NCERT SOLUTIONS CLASS 10 CHAPTER 3

Question 1. Give an example of a metal which

(i) is a liquid at room temperature.

(ii) can be easily cut with a knife.

(iii) is the best conductor of heat.

(iv) is a poor conductor of heat.

Answer

1. Mercury
2. Sodium

• Silver

1. Mercury and Lead

Question 2.

Explain the meanings of malleable and ductile.

Malleable means that the substance can be beaten into thin sheets. For example, most of the metals are malleable.

Ductile means that the substance can be drawn into wires. For example, most of the metal are ductile.

 

Question 3.

Why is sodium kept immersed in kerosene oil?

Answer Sodium is a highly reactive element. It reacts vigorously with oxygen with a pop sound to catch fire. Hence to avoid this sodium is kept in kerosene.

 

Question 4.

Write equations for the reactions of

(i) iron with steam

(ii) calcium and potassium with water

Answer

1. 3Fe (s) + 4H₂O (g) → Fe₃O₄ (aq) + 4H₂
2. Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g) + Heat
3. 2K (s) + 2H₂O (l) → 2KOH (aq) + H₂ (g) + Heat

 

Question 4.

Which gas is produced when dilute hydrochloric acid is added to a

reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.

Answer When dilute hydrochloric acid is added to a reactive metal, Hydrogen gas is evolved as a result.

When Iron reacts with dilute H₂SO_4, Iron (II) sulphate is formed with the evolution of hydrogen gas.

Fe (s) + H₂SO₄ (aq) → FeSO₄ (aq) + H₂ (g)

 

Question 5.

What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.

Metal zinc is added to iron (II) sulphate then it will diplace iron from iron sulphate solution as shown by the given reaction.

Zn (s) + FeSO₄ (aq) → ZnSO₄ (aq) + Fe (s)

Question 7.

Why do ionic compounds have high melting points?

Answer Ionic compounds have strong electrostatic forces of attraction between the ions. Thus huge amount of energy is required to overcome these forces. This is the reason why ionic compounds have high melting points.

 

Question 8.

Define the following terms.

(i) Mineral (ii) Ore (iii) Gangue

Answer

1. Mineral: the naturally occurring compounds of elements are known as Mineral.
2. Ore: Mineral’s form which metals can be extracted profitably are known as Ore.

• Gangue: The impurities found in the ore like sand, rocks etc are called as gangue.

 

Question 9.

Name two metals which are found in nature in the free state.

Answer the metals which are present at the bottom of the reactivity series are mostly found in free state. For example Silver, gold and platinum.

 

Question 10.

What chemical process is used for obtaining a metal from its oxide?

Answer

Metal can be obtained from its oxide by the process of reduction.

2HgO (s) → 2Hg (l) + O₂ (g)