As described above, when describing chemical potential, one has to say "relative to what".

However, some systems contain important variables that are equivalent to the chemical potential.

Here, the chemical potential has been defined as the energy per molecule.

As a result, the chemical potential of the black body photon gas is zero.

At 0 C. this "chemical potential" of the ice and the water are equal to each other.

But the "chemical potential" of the ice remains the same.

Remember, I said that "chemical potential" increases with increasing temperature.

There is discontinuity in the chemical potential at each such point.

The generalized force component of this pair is the chemical potential.

The chemical potential is like a force which pushes an increase in particle number.