Julius Mayer a German physicist first stated the law of conservation of energy in 1842. He discovered that chemical reactions created heat and work, and then more heat was made. He determined this through the experiment where heat evolved in the compression of gas but he didn 't know heat could be explained in terms of kinetic energy. The law of conservation of energy states that the amount of energy is constant, meaning energy cannot be created or destroyed. Mayer’s discovery was not highly considered and James joule’s work gained more attention.

Between 1839 and 1850 while studying the electric motors, Joule discovered that heat that travelled across the wire was directly proportional to the amount of work done by dynamo. He named it the caloric theory. Both Mayer and Joule’s discovery concluded that work is numerically equivalent to the amount of heat. The law of conservation of energy is known as the first law of thermodynamics, the study of work and energy. During the second half of 19th century Thompson and few other scientist including Maxwell, Boltzmann, Clausius and Rankine continued research developing this idea. The science of thermodynamics and kinetic theory became more common, with law of conservation of energy as first law and law of dissipation of energy as the second law.
The law of conservation of energy is a basic law in physics along with conservation of momentum and conservation of mass. The first law of thermodynamic states that energy cannot be