On heating calciu

(a) Heating of calcium carbonate to get calcium oxide and carbon dioxide is a chemical change as new substance with different composition and chemical properties are formed.

CaCO₃ (Calcium carbonate) → CaO (Calcium oxide) + CO₂ (Carbon dioxide)
(b) Acidic and basic solutions can be prepared by dissolving the products of the above process in water.

When CaO dissolves in water it forms calcium hydroxide which is basic solution.

CaO+H₂O → Ca(OH)₂ (basic solution)

When CO₂(g) dissolves in water it forms carbonic acid which is an acidic solution.

CO₂ + H₂O→H₂CO₃ (acidic solution)