NCERT Solution Metals and non-metals Class 10

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In-text QuestionsGive an example of a metal which

  1. is a liquid at room temperature.
    Answer: Mercury
  2. can be easily cut with a knife.
    Answer: Sodium
  3. is the best conductor of heat. 
    Answer: Silver
  4. is a poor conductor of heat.
    Answer: Lead

2. Explain the meanings of malleable and ductile.
Answer: Malleable: Metals can be beaten into thin sheets and hence they are called malleable.

Ductile: Metals can be drawn into thin wires and hence they are called ductile.

A malleable metal is also ductile and these properties are present in almost all the metals.

3. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is a highly reactive metal and it reacts vigorously with water even at room temperature. Sodium is so reactive that it can even react with the atmospheric moisture. This reaction is highly exothermic which produces fire as well. Sodium is kept immersed in kerosene oil to prevent its reaction with water and to prevent accidental fire.

4. Write equations for the reactions of

  1. iron with steam
    Answer: 

3Fe + 4H2O —à Fe3O4 + 4H2

  1. calcium and potassium with water
    Answer:

Ca + 2H2O —à Ca(OH)2 + H2

2K + 2H2O —à 2K(OH)2 + H2

5. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

Metal Iron(II) sulphate Copper(II) sulphate Zinc sulphate Silver nitrate
A No reaction Displacement    
B Displacement   No reaction  
C No reaction No reaction No reaction Displacement
D No reaction No reaction No reaction No reaction

Use the table above to answer the following questions about metals A, B, C and D.

  1. Which is the most reactive metal?
    Answer: B is the most reactive metal
  2. What would you observe if B is added to a solution of Copper(II) sulphate?
    Answer: When B is added to copper (II) sulphate solution, it displaces copper.
  3. Arrange the metals A, B, C and D in the order of decreasing reactivity.
    Answer: B > A > C > D

6. Which gas is produced when diluting hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4

Answer: When a reactive metal reacts with the dilute hydrochloric acid, hydrogen gas is produced. The chemical equation for the reaction between iron and dilute hydrochloric acid is as follows:

Fe + H2SO4 —à FeSO4 + H2

7. What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
Answer: Zinc displaces iron from iron (II) sulphate solution because zinc is more reactive than iron. This reaction can be shown by the following equation:

Zn + FeSO4 —à ZnSO4 + Fe

1. Answer the following questions: Write the electron-dot structures for sodium, oxygen and magnesium.

  1. Answer: Electronic dot structure of Na(11)

Electronic dot structure of O (8):

Electronic dot structure of Mg (12):

Show the formation of Na2O and MgO by the transfer of electrons. 
Answer: Electron dot structures of sodium oxide and

magnesium oxide are as follows

8. What are the ions present in these compounds?
Answer: In both the compounds; oxide ions are present. The sodium ion is present in sodium oxide, while magnesium ion is present in magnesium oxide.

9. Why do ionic compounds have high melting points?
Answer: The force of attraction in ionic bonds is very strong and it is difficult to overcome that force. Hence, ionic compounds have high melting points.

10. Define the following terms.

  1. Mineral
    Answer: A substance which naturally occurs in the earth’s crust and has a uniform composition is called a mineral.
    1. Ore
      Answer: A mineral from which a substance can be profitably extracted is called an ore.
    1. Gangue
      Answer: The impurities present in an ore are called gangue.

11. Name two metals which are found in nature in the free state.
Answer: Silver and gold

12. What chemical process is used for obtaining a metal from its oxide?
Answer: For obtaining a metal from its oxide, we need to use reduction. This process is carried out by heating the metal oxides; usually with a reducing agent.

13. Metallic oxides of zinc, magnesium and copper were heated one by one with zinc, magnesium and copper. In which cases will you find displacement reactions taking place?
Answer: Displacement reaction takes place only when zinc oxide is heated with magnesium. And No reaction takes place in other cases.

14. Which metals do not corrode easily?
Answer: Metals which are at the bottom of the reactivity series do not corrode easily, e.g. copper, silver and gold.

15. What are alloys?
Answer: A homogenous mixture of two or more than two metals or a metal and a non-metal is called an alloy.

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