Entropy of fusion

The entropy of fusion (symbol SM0 or ΔFUSS ) of a chemical substance is the change in entropy of the substance at change of state from solid to liquid. Does the value of the entropy of fusion on the amount of one mole, one also speaks of the molar entropy of fusion (symbol SM0m ).

The unit of measurement of the molar entropy of fusion, J / (K · mol ).

As a measure of disorder in a system, one can imagine that this disorder increases with increasing temperature - as water molecules, which are initially present in the ice crystal in a certain order, dissolve by heating the liquid water out of this association until it according to boiling almost completely independently move around each other.

A formulation of the third law of thermodynamics states: For every pure, crystallized in an ideal order fabric is the entropy at absolute zero the same. It is these substances at T = 0, the entropy is zero.

Why can molar Schmelzentropien specify in absolute values ​​. However, be, depending on the system under consideration, selected other zero points for the entropy of fusion. In electrochemical measurements in aqueous ionic solutions containing, for example, has one proton, the entropy of fusion to zero.

Entropy of fusion and melting enthalpy are related by the equation Tm = AH /? S.