Law of Conservation of Matter and Energy
Definition and meaning of Law of Conservation of Matter and Energy in chemistry.
The Law of Conservation of Matter and Energy states that the total amount of mass and energy in an isolated system remains constant, though they may change forms. It combines the classical laws of conservation of mass and conservation of energy, recognizing that mass and energy are interconvertible.
In more detail
Historically, chemistry operated under the conservation of mass, asserting that matter cannot be created or destroyed in a chemical reaction. However, Albert Einstein's formulation of mass-energy equivalence demonstrated that mass can be converted into energy and vice versa. While the mass change in ordinary chemical reactions is so minuscule that it is essentially undetectable, this combined law is crucial in nuclear chemistry, where substantial amounts of mass are converted into enormous quantities of energy during fission and fusion. In any closed system, the sum of all mass and energy always remains perfectly balanced.
Key facts
| Field | Physical Chemistry |
|---|---|
| Core Principle | Total mass-energy is constant |
| Key Equation | E = mc^2 |
In a nuclear reactor, the fission of uranium-235 transforms a tiny fraction of the atom's mass into a massive amount of usable energy, illustrating the conservation of matter and energy.
Frequently asked questions
Does the mass of a system change during a regular chemical reaction?
Technically yes, because energy is released or absorbed, but the mass change is so small that it is completely negligible and undetectable in typical chemistry.