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

The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 6 Metals and Non Metals Important Questions ensure conceptual clarity.

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

Metals and Non Metals Class 8 Important Questions

Question 1.
Which metal has the highest malleability?
a) Aluminium
b) Iron
c) Copper
d) Gold
Answer:
d) Gold

Question 2.
Which of the following metals is the most electrically conductive?
a) Aluminium
b) Silver
c) Copper
d) Gold
Answer:
b) Silver

Question 3.
Find the odd one out
a) Aluminium
b) Sodium
c) Potassium
d) Lithium
Answer:
a) Aluminium (Others are soft metals)

Question 4.
Find and fill in the relationship
The shining of metal surfaces: Metallic lustre
The ability to produce sound when struck on the surface: ____________
Answer:
Sonority

Question 5.
What is the basic substance formed when magnesium oxide dissolves in water?
Answer:
Magnesium Hydroxide

Question 6.
Why do iron appliances in houses near the sea rust quickly?
Answer:
Iron rusts quickly due to the presence of salt (sodium chloride) in the air.

Question 7.
What metal is present in haemoglobin in the blood?
Answer:
Iron

Question 8.
Which of the following metals is subject to corrosion the fastest?
a) Gold
b) Aluminium
c) Iron
d) Sodium
Answer:
d) Sodium

Question 9.
Generally metals can be hammered and flattened into thin sheets. This characteristic property of metals is known as _____________ .
Answer:
Malleability

Question 10.
Write aluminium, copper, gold, and silver in the order of decreasing electrical conductivity.
Answer:
Silver > Copper > Gold > Aluminium

Question 11.
Metals can be drawn and stretched into wires. This property is called ductility. Write any two cases where ductility is used.
Answer:

• Filament of bulb
• Electric wires
• Gold ornaments

Question 12.
Which properties of metals are utilised in the following cases?
a) Iron is used to make weapons.
b) Aluminium is used to make food packaging.
Answer:
a) Hardness
b) Malleability

Question 13.
Give examples of non-metals that are added to metals to make alloys.
Answer:

1. Carbon
2. Phosphorous

Question 14.
Alloys generally have high melting points. Give examples of metals with low melting points.
Answer:

1. Gallium
2. Caesium

Question 15.
Which properties of metals are used in the following situations?
a) Copper is used to make bells.
b) Tungsten is used to make the filament of a light bulb.
Answer:
a) Sonority – the ability to produce a specific sound when struck with a hard object.
b) Ductility – the ability to be formed into very thin wires.

Question 16.
What factors increase the corrosion of iron?
Answer:

• Presence of air
• Presence of moisture
• Presence of salt

Question 17.
Copper nails are used instead of iron nails in coastal areas. Why?
Answer:
In coastal areas, there is a presence of salt in the air. Iron rusts quickly in the presence of air and moisture. Therefore, copper nails are used instead of iron nails.

Question 18.
Classify the following as metals or non-metals.
• Carbon
• Phosphorous
• Sulphur
• Gallium
• Helium
• Sodium
• Caesium
Answer:

Metals	Non-Metals
Sodium Gallium Caesium Calcium	Carbon Sulphur Phosphorous Helium

Question 19.
Magnesium reacts with oxygen in the air to form magnesium oxide.
a) Write the chemical equation for this reaction.
b) What is the product of magnesium oxide dissolved in water?
Answer:
a) 2Mg + O₂ → 2MgO
b) Magnesium Hydroxide

Question 20.
Write any two metals found in the human body and their importance.
Answer:
Iron – is an important component of haemoglobin in the blood.
Calcium – strengthens bones and teeth. Regulates blood pressure.

Question 21.
Compare and list any three properties of metals and non-metals.
Answer:

Metals	Non metals
Generally, they are hard.	Generally, they are less hard.
They exhibit sonority.	They don’t exhibit sonority.
Generally, they are electrically conductive.	Not thermal conductors.

Question 22.
What are the properties of gold that make it suitable for making jewellery?
Answer:
a) Gold is used to make jewellery by alloying it with copper or silver.
b) Malleability, metallic lustre, corrosion resistance, ductility.

Question 23.
Give reasons for the following:
a) The handles of electrical tools and cooking utensils are made of non-metals.
b) Metals like sodium, potassium etc. are stored in kerosene.
c) Pickles and curds are not stored in metal containers.
Answer:
a) Electric tools and cookware are made of metals. Metals are good conductors of electricity and heat. Therefore, their handles are made of non-metals such as wood, plastic, rubber, etc. to ensure safe handling without injury.

b) Sodium and potassium are very reactive metals. They react rapidly with air and moisture and are destroyed. They are stored in kerosene to avoid contact with the environment.

c) Acids are present in sour foods like pickles and curd. Acids can react with metals to form other substances and can corrode metal containers.

Question 24.
a) What is an alloy?
b) What are the benefits of alloying metals?
c) Give examples of alloys.
Answer:
a) Metals are combined with other metals or non-metals to make alloys.

b) 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.

c) Stainless steel, brass, bronze

Question 25.
a) What is corrosion of metals?
b) Suggest ways to prevent corrosion of metals
Answer:
a) Metals react with various elements in the atmosphere to form compounds. This process is palled corrosion.

b)

• Paint metal surfaces.
• Apply oil and grease.
• Apply non-metallic coatings such as rubber and plastic.
• Convert into alloys.

Question 26.
Take three test tubes. Put a rust-free and shiny iron nail in each of them. Place a wet cloth in the first test tube, and add a cloth soaked in salt water to the second test tube.. Iron nails should be fully immersed in these three test tubes. Take anhydrous calcium chloride or quicklime in the third test tube. All three test tubes should be closed immediately with a cork after adding the materials.
What will be the observation after a few days? Write the reason for the observation in each test tube.
Answer:
Test tube 1: The nail in the test tube is rusty
This is due to the presence of air and moisture in the test tube.
Test tube 2: The nail in the test tube is rustier. In addition to the presence of air and moisture, the presence of salt increases the rate of rusting.
Test tube 3: The nail in the test tube is not rusty. The nail absorbs the moisture inside the test tube. In the absence of moisture, the rusting process does not take place.

Question 27.
Observe the picture.

Calcium chloride is taken in a test tube. A smooth iron nail is moistened and passed through a cork and the test tube is closed.
a) What will be the observation after a few days?
b) Write the reason for the observation.
c) What is the conclusion drawn from this?
Answer:
a) The part of the nail inside the test tube is not rusted. The part of the nail outside the test tube is rusted. The calcium chloride absorbs the moisture inside the test tube. Therefore, the iron does not rust.
b) The presence of water and moisture outside the test tube causes the iron to rust rapidly.
c) The presence of water and air affects the rusting of iron.

Question 28.
a) How is soda water made?
b) Write the chemical equation for this reaction.
c) What is observed when blue litmus paper is dipped in soda water? What is the reason?
Answer:
a) Soda water is made by dissolving carbon dioxide in water under high pressure.
b) CO₂ + H₂O → H₂CO₃
c) Soda water is carbonic acid. The presence of acid turns blue litmus red.

Question 29.
Observe the diagram of the electric circuit.

a) Which of the following objects will make the bulb light up if you connect it to the part marked PQ?
• Rolled aluminum foil
• Rubber band
• Glass rod
• Plastic wire
• Iron nail
• Silver necklace
b) What is the reason for this difference?
Answer:

Bulb Glows	The bulb does not glow
Rolled Aluminium foil Iron nail Silver necklace	Glass rod Rubber band Plastic wire

b) Aluminium, iron, and silver are electrical conductors. Glass, rubber, and plastic are not electrical conductors.

Question 30.
Select and arrange the items from columns B and C that match those in section A.

A	B	C
Aluminium	Sonority	Filaments
Tungsten	Thermal Conductivity	Church Bells
Copper	Ductility	Cooking utensils

Answer:

A	B	C
Aluminium	Thermal Conductivity	Cooking utensils
Tungsten	Ductility	Filaments
Copper	Sonority	Church bells