What makes a change spontaneous, entropy and the second law, Gibbs energy and the sign of ΔG, the effect of temperature, and the link between ΔG and equilibrium.
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Created by StemPy LabA spontaneous change happens on its own, once it is started. Giving out heat helps, but some changes that take in heat are spontaneous too. Entropy, a measure of how spread out matter and energy are, completes the story: in every spontaneous change the total entropy of the system and the surroundings rises.
Gibbs energy, , puts enthalpy and entropy into one quantity. At constant temperature and pressure a change is spontaneous when is negative, at equilibrium when it is zero, and not spontaneous when it is positive. The signs of and decide how temperature changes the answer.
The standard Gibbs energy change of a reaction fixes its equilibrium constant: . A negative means is more than 1, so products are favoured. At , every of changes tenfold.
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