Internal Energy and Particle Motion

This lesson covers internal energy and its relationship to particle motion as required by the AQA GCSE Physics specification (4.3.2). Understanding internal energy is essential for explaining how heating a substance affects its temperature and state. Internal energy is a key concept that links the particle model to thermal energy transfers.

---

What Is Internal Energy?

The internal energy of a system is the total kinetic energy and potential energy of all the particles that make up the system.

Internal energy = total kinetic energy + total potential energy of all particles

• Kinetic energy of particles: the energy associated with the movement (vibration, rotation, translation) of particles. The faster the particles move, the greater their kinetic energy.
• Potential energy of particles: the energy associated with the forces of attraction (bonds) between particles. This depends on the distances between particles and the strength of the forces holding them together.