First law of thermodynamics

Definition

The First Law of Thermodynamics states that energy cannot be created or destroyed in an isolated system, only transformed from one form to another. It is also known as the law of energy conservation.

5 Must Know Facts For Your Next Test

1. The mathematical representation of the First Law of Thermodynamics is $\Delta U = Q - W$, where $\Delta U$ is the change in internal energy, $Q$ is the heat added to the system, and $W$ is the work done by the system.
2. In an isolated system, the total energy remains constant over time.
3. This law applies to all types of thermodynamic systems, including closed and open systems.
4. Heat added to a system can increase its internal energy or do work on the surroundings.
5. The First Law does not specify the direction of processes; it only quantifies the energy changes.

Review Questions

• What does the equation $\Delta U = Q - W$ represent?
• How does adding heat to a system affect its internal energy and work done?
• Can energy be created or destroyed according to the First Law of Thermodynamics?

Related terms

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

Heat: A form of energy transfer between systems or objects with different temperatures, moving from high temperature to low temperature.

Work: Energy transfer that occurs when an external force moves an object or changes its physical state.