The difference between exothermic and endothermic reactions is found in their names: "endo" means to draw into itself, whereas "exo" means to emit. All chemical reactions either release or use energy, which can be in the... More »

Evaporation is an endothermic process. These types of reactions occur when the temperature of the system decreases and the surroundings gain energy. Endothermic reactions end up with an overall positive heat of reaction. More »

Sublimation is an endothermic process, which means that energy must be added to a substance to facilitate the process. Sublimation is the term that describes a solid substance turning directly into a gas. More »

Melting is a process involving absorption of energy, which means that it is endothermic. A process whereby energy is released into the atmosphere or surrounding region is called an exothermic process. More »

Combustion reactions can only be exothermic. In chemical reactions, old bonds are broken to form new ones. Depending on the energy difference between broken and formed bonds, the total reaction energy is either positive ... More »

The difference between exergonic and exothermic reactions is that energy is released to the surroundings in an exergonic reaction. When an exothermic reaction occurs, the energy released to the surroundings is heat energ... More »

The difference between an atom and a molecule is that molecules are composed of two or more atoms. Atoms are the smallest units of matter and, when they join chemically, they form a molecule. More » Science Chemistry Atoms & Molecules