Energy conservation

Definition

Energy conservation is the principle stating that the total energy of an isolated system remains constant. It implies that energy can neither be created nor destroyed, only transformed from one form to another.

5 Must Know Facts For Your Next Test

1. The First Law of Thermodynamics is a statement of energy conservation.
2. In thermodynamic processes, internal energy change is equal to heat added to the system minus work done by the system: $\Delta U = Q - W$.
3. Isolated systems have constant total energy, while closed systems exchange only energy (not matter) with surroundings.
4. In cyclic processes, the net change in internal energy over one complete cycle is zero.
5. The concept of enthalpy ($H = U + PV$) incorporates both internal energy and work done by pressure-volume changes in a system.

Review Questions

• What does the First Law of Thermodynamics state about energy?
• In a thermodynamic process, how is the change in internal energy calculated?
• How does an isolated system differ from a closed system in terms of energy and matter exchange?

Related terms

Internal Energy: The total energy contained within a thermodynamic system, including kinetic and potential energies at the molecular level.

Heat (Q): Energy transfer due to temperature difference between a system and its surroundings.

Work (W): Energy transfer resulting from force applied over distance or changes in volume against external pressure.