termodünaamikat

Termodünaamikat, or thermodynamics, is a branch of physics that studies the relationships between heat, work, energy, and the state of physical systems. It addresses how energy is transferred, transformed, and stored, and how macroscopic properties such as temperature, pressure, and volume relate to one another. The field applies to gases, liquids, and solids, and to closed, open, or isolated systems.

The zeroth law defines thermal equilibrium and underpins the concept of temperature: if two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other. The first law expresses energy conservation: ΔU = Q − W, where ΔU is the change in internal energy, Q is heat added to the system, and W is work performed by the system on its surroundings. Different sign conventions exist in chemistry and physics.

The second law introduces entropy and the direction of processes. For any isolated system, entropy tends to increase; heat engines operating between two reservoirs have an upper efficiency given by Carnot’s limit η ≤ 1 − Tc/Th. The third law states that the entropy of a perfect crystal approaches zero as temperature approaches absolute zero, making absolute zero unattainable in finite steps.

Thermodynamics uses state functions that depend only on current state, not path, such as internal energy U, enthalpy H, Helmholtz free energy F, and Gibbs free energy G. These potentials help predict equilibrium, phase transitions, and the direction of chemical reactions under various constraints (constant S, V, T, P, etc.).

In addition to macroscopic thermodynamics, statistical mechanics provides microscopic explanations for entropy and temperature, linking atomic behavior to bulk properties. Applications span engines, refrigerators, chemical processes, material science, and environmental and aerospace engineering, making thermodynamics a foundational tool in science and engineering.