NCERT Solutions for class 10 Science Chapter 3:Metals and Non-metals

NCERT Solutions for class 10 Science Chapter 3 Exercise Question

Question 1

Which of the following pairs will give displacement reactions?

(a) NaCl solution and copper metal

(b) MgCl₂ solution and aluminium metal

(c) FeSO₄ solution and silver metal

(d) AgNO₃ solution and copper metal

Answer

Option d) AgNO₃ solution and copper is correct answer. Copper displace the silver

Cu(s) + 2AgNO₃ (aq) → Cu(NO₃)₂ (aq) + 2Ag (s)

Question 2

Which of the following methods is suitable for preventing an iron frying pan from rusting?

Applying grease
Applying paint
Applying a coating of zinc
All of the above

Answer

(c) Applying a coat of Zinc

Question 3

An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be

(a) Calcium

(b) Carbon

(c) Silicon

(d) Iron

Answer

option (a) i.e Calcium.

Question 4

Food cans are coated with tin and not with zinc because

(a) Zinc is costlier than tin.

(b) Zinc has a higher melting point than tin.

(c) Zinc is more reactive than tin.

(d) Zinc is less reactive than tin.

Answer

c) Zinc is more reactive than tin

Question 5

You are given a hammer, a battery, a bulb, wires and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?

(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.

Answer

a) Metals show malleable property we can be easily drown into sheets by hitting with hammer. On the other hand non-metals they are non-malleable if we beat with hammer they break sample
b) Metals are good conductors of electricity when we connect it into circuit using battary , switch wire and bulb the bulb start glows.then the sample are metal Similarly non-metals are bad conductors of electricity if the bulb not glows means samples are non metal

Question 6

What are amphoteric oxides? Give two examples of amphoteric oxides

Answer

The Oxides which react with both acids and bases to produce salt and water are known as amphoteric oxides.
Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂+ H₂O
ZnO + 2HCl → ZnCl₂ + H₂O
ZnO + 2NaOH → Na₂ZnO₂ + H₂O

Question 7

Name two metals which will displace hydrogen from dilute acids, and two metals which will not.

Answer

The two metals which will displace Hydrogen from dilute acids are Zinc and Magnesium because they are very reactive metals. And copper, silver are the metals which will not replace Hydrogen from dilute acids because these metals are less reactive.

Question 8

In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?

Answer

We take
Pure metal M at Cathode
Impure metal M at Anode
A water soluble salt of metal M at Electrolyte

Question 9

Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in the figure.

(a) What will be the action of gas on

(i) dry litmus paper?

(ii) moist litmus paper?

(b) Write a balanced chemical equation for the reaction taking place.

Solution: a) When sulphur powder is heat in the air sulphur dioxide is formed.

(i) Sulphur dioxide does not show action on dry litmus paper.

(ii) Sulphur dioxide turn the moist litmus paper from blue to red

(b) S(s) + O₂(g) → SO₂(g)

Question 10

State two ways to prevent the rusting of iron.

Answer

Two ways to prevent the rusting of iron are following

galvanisation

Greasing

Question 11

What type of oxides are formed when non-metals combine with oxygen?

Answer

When non-metals combine with oxygen it forms acidic or neutral oxides.Suphur form an acidic oxide ,Hydrogen form an neutral oxide.

Question 12

Give reasons

(a) Platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium and lithium are stored under oil.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction

Answer

(a) Platinum, gold and silver are used to make jewellery because they are very less reactive , luster malleable and ductile in nature and also show high corrosion .

(b) Sodium, potassium and lithium are stored under oil to prevent their reaction with air as they are very reactive and catch fire when exposed to air.

(c) Aluminium forms a non-reactive layer of aluminium oxide all over its surface in presence of air . This layer prevents aluminium to react with other substances. That’s why aluminium is used to make cooking utensils.

(d) It is easy to extract metal form its oxide rather than from their carbonates or sulphides.

Question 13

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

Answer

Copper reacts with air to form copper carbonate.Lemon or tamarind juice contain acids Lemons juice contain citric acid and termarind contains tartaric acids these acids dissolve the coating of copper oxide or basic copper carbonate present on the surface of tarnished copper vessels and make them shining red brown again

Question 14

Differentiate between metal and non-metal on the basis of their chemical properties.

Answer

Question 15

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Answer

Goldsmith dipped the gold ornaments in Aqua regia solution. It is the mixture of concentrated Hydrochloric acid and concentrated nitric acid. Aqua-regia dissolved a considerable amount of gold from gold bangles and reduced their weight drastically.

Question 16

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

Answer

Copper is used to make hot water tanks and not steel because copper does not reacts with water or steam whereas iron reacts with steams to corrode the tank.