Changes

;[[The First Law of Thermodynamics]]

;[[The First Law of Thermodynamics]]

:states that [[energy]] is conserved and that [[heat]] is a form of energy.

:states that [[energy]] is conserved and that [[heat]] is a form of energy.

;The [[Second Law of Thermodynamics]]

; [[Second Law of Thermodynamics|The Second Law of Thermodynamics]]

:states (in one of its various formulations) that [[entropy]] in an isolated system cannot decrease, and that ''irreversible processes'' can only make it increase.<ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref> An equivalent formulation states that heat cannot spontaneously flow from a cooler body to a hotter body.

:states (in one of its various formulations) that [[entropy]] in an isolated system cannot decrease, and that ''irreversible processes'' can only make it increase.<ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref> An equivalent formulation states that heat cannot spontaneously flow from a cooler body to a hotter body.

;[[The Third Law of Thermodynamics]]

;[[The Third Law of Thermodynamics]]

:also known as ''Nernst's Law'', states that it is not possible to bring any system to the [[absolute zero]] of temperature in a finite number of operations.

:also known as ''Nernst's Law'', states that it is not possible to bring any system to the [[absolute zero]] of temperature in a finite number of operations. Also stated as follows: The entropy of a perfect crystal at absolute zero is zero.

Also stated as follows: The entropy of a perfect crystal at absolute zero is zero.

These laws tell us to what constraints ''any'' system is subject. For example, it allows us to calculate the maximum possible efficiency of an [[engine]] once we know the temperature at which it operates.

These laws tell us to what constraints ''any'' system is subject. For example, it allows us to calculate the maximum possible efficiency of an [[engine]] once we know the temperature at which it operates.