Classify each of the following as exothermic or endothermic: a. CH₄(g) + 2O₂(g) →∆ CO₂(g) + 2H₂O(g) + 802kJ

Exothermic reactions are chemical processes that release energy, usually in the form of heat, to the surroundings. This energy release occurs because the total energy of the products is lower than that of the reactants. A common example is the combustion of fuels, where energy is released as heat and light.

Endothermic reactions absorb energy from their surroundings, resulting in a decrease in temperature of the immediate environment. In these reactions, the energy of the products is higher than that of the reactants. Photosynthesis is a classic example, where plants absorb sunlight to convert carbon dioxide and water into glucose.

Enthalpy change (ΔH) is a measure of the heat content of a system during a chemical reaction at constant pressure. A negative ΔH indicates an exothermic reaction, while a positive ΔH signifies an endothermic reaction. In the given reaction, the release of 802 kJ suggests that it is exothermic, as energy is being released to the surroundings.