Give reasons for the following:
$(i)$ All decomposition reactions are endothermic reactions.
$(ii)$ Colour of copper sulphate solution changes when an iron nail is dipped in it.
$(iii)$ Respiration is an exothermic reaction.

(N/A) $(i)$ Decomposition reactions require energy in the form of heat,light,or electricity to break down the reactants,meaning energy is absorbed.
$(ii)$ Iron is more reactive than copper. When an iron nail is dipped in a copper sulphate solution,iron displaces copper from the solution to form iron sulphate,which is light green in colour.
$(iii)$ During respiration,glucose $(C_6H_{12}O_6)$ combines with oxygen in the cells of our body to produce carbon dioxide,water,and energy. Since energy is released during this process,it is considered an exothermic reaction.