What happens when sulfur trioxide reacts with water?

Which of the following is(are) an endothermic process(es)?
$(i)$ Dilution of sulphuric acid
$(ii)$ Sublimation of dry ice
$(iii)$ Condensation of water vapours
$(iv)$ Evaporation of water

$(a)$ Consider the following chemical equation:
$Fe_{2}O_{3} + 2Al \rightarrow Al_{2}O_{3} + 2Fe$
Name two categories in which you can place this reaction.
$(b)$ Define the term 'Oxidation' of a substance and name the substance oxidised and the oxidising agent in the above reaction.

Crystals of copper sulphate are heated in a test tube for some time. What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process?

What is the colour of $FeSO_{4} \cdot 7H_{2}O$ crystals? How does this colour change upon heating? Give the balanced chemical equation for the change.

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.