Metals and Non Metals Class 8 Questions and Answers Notes Basic Science Chapter 6 Kerala Syllabus

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.