Free energy under constant pressure.
A. Changes in Gibbs free energy (delta G), enthalpy (delta H, loosely heat change), entropy (delta S, loosely disorder).
At constant pressure, a spontaneous reaction (i. e. anything that happens under these conditions) will have a negative Gibbs free energy change.
B. Delta G and hydrophobic interactions.
Hydrophobic interactions are driven by a positive change in entropy for separation of the aqueous and hydrophobic phases. This is due to increased disorder in water molecules when they are not in contact with the hydrophobic compounds.