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Laws of Thermodynamics


This document describes the laws of thermodynamics, which have proven to be valid after centuries of experimental observations.

The First Law of Thermodynamics

Energy cannot be created or destroyed, it can only be converted between different forms.

Another way to state the first law is that the energy change of a system must equal the energy transferred to or from the surroundings.

The Second Law of Thermodynamics

Heat cannot be converted to work in a cyclical process with 100% efficiency.

Another way to state the second law is that the entropy of the universe is always increasing.

The Third Law of Thermodynamics

The entropy of a perfect crystalline substance at zero Kelvin is defined to be zero.

The Zeroth Law of Thermodynamics

Two systems that are in equilibrium with a third system must also be in equilibrium with each other.

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