What type of reaction releases heat into the surroundings?

An exothermic reaction is one that releases heat into the surroundings. This type of reaction occurs when the total energy of the products is lower than the total energy of the reactants, resulting in the excess energy being released as heat. This can often be observed in chemical reactions such as combustion, where substances react with oxygen to produce heat and light, a common example being burning fuels.

In contrast, endothermic reactions absorb heat from the surroundings, leading to a decrease in the temperature of the environment during the process. Isothermal refers to processes that occur at a constant temperature, which is not directly related to the release or absorption of heat. Phase changes can involve either exothermic or endothermic reactions, depending on the specific change being undergone (e.g., freezing of water is exothermic, while melting is endothermic). Thus, identifying exothermic reactions specifically highlights their unique characteristic of heat release, making them distinct from the other types mentioned.