Identify the type of reactions in each of the following reactions:
$(i)$ $CaCO_{3} \xrightarrow{\text{Heat}} CaO + CO_{2}$
$(ii)$ $AgNO_{3}(aq) + NaCl(aq) \longrightarrow AgCl(s) \downarrow + NaNO_{3}(aq)$

Write one equation each for decomposition reactions where energy is supplied in the form of heat,light,or electricity.

Describe an activity to show a decomposition reaction in which light is used to decompose a reactant. Write the chemical equation of the reaction and state its one use.

Which one is a chemical change: Electrolysis of water or Sodium chloride exposed to sunlight?

What happens when a piece of $Zn$ metal is added to $CuSO_4$ solution?

Observe the following diagram and answer the questions that follow:
$(i)$ Identify the gases evolved at anode and cathode.
$(ii)$ Why are the amounts of gases collected in the two test tubes not of the same volume?
$(iii)$ What type of reaction is this?
$(iv)$ Why should we use salt water?