How do endothermic and exothermic reactions differ?

Endothermic and exothermic reactions are categorized based on their heat exchange with the surroundings. Endothermic reactions absorb heat from their environment, resulting in a temperature drop in the surroundings, while exothermic reactions release heat, which increases the temperature of the surroundings.

The distinction is critical in understanding how different chemical processes impact temperature and energy transfer. For example, photosynthesis is an endothermic reaction because it requires energy (in the form of sunlight) to convert carbon dioxide and water into glucose and oxygen. Conversely, combustion reactions, such as the burning of wood or fossil fuels, are exothermic because they release heat and light energy into the environment, making the surroundings warmer.

Thus, the correct answer accurately reflects the fundamental nature of these reactions: endothermic reactions require and absorb heat energy, whereas exothermic reactions produce and release heat energy.