What type of reaction absorbs energy as it occurs?

The type of reaction that absorbs energy as it occurs is an endothermic reaction. In these reactions, the system takes in heat energy from its surroundings, which can lead to a drop in temperature of the surroundings. This energy absorption is essential for the reaction to proceed, as it typically involves breaking bonds that require more energy than is released when new bonds form.

Endothermic reactions are common in various chemical processes, such as photosynthesis in plants, where sunlight is absorbed to transform carbon dioxide and water into glucose and oxygen. This illustrates the principle that energy is needed for the reaction to occur, rather than being released as in exothermic reactions.

On the contrary, exothermic reactions release energy, usually in the form of heat, during the process. Catalytic reactions involve the use of a catalyst to increase the reaction rate without being consumed in the process, while synthetic reactions are those that involve the combination of smaller molecules to form larger ones but do not inherently define energy absorption or release.