Cambridge O Level Physics · Syllabus 5054 · Thermal Physics
Internal Energy
What is Internal Energy?
Internal energy is the total energy stored by all the particles of an object, made up of the kinetic energy of their random motion and the potential energy associated with the forces between them; raising an object's temperature increases its internal energy, but internal energy also depends on the mass and the state of the substance.
This definition is part of the Thermal Physics chapter in Cambridge O Level Physics.
Common mistakes with Internal Energy
- 2. “Temperature is the total energy in an object.” Why it is wrong: temperature takes no account of how much substance is present. A spark and a bonfire can be at similar temperatures with vastly different energy. Corrected model: temperature indicates the average kinetic energy of the particles; the total is the internal energy, which also depends on mass and state. Exam-safe: “Temperature indicates the average kinetic energy of the particles, whereas internal energy is the total kinetic and potential energy of all of them.”
Questions students ask about Internal Energy
What is the difference between temperature and internal energy?
Temperature indicates the average kinetic energy of a substance's particles, while internal energy is the total kinetic and potential energy of all the particles combined. A hot spark and a large bonfire can have similar temperatures despite very different internal energy, because internal energy also depends on the mass and state of the substance. Raising an object's temperature always increases its internal energy, but internal energy also changes during a change of state, when the temperature stays constant.