# Explain Mass and Energy with definition.

21 Points
13 years ago

MASS AND ENERGY

The science of chemistry was built up by assuming that in chemical reactions, energy and mass are each conserved. In 1905, Einstein showed that, as a consequence of his special theory of relativity, mass can be considered to be another form of energy. Thus the law of conservation of energy is really the law of conservation of mass-energy.

In a chemical reaction, the amount of mass that is transferred into other forms of energy )or vice versa) is such a tiny fraction of the total mass involved that there is no hope of measuring the mass change with even the best laboratory balance. Mass and energy truly seem to be separately conserved. In a nuclear reaction, however, the energy released is often about a million times greater than in a chemical reaction, and the change in mass can easily be measured. Taking mass-energy transfers into account where nuclear reactions are involved becomes a matter of necessary laboratory routine.

Mass and energy are related by what is certainly the best-known equation in physics namely,

E=mc2
In which E is the energy equivalent (called the mass energy) of mass m, and c is the speed of light.

The amount of energy lying dormant in ordinary objects is enormous. The energy equivalent of the mass of a penny, for example, would cost over a million dollars to purchase from your local utility company. The mass equivalents of some energies are equally striking. The entire annual U.S. electrical energy production, for example, corresponds to a mass of only a few hundred kilograms of matter (stones, potatoes, library, books, anything).