The First Law of Thermodynamics in Physics

The first law is conservation of energy written for systems that heat up, cool down, expand and get squeezed. It says that the internal energy of a gas can only change in two ways, by heat crossing the boundary or by work being done at the boundary, and nothing else counts. Every relation on this page is either a way of measuring one of those two transfers or a case where one of them is forced to zero. Fix the volume and no work is possible. Insulate the walls and no heat is possible. Complete a full cycle and the internal energy must come back to where it started. The blocks also cover the three ways heat travels, conduction, radiation, and the specific and latent heats that decide how much energy a temperature or a state change actually costs.