Changes

:allows us to define the concept of [[temperature]], by stating that "''Two systems in thermal [[equilibrium]] with a third one are in thermal equilibrium with each other''". This law is called "zeroth" because it was only formulated after the three others, but is actually more fundamental, and hence deserves a lower number.

:allows us to define the concept of [[temperature]], by stating that "''Two systems in thermal [[equilibrium]] with a third one are in thermal equilibrium with each other''". This law is called "zeroth" because it was only formulated after the three others, but is actually more fundamental, and hence deserves a lower number.

;[[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]] and [[work]] are transfers of energy.

; [[Second Law of Thermodynamics|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.