# Why do molecules in a gas not generally arrange themselves at the distance of minimum potential energy?

Why do molecules in a gas not generally arrange themselves at the distance of minimum potential energy?
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Abagail Stephenson
The state of equilibrium is characterised by a minimum in free energy F=U−TS (Helmholtz for simplicity), not a minimum in potential energy.
What this means is that while the system is indeed attempting to minimise the potential energy U, it is simultaneously trying to maximise the entropy S. The balance, i.e. which term dominates, is determined by the temperature T.
At high temperatures, entropy (which favours spaced out, randomly disordered atoms) dominates. This can also be understood from an atomistic perspective: at high temperatures, the atoms are randomly jiggling at high velocities and therefore have a tendency to break any bonds that form.