Materials: Metals and Non-Metals - Class 8 : NCERT Exercise Questions



Q.1 Which of the following can be beaten into thin sheets?
(a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen
Sol.  (a) Zinc

Q.2 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.
Sol. (c) Generally, metals are ductile.

Q.3 Fill in the blanks:
(a) Phosphorus is very ___________ non-metal.
(b) Metals are ___________ conductors of heat and ___________.
(c) Iron is ___________ reactive than copper.
(d) Metals react with acids to produce ___________ gas.
Sol. (a) Phosphorus is very reactive non-metal.
(b) Metals are good conductors of heat and electricity.
(c) Iron is more reactive than copper.
(d) Metals react with acids to produce Hydrogen gas.

Q.4  Mark ‘T’ if the statement is true and ‘F’ if it is false.
(a) Generally, non-metals react with acids.                                     ( )
(b) Sodium is a very reactive metal.                                               ( )
(c) Copper displaces zinc from zinc sulphate solution.                  ( )
(d) Coal can be drawn into wires.                                                   ( )
Sol. (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)

Q.5 Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.

Properties

Metals

Non-metals

1. Appearance

2. Hardness
3. Malleability
4. Ductility
5. Heat Conduction
6. Conduction of Electricity

Sol.

Properties

Metals

Non-metals

1. Appearance

Lustrous

Dull

2. Hardness

Hard

Soft
3. Malleability

Malleable

Non-malleable

4. Ductility

Ductile

Non-ductile

5. Heat Conduction

Good Conductor

Bad Conductor

6. Conduction of Electricity

Good Conductor

Bad Conductor

Q.6 Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Sol. (a) Aluminium foils are used to wrap food items because aluminium is highly malleable metal. Hence, it can be easily be beaten into thin sheets. In addition, it does not react with food.
(b) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity.
(c) Copper cannot displace zinc from its salt solution because the reactivity of zinc is higher than copper. And only a metal of higher reactivity can displace a metal of lower reactivity from its salt solution.
(d) Sodium and potassium are stored in kerosene because they are highly reactive and catch fire when kept in open.

 Q.7 Can you store lemon pickle in an aluminium utensil? Explain.
Sol. No, we cannot store lemon pickle in an aluminium utensil because aluminium is a metal and lemon is an acid, so they will react with each other to release hydrogen gas. And so the pickle will get spoiled.

Q.8 In the following Table some substances are given in Column I. In Column II some uses are given. Match the items in column I with those in Column II.

Column I

Column II

(i) Gold

(a) Thermometers

(ii) Iron

(b) Electric wire

(iii) Aluminium (c) Wrapping food
(iv) Carbon (d) Jewellery
(v) Copper (e) Machinary
(vi) Mercury (f) Fuel

Sol.

Column I

Column II

          (i) Gold

       (d) Jewellery

         (ii) Iron

       (e) Machinary

         (iii) Aluminium        (c) Wrapping food
         (iv) Carbon        (f) Fuel
         (v) Copper        (b) Electric wire
        (vi) Mercury        (a) Thermometers

Q.9 What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Sol. (a) When dilute sulphuric acid is poured on a copper plate, copper reacts with sulphuric acid to release hydrogen gas.
    Cu           +                  H2SO4               →          CuSO4            +            H2
(Copper)                  (Sulphuric Acid)            (Copper Sulphate)       (Hydrogen Gas)
(b) When iron nails are placed in copper sulphate solution, iron will displace copper from copper sulphate solution with the blue colour of copper sulphate fading.
   Fe         +           CuSO4            →          FeSO4         +       Cu
(Iron)            (Copper Sulphate)         (Iron Sulphate)        (Copper)

 

Q.10 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?
(b) Write down word equations of all the reactions taking place in this process.
Sol.  (a) To find the nature of the gas, add some water in the test tube. Now, shake the test tube well covering it properly. Test the solution with blue and red litmus paper. It will be observed that blue litmus turns red which means the nature of gas is acidic.
(b) When a piece of charcoal is burnt, it reacts with oxygen to release carbon dioxide gas.
      C           +          O2   →              CO2                   

(Charcoal)        (Oxygen)       (Carbon Dioxide)

Q.11 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?
Sol. Gold jewellery is polished by dipping them in an acidic solution. When polished, the outer layer of jewellery gets dissolved and the inner layer gets visible which is shinny. As there is loss of upper layer, there is loss in weight of the gold jewellery.



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