Class 10 Chemistry

Metals and Non-metals

NCERT In Text Solutions

Give an example of a metal which

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

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.

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.

Write equations for the reactions of

• iron with steam
  
  Answer: 3Fe + 4H₂O ⇨ Fe₃O₄ + 4H₂
• calcium and potassium with water
  
  Answer: Ca + 2H₂O ⇨ Ca(OH)₂ + H₂
  
  2K + 2H₂O ⇨ 2K(OH)₂ + H₂

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.

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

• Which is the most reactive metal?
  
  Answer: B is the most reactive metal
• 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.
• Arrange the metals A, B, C and D in the order of decreasing reactivity.
  
  Answer: B > A > C > D