# What is Enthalpy Conceptually?

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1. Feb 6, 2016

### Cole

So I understand that enthalpy is energy. But what energy specifically? Is enthalpy heat energy? Is it the energy that bonds atoms together and that's why it can either be released or absorbed? Or is that what Gibbs free energy is?

I'm trying to make sense of the equation:

ΔG=ΔH-TΔS

Conceptually, how is enthalpy different from Gibbs free energy?

Thanks!

2. Feb 6, 2016

### Staff: Mentor

Enthalpy is just a convenient parameter to work with in solving certain kinds of problems. It doesn't have a fundamental significance (in my judgment) like internal energy has. It is just H = U + PV, and this group arises often in many problems and analyses. My advice is not to spend too much of your valuable time trying to assign a fundamental physical significance to H. After you get some experience solving thermo problems, you will become much more comfortable with enthalpy.

3. Feb 6, 2016

### Cole

Fair enough. So then is there a way to conceptually explain ΔG=ΔH-TΔS? Or is that not really possible?

4. Feb 6, 2016

### Staff: Mentor

G is another useful function that comes into play in many types of problems. It too is difficult to assign physical significance to. The more fundamental thermodynamic properties, internal energy U and entropy S, can be assigned physical significance.

Chet