IB Physics Heat and Internal Energy
/A tutorial sheet on the words heat and internal energy, concepts that are often confused in examination answers.
- The internal energy of an object is the sum of the potential energies of molecular interaction and the kinetic energies of molecular movement.
- The internal energy of an object can be changed by doing work on it or by supplying heat to it.
- Heat is energy that is transmitted between two objects at a different temperature.
- By doing work and supplying heat the change in internal energy is given by the first law of thermodynamics. ΔU = Δq + W.
- When a paddle wheel does work in churning water the energy supplied did not become heat but became internal energy of the water due to its rise in temperature. This energy may be transmitted to the surroundings as heat energy and will become internal energy of the surroundings.
