Page 21 - NCERT Science Class 10 English Medium

12. Write one equation each for decomposition reactions where energy is supplied in
the form of heat, light or electricity.
13. What is the difference between displacement and double displacement reactions?
Write equations for these reactions.
14. In the refining of silver, the recovery of silver from silver nitrate solution involved
displacement by copper metal. Write down the reaction involved.
15. What do you mean by a precipitation reaction? Explain by giving examples.
16. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
17. A shiny brown coloured element ‘X’ on heating in air becomes black in colour.
Name the element ‘X’ and the black coloured compound formed.
18. Why do we apply paint on iron articles?
19. Oil and fat containing food items are flushed with nitrogen. Why?
20. Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity

Group Activity

Perform the following activity.
n Take four beakers and label them as A, B, C and D.
n Put 25 mL of water in A, B and C beakers and copper sulphate solution in beaker D.
n Measure and record the temperature of each liquid contained in the beakers above.
n Add two spatulas of potassium sulphate, ammonium nitrate, anhydrous copper
sulphate and fine iron fillings to beakers A, B, C and D respectively and stir.
n Finally measure and record the temperature of each of the mixture above.
Find out which reactions are exothermic and which ones are endothermic in nature.

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