Write the chemical equation of the reaction with an example in which a change in temperature takes place.

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.

Calcium oxide reacts vigorously with water to produce:

Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
$(a)$ Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
$(b)$ Ethanol is burnt in air to form carbon dioxide,water and releases heat.

In which of the following chemical equations,the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Complete and balance the following chemical equations:
$(i)$ $CaCO_{3} + HCl \longrightarrow$
$(ii)$ $Al + HCl \longrightarrow$
$(iii)$ $MnO_{2} + HCl \longrightarrow$