Materials: Metals and Non-Metals

Q58. What happens when iron nails are placed in copper sulphate solution?

Ans. Iron being more reactive displaces copper from copper sulphate. In this reaction, the blue color of copper sulphate fades and there is deposition of copper on the iron nail.

Fe(Iron) + CuSO₄(Copper sulphate) → FeSO₄(Iron sulphate) + Cu(Copper)

Q59. Have you ever seen a greenish deposit on the surface of copper vessels? What is that?
Or
Why a greenish deposit is found on copper vessels in rainy season?
Or
Why do copper vessels develop a greenish layer when exposed to moist air?

Ans. When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The green material is a mixture of copper hydroxide (Cu(OH)₂) and copper carbonate (CuCO₃). The following is the reaction

2Cu+H₂O+CO₂+O₂→Cu (OH)₂ + CuCO₃

Q60. What happens when dilute sulphuric acid is poured on a copper plate?

Ans. Metals react with acids and produce hydrogen gas that burns with a ‘pop’ sound. Copper is below hydrogen in reactivity series. Thus, copper does not react with dilute sulphuric acid but it reacts with sulphuric acid on heating. Hence, no reaction will take place when dilute sulphuric acid is poured on a copper plate.

Q61. State some of the chemical properties of non-metals.
Or
What are the chemical properties of a non-metal?

Ans. Chemical properties of non-metals

                          i.        Non-metals react with oxygen to produce non- metallic oxides which are acidic in nature.

                         ii.        Generally, non-metals do not react with water.

                        iii.        Generally, non-metals do not react with acids.

Q62. One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Ans. In order to polish the gold ornament, it is to be dipped into a liquid called aquaregia (a mixture of hydrochloric acid and nitric acid). On getting dissolved in the environment of aquaregia, the outer layer of gold dissolves and an inner shiny layer appear. The dissolving of the layer causes a reduction in the weight of the jewelry.

Q63. State some of the physical properties of non-metals.

Ans. Physical properties of non-metals

                         i.        They are brittle.

                        ii.        They are not ductile.

                       iii.        They are poor conductors of heat and electricity.

                       iv.        They are dull.

                        v.        They are not strong.

                       vi.        They are not sonorous.

         vii.        Most of the solid non-metals are quite soft.

Q64. What are the uses of non-metal?
Or
What is the importance of non-metals?

Ans. Uses of non-metal

                          i.        Non-metal essential for our life which all living beings inhale during breathing,

                         ii.        Non-metals used in fertilisers to enhance the growth of plants,

                        iii.        Non-metal used in water purification process,

                        iv.        Non-metal used in the purple coloured solution which is applied on wounds as an antiseptic,

                         v.        Non-metals used in crackers.

Q65. State some of the chemical properties of metals.
Or
What are the chemical properties of a metal?

Ans. Chemical properties of metals

                          i.        On burning, metals react with oxygen to produce metal oxides which are basic in nature.

                         ii.        Some metals react with water to produce metal hydroxides and hydrogen gas.

                        iii.        Metals react with acids and produce metal salts and hydrogen gas.

                        iv.        Some metals react with bases to produce hydrogen gas.

                         v.        More reactive metals displace less reactive metals from their compounds in aqueous solutions.

Q66. Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.