Which evidence suggests that energy changed during ethanol combustion?

The production of heat during the combustion of ethanol indicates a change in energy. During combustion, chemical energy stored in the bonds of ethanol molecules is released as heat and light through an exothermic reaction. This release of energy is a fundamental characteristic of combustion reactions, as reactants such as ethanol and oxygen interact, leading to the formation of products like carbon dioxide and water, along with the release of significant thermal energy.

The generation of heat can be measured and felt, signifying that energy has transitioned from the chemical form to thermal energy. This transition is what makes combustion processes useful for applications such as heating and powering engines. Other choices, such as the formation of water droplets or changes in flame color, can indicate aspects of the reaction but do not directly measure the energy change relative to the heat produced. Weight changes in the container may occur, but they don't provide direct evidence of energy transformation during the reaction.