thermodynamiske

Thermodynamics is the branch of physics that studies energy, heat, work, and how these quantities relate to temperature and the state of matter. The term thermodynamiske is the Danish and Norwegian adjective for anything pertaining to thermodynamics.

It considers systems and their surroundings, differentiating state variables such as pressure, volume, temperature, and composition. Many properties are state functions; their values depend only on the current state, not on the path taken to reach it. Energy transfer occurs as heat or work across boundaries.

The subject is governed by four laws. Zeroth law establishes thermal equilibrium and the notion of temperature. First law expresses energy conservation via ΔU = Q − W. Second law introduces entropy and implies that natural processes are irreversible and sets limits on efficiency. Third law states that the entropy of a perfect crystal approaches zero at absolute zero.

Common mathematical tools include thermodynamic potentials—internal energy U, enthalpy H, Helmholtz free energy F, and Gibbs free energy G—obtained by Legendre transforms and useful for describing processes at constant T, P, or V. Statistical thermodynamics connects macroscopic quantities to microscopic states.

Applications span heat engines, refrigerators, chemical reactions, phase transitions, and material science. The field underpins many engineering disciplines and provides the theoretical framework for energy systems and process design.