോലും ആശ്വാസം നൽകാനാകുന്നത് ജീവിതം ഫലപ്രദമാക്കിയതായി കാണുന്നു.

കിളിമൊഴി

(കിളിമൊഴി – പക്ഷികൾക്ക് വേണ്ടി 35 ഭാഷണങ്ങൾ) ഡോ. സലിം അലി.
പരിഭാഷ എസ്. ശാന്തി

നിരീക്ഷണക്കുറിപ്പ്

Question 1.
പക്ഷിനിരീക്ഷണത്തെക്കുറിച്ചുള്ള ഡോ. സാലിം അലിയുടെ നിർദേശങ്ങൾ ശ്രദ്ധിച്ചല്ലോ. അവ കൂടി പരിഗണിച്ചുകൊണ്ട് നിങ്ങൾക്കിഷ്ടപ്പെട്ട ഒരു പക്ഷിയെ നിരീക്ഷിച്ച് കുറിപ്പ് തയ്യാറാക്കുക.
Answer:
ഡോക്ടർ സലിം അലിയുടെ നിർദ്ദേശങ്ങൾ അനുസരിച്ച് ഒരു പക്ഷിയെ ഞാൻ നിരീക്ഷിച്ചെന്നു കണക്കാക്കി തയ്യാറാക്കിയ മാതൃക കുറിപ്പാണ്. നിങ്ങൾക്ക് ഇഷ്ടമുള്ള പക്ഷിയെ ഇവിടെ ചേർത്ത് ഈ മാതൃകയുടെ അടിസ്ഥാനത്തിൽ കൂട്ടുകാരും കുറുപ്പ് തയ്യാറാക്കണേ…

പക്ഷിനിരീക്ഷണ കുറിപ്പ്

പക്ഷിയുടെ പേര്: കുഞ്ചി തത്ത (Common Green Bee eater)

1. അവലോകനം ചെയ്ത സ്ഥലം
പാലക്കാട് ജില്ലയിലെ ഒരു കൃഷി ഭൂമിയിലായിരുന്നു ഈ പക്ഷിയെ കണ്ടത്. രാവിലെ ഏകദേശം 8 മണിയായിരുന്നു സമയം. വാനിൽ വെളിച്ചവും ചുറ്റും നിശബ്ദതയും ഉണ്ടായിരുന്നു.

2. ദൃശ്യവിവരണം
വലുപ്പം: ഏകദേശം ഒരു ചെറുതത്തയുടെ വലിപ്പം (16 – 18 സെ.മീ.).
നിറം: പച്ച നിറം ആധാരമായി കാണപ്പെടുന്നു. തലയിൽ ചെറിയ വെള്ള ചുവപ്പ് നിറമുള്ള പാലിളക്കം. കഴുത്ത് ചുറ്റി കറുത്ത വര.
ശരീരരൂപം: അതിസുന്ദരമായി നീളമുള്ള ചിറകും വാൽപ്പക്ഷ ത്തേയും കാണാം. രണ്ടു വാടികൾ കുറച്ച് നീളത്തിൽ നീളിയി രിക്കുന്നു.
കൊക്ക്: കുറച്ച് നീളമുള്ളതും വളഞ്ഞതും കറുത്ത നിറത്തി ലുള്ളതും.
കണ്ണുകൾ: ചെറുതായി ചുവപ്പു നിറം പതിച്ച കാഴ്ച.
കാൽ: ചെറുതും കറുത്തതും.
ഇരിപ്പിടം: വരമ്പത്ത് നാട്ടിയ ഒരു തൂണിന്മേൽ ഇരിക്കുകയായിരുന്നു.
കണ്ടത്: ഒറ്റയ്ക്കായിരുന്നു പക്ഷി.
നടപ്പുകൾ: വീണ്ടും വീണ്ടും വരമ്പത്ത് തൂണിൽ നിന്ന് പറന്നു ചെറു കീടങ്ങൾ പിടിച്ച് തിരികെ തൂണിലേയ്ക്ക് വരികയായിരുന്നു.
ശബ്ദം: ചെറുതായി ചിര് ചിര്’ പോലുള്ള ശബ്ദം ഉരിയുന്നു.

4. ആവാസ സ്ഥലം
ഈ
പക്ഷിയെ കൃഷിഭൂമികൾ, തുറന്ന ശുദ്ധവായുവുള്ള ഇടങ്ങൾ, വയൽ പാടങ്ങൾ, മരക്കൊമ്പുകൾ എന്നിവിടങ്ങളിൽ സാധാരണ യായി കാണാം.

5. നിരീക്ഷണ അഭിപ്രായം
കുഞ്ചി തത്തയെ നിരീക്ഷിക്കുന്നത് വളരെ രസകരമായ അനുഭവമാണ്. നാട്ടുവേലി തത്ത എന്നും ഇതിനെ പേരുണ്ട്. അതിന്റെ തെളിഞ്ഞ പച്ച നിറം പച്ചപ്പ് നിറഞ്ഞ പശ്ചാത്തലത്തിൽ ആകർഷകമായി നിറഞ്ഞുനിൽക്കുന്നു. തത്സമയം തന്നെ പറന്ന് കീടങ്ങൾ പിടിക്കുന്ന അതിന്റെ കൃത്യത ഉറ്റുനോക്കിയാൽ അതിന്റെ മനോഹാരിതയെ ഏറെ മികവോടെ കാണാം. ശാന്തമായ ഒരു രാവിലെ ഈ പക്ഷിയെ കാണാനായതിൽ ഞാൻ സന്തോഷവാനാണ്.

പക്ഷി നിരീക്ഷണം

വ്യവസ്ഥാധിഷ്ഠിതമായ പക്ഷിനിരീക്ഷണത്തിന് ഇന്ത്യയിൽ അടിസ്ഥാനമിട്ട ആളാണ് സാലിം അലി (സാലിം മുഇസുദ്ദീൻ അബ്ദുൾ അലി, നവംബർ 12, 1896 – ജൂലൈ 27, 1987) അദ്ദേഹത്തിന്റെ നിരീക്ഷണങ്ങൾ, ഭാരതത്തിലെ ജനങ്ങളിൽ പക്ഷിനിരീക്ഷണത്തിനും, പ്രകൃതി സ്നേഹത്തിനും അടിത്തറയിട്ടു. പക്ഷിനിരീക്ഷണ ശാസ്ത്രത്തെക്കുറിച്ചും പക്ഷികളെക്കുറിച്ചും സലിം എഴുതിയ ഗ്രന്ഥങ്ങൾ വിജ്ഞാനപ്രദവും പ്രസിദ്ധവുമാണ്. ഇവയിൽ കേരളത്തിലെ പക്ഷികളെ പറ്റിയെഴുതിയ ഗ്രന്ഥവും ഉൾപ്പെടും. ഒരു കുരുവിയുടെ പതനം’ അദ്ദേഹത്തിന്റെ ആത്മകഥയാണ്. പക്ഷിമനുഷ്യൻ എന്നും ഇദ്ദേഹം അറിയപ്പെടുന്നു

Class 8 Malayalam Adisthana Padavali Notes Unit 1 കനിവും കരുതലും

താഴെ കാണുന്ന ചിത്രങ്ങൾ ‘കനിവും കരുതലും’ എന്ന അധ്യായത്തിന്റെ ഭാഗമായി ഉൾപ്പെടുത്തിയതാണ്. ഇവ തമ്മിൽ ഉള്ള തിരിച്ചറിയലുകളും പ്രതിപാദ്യവും മനസ്സിലാക്കുന്ന പാഠഭാഗങ്ങളാണ് ഈ യൂണിറ്റിൽ പഠിക്കാൻ ഉള്ളത്. കുരുവിയും കാട്ടുതീയും, കൊച്ചു ദേവദാരു, പെരുമഴയത്ത് എന്നീ കഥകളുടെ ആകെ തുകയാണ് ഈ ചിത്രങ്ങൾ.

ചിത്രം 1: കാനനസൗന്ദര്യം – ചിത്രകാരൻ: മുരളി നാഗപ്പുഴ
(ഒ.എൻ.വി കുറുപ്പിന്റെ ഭൂമിക്ക് ഒരു ചരമഗീതം എന്ന പുസ്തകത്തിന്റെ കവർ ചിത്രം കൂടിയാണിത്)

മുരളി നാഗപ്പുഴയുടെ ചിത്രങ്ങൾ പച്ചപ്പും സാധാരണവും ഗ്രാമീണതയും അതിനോടൊപ്പം നിറങ്ങൾ ചാർത്തിയ കൗതുകങ്ങളും തിങ്ങി നിൽക്കുന്നുണ്ടായിരിക്കും അതുകൊണ്ടുതന്നെ അന്താരാഷ്ട്രതലത്തിൽ അവാർഡുകൾ നേടിയ ചിത്രങ്ങളാണ് മുരളി നാഗപ്പുഴയുടേത്.

ഈ ചിത്രം ശാന്തവും പച്ചപ്പും നിറഞ്ഞ ഒരു വനപ്രദേശം കാണിക്കുന്നു. കുട്ടികൾ വനത്തിൽ ശാസ്ത്രീയമായി പഠിക്കുകയും ആനന്ദിക്കുകയും ചെയ്യുന്നു.ആകാശത്ത് പറക്കുന്ന പക്ഷികൾ, തഴുകുന്ന മരങ്ങൾ, നിറഞ്ഞ ചെടികൾ എന്നിവ പ്രകൃതിയുടെ സമൃദ്ധിയും നിമിഷികതയും ചൂണ്ടിക്കാട്ടുന്നു. പ്രകൃതിയോട് സ്നേഹത്തോടെ സമീപിക്കുക, അതിൽ നിന്ന് പഠിക്കുക എന്നതാണ് ഈ ചിത്രത്തിന്റെ പ്രധാന താത്പര്യം.

ചിത്രം 2:- ചിത്രകാരൻ: സബീനബി
ആഗോളതാപനത്തെക്കുറിച്ചുള്ള ഒരു അന്താരാഷ്ട്ര കാർട്ടൂൺ (റഷ്യൻ എക്കോളജിക്കൽ മൂവ്മെന്റ് സംഘടിപ്പിച്ച) മത്സരത്തിൽ നാമനിർദ്ദേശം ചെയ്യപ്പെട്ട ആർട്ടിസ്റ്റ് സിബി ഷിബുവിന്റെ ചിത്രം.

ഈ ചിത്രത്തിൽ വരൾച്ച വിണ്ടുപോയ ഭൂമിക്ക് നടുവിലൂടെ രണ്ട് ആളുകൾ നടന്നു പോവുകയാണ്, അവരുടെ കൈയിൽ വിലയേറിയ ഒരു ജലത്തുള്ളിയുണ്ട്. തിളങ്ങുന്ന ആ ഒറ്റ തുള്ളി വെള്ളം, ഒരൊറ്റ വെള്ളതുള്ളിയെ ഏറ്റവും വിലപ്പെട്ടതായി കണക്കാക്കേണ്ടി വരുന്ന ആ നിമിഷം ഓർത്ത് നോക്കൂ. പ്രകൃതിയോട് അനാദരവ് കാട്ടുമ്പോൾ അതിന്റെ പ്രത്യാഘാതം എങ്ങനെയായിരിക്കും എന്നതിന്റെ മുന്നറിയിപ്പാണ് ഈ ചിത്രം.

ആദ്യ ചിത്രം പ്രകൃതിയോട് സ്നേഹപരമായ അനുഭാവവും സംരക്ഷണവും നൽകുമ്പോൾ രണ്ടാം ചിത്രം പ്രകൃതിദുരന്തത്തിന്റെ ദാരുണ ഫലങ്ങളെയും കാണിക്കുന്നു. ഈ രണ്ട് ചിത്രങ്ങളിലൂടെ മനുഷ്യന് പ്രകൃതിയോടുള്ള ഉത്തരവാദിത്വം വ്യക്തമാക്കുന്നു.