(a) An endothermic process is one in which heat is absorbed during the reaction.

For example, burning carbon in the presence of oxygen produces carbon dioxide and releases a significant quantity of heat.

C (s) + O₂ (g) →CO₂ + Heat

(b) The oxidation reaction is exothermic. Exothermic reactions release energy in the form of light or heat, while oxidation is a reaction in which oxygen reacts with other elements.

(c) In the reaction of copper oxide with hydrogen to produce copper and water, oxidation and reduction operate side by side. The reaction can be represented as follows:-

CuO + H₂→ Cu + H₂O