Science Class 8 – Chapter 4 – Materials: Metals and Non-Metals – NCERT Exercise Solution ( Question-Answer)

Q1.Which of the following can be beaten into thin sheets?

(a) Zinc      (b) Phosphorus     (c) Sulphur      (d) Oxygen

Answer- (a) Zinc

Q2. Which of the following statements is correct?

(a) All metals are ductile.

(b) All non-metals are ductile.

(c) Generally, metals are ductile.

(d) Some non-metals are ductile.

Answer- (c) Generally, metals are ductile.

Q3. Fill in the blanks.

(a) Phosphorus is a very ___________non-metal.

Answer – reactive

(b) Metals are _____________conductors of heat and ___________.

Answer – good, electricity

(c) Iron is ______________reactive than copper.

Answer – more

(d) Metals react with acids to produce __________gas.

Answer – hydrogen

Q4. Mark ‘T’ if the statement is true and ‘F’ if it is false.

(a) Generally, non-metals react with acids.               (F)❌

(b) Sodium is a very reactive metal.                          (T) ✔

(c) Copper displaces zinc from zinc sulphate solution.      (F).❌

(d) Coal can be drawn into wires.                     (F)❌

Q5. Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.

Answer –

Q6. Give reasons for the following.

(a) Aluminum foils are used to wrap food items.

Answer – Because it does not react with food items. It is soft. It is malleable and easily beaten in sheets to make its foil for wrapping food items etc.

(b) Immersion rods for heating liquids are made up of metallic substances.

Answer – Because metal is a good conductor of heat and electricity. When the electric current passed through the metallic rod, it gets hot very soon and warms the water.

(c) Copper cannot displace zinc from its salt solution.

Answer – Zinc is more reactive than copper. So, copper can’t displace it.

Cu + ZnSO4 ——-> No reaction.

(d) Sodium and potassium are stored in kerosene.

Answer – Sodium and potassium are stored in Kerosene. Because sodium and potassium are so highly reactive. They can easily catch fire even when in contact with air.

Q7. Can you store the lemon pickle in an aluminum utensil? Explain.

Answer – No, we can’t store the lemon pickle in an aluminium utensil because aluminium is metal and lemon pickle is an acid. So, the metal reacts with acid and produce salt and hydrogen and the pickle will be spoiled.

Q8. Match the substances given in Column A with their uses given in Column B.

Answer-

Q9. What happens when –

(a) Dilute sulphuric acid is poured on a copper plate?

Answer – H2SO4 (sulphuric acid) + Cu (copper) —-> CuSO4 ( Copper sulphate) + H2 (Hydrogen) when concentrated sulphuric acid.

No reaction takes place with dilute sulphuric acid because copper is very less reactive.

(b) Iron nails are placed in a copper sulphate solution?

Write word equations of the reactions involved.

Answer – Fe + CuSO4 —-> FeSO4 + Cu

Iron is more reactive than copper so, Fe replaces copper from solution.

Q10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.

(a) How will she find the nature of the gas?

Answer – She finds the nature of the gas with the help of wet litmus paper. When litmus paper is in contact with the gas its colour will change. If blue litmus paper turns in red, it is acidic in nature. If litmus paper turns to blue it is basic in nature.

(b) Write down word equations of all the reactions taking place in this process.

Answer –

(i) C + O2 —-> CO2

(ii) CO2 + H2O —-> H2CO3 (carbonic acid)

( turn blue litmus red)

Q11. One day Reeta went to a Jeweller’s shop with her mother. Her mother gave an 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?

Answer – For the purpose to polish the gold jewellery, jeweller dipped the jewellery in a liquid called aqua regia ( a mixture of hydrochloric acid and nitric acid). When gold jewellery dipped into an acid solution, the outer layer of gold dissolved and inner layer appears.

The dissolving of layer causes a reduction in the weight of the jewellery.