The study of energy and its transformations is known as thermodynamics.

Energy is commonly defined as the capacity to do work or to transfer heat.

Work is energy used to cause an object with mass to move.

Heat is energy used to cause the temperature of an object to increase.

Kinetic energy is the energy of motion, represented by the equation:

E_k = ¹/₂ mv²

Atoms and molecules have mass and are in motion,
therefore they have kinetic energy.

Potential energy is energy of position, based on the relative position of one object with another.

Gravitational potential energy is represented by the equation:

E_p = mgh

Gravity, near the surface of the Earth, accelerates all objects at a rate equal to the gravitational constant, g, 9.8 m/s².

Modern work with the gravitational theory began with Galileo Galilei in the 1590s and continued with Sir Isaac newton in the 1680s. Gravity is an important force for large objects, but in the submicroscopic world of atoms it is negligible.