Which type of reaction absorbs thermal energy from its surroundings?

An endothermic reaction is one that absorbs thermal energy from its surroundings during the reaction process. This absorption of heat results in a drop in the temperature of the surroundings, as the energy is taken in to drive the reaction forward. A common example is the process of photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen.

In contrast, exothermic reactions release energy, usually in the form of heat, into the surroundings. This results in an increase in temperature, which is the opposite of what happens in endothermic reactions. Decomposition and combination reactions can be either exothermic or endothermic, depending on the specific substances involved and the nature of the reaction. However, the defining characteristic of an endothermic reaction is its requirement of energy from the environment, making it the correct choice in this case.