when liquid evaporates we know that it's going from a liquid to a gas therefore going from an ordered state to a more chaotic disordered state meaning the entropy which is the measure of order, goes up. Since this is a spontaneous reaction at high temperatures and non spontaneous at low temperatures and free energy is negative for spontaneous then we can say at high temperatures free energy is negative and at high temps and positive at low temps. Also since evaporation requires energy to evaporate the enthalpy is positive.
