Identify the type of reactions in each of the following reactions:
$(i)$ $Zn + H_{2}SO_{4} \longrightarrow ZnSO_{4} + H_{2}$
$(ii)$ $CaO + H_{2}O \longrightarrow Ca(OH)_{2}$

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.

State whether the following statement is true or false:
Keeping food in airtight containers helps to slow down oxidation.

Write balanced chemical equations for the following reactions:
$(i)$ Calcium carbonate on reaction with hydrochloric acid gives calcium chloride,water and carbon dioxide.
$(ii)$ Nitrogen reacts with hydrogen under pressure to form ammonia.
$(iii)$ Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.

Write true or false for the following statement: On heating the crystals of ferrous sulphate,the colour changes from green to grey.

Name the type of reaction for the following:
$(i)$ Vegetable matter changing into compost.
$(ii)$ Burning of natural gas.