Chemical energy

Chemical energy is energy associated with the arrangement of atoms and electrons in substances. Chemical reactions transfer energy as bonds break and form, often releasing or absorbing heat or work.

Chemical reaction: A process that rearranges atoms by breaking and forming chemical bonds. Reactions transfer energy when reactants and products differ in chemical energy.
Chemical bond: An attractive interaction that holds atoms or ions together in a substance. Bond formation and bond breaking accompany changes in chemical energy.
Combustion: A rapid reaction with an oxidizer that commonly releases heat and light. Combustion converts fuel’s chemical energy into thermal energy and often radiation.
Thermal energy: The portion of a system’s internal energy associated with the random motion and interactions of its microscopic constituents. Reaction heat can raise thermal energy, but the two quantities are not interchangeable.
Hydrogen combustion: The reaction of hydrogen with oxygen to form water, releasing energy under common conditions. It illustrates chemical energy release in a reaction whose product bonds are especially stable.
Enthalpy: A thermodynamic state function equal to a system’s internal energy plus pressure times volume. At constant pressure, its change tracks heat released or absorbed by many reactions.
Potential energy: Energy associated with the arrangement of interacting objects or particles. Chemical energy is a molecular-scale form of energy tied to arrangement.
Electrochemical cell: A device in which redox reactions convert chemical energy into electrical energy or the reverse. Its separated reactions channel chemical energy into electric current.
Nuclear energy: Energy associated with the structure and interactions of atomic nuclei. Nuclear transformations involve the nucleus, unlike ordinary chemical changes in electrons and bonds.
Photosynthesis: A process by which organisms use light energy to synthesize organic compounds from carbon dioxide and water. It stores incoming light energy in chemical products rather than releasing it from fuel.

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