Law of Conservation of Energy
Definition and meaning of Law of Conservation of Energy in chemistry.
The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. In an isolated system, the total amount of energy remains constant.
In more detail
This fundamental principle governs all chemical reactions and physical processes. During a chemical reaction, energy stored in chemical bonds is converted into other forms such as heat, light, or kinetic energy, but the total energy of the system plus surroundings remains unchanged. Exothermic reactions release energy while endothermic reactions absorb it. The first law of thermodynamics is a direct application of energy conservation in chemistry.
Key facts
| Field | Physical Chemistry |
|---|---|
| Core principle | Energy cannot be created or destroyed |
| Forms converted in reactions | Chemical, thermal, light, kinetic |
| Related fundamental law | First law of thermodynamics |
When hydrogen gas burns in oxygen to form water (2H2 + O2 → 2H2O), the chemical energy in the H-H and O=O bonds converts into thermal energy and light. The total energy before the reaction equals the total energy after it, though in different forms.
Frequently asked questions
Can energy be created in a chemical reaction?
No. Energy is converted between forms but never created. An exothermic reaction releases chemical energy as heat or light, not new energy.
How does energy conservation apply to endothermic reactions?
Endothermic reactions absorb energy from their surroundings, converting it from thermal or other forms into chemical potential energy stored in new bonds.