Assessment and Qualifications Alliance (AQA) GCSE Chemistry Paper 1 Practice Exam

The correct answer is burning fuels, as this process is a quintessential example of an exothermic reaction. During combustion, fuels react with oxygen to produce energy, typically in the form of heat and light. This release of energy occurs because the bonds formed in the products (carbon dioxide and water) are stronger than the bonds broken in the reactants (the fuel and oxygen), resulting in a net release of energy to the surroundings.

In contrast, while heating water requires the addition of energy to raise its temperature and thus is an endothermic process, mixing acids and bases can produce heat but is not as universally characteristic of exothermic reactions as burning fuels. Evaporating liquids, on the other hand, is also an endothermic process, as this requires energy input to overcome intermolecular forces. Therefore, burning fuels is the most widely recognized process that is commonly involved in exothermic reactions.