1. The problem statement, all variables and given/known data When lead is melted at atmospheric pressure, the melting point is 600K, the density decreases from 1.101x104 to 1.065x104 kgm-3. The latent heat is 24.5 kJ kg-1 Estimate the melting point of lead at a pressure of 100 atm. 2. Relevant equations I haven't been able to find any equations for how the melting of a solid varies with pressure. Intuitively I'd say the melting point will go down, but that's really just a guess. 3. The attempt at a solution If the density decreases, the material expands. This means it is doing work on the surroundings, so some energy that goes in does that. I looked at some data from a paper (not what the question wants) that tells me that the melting point of lead goes up as pressure goes up in the range of 800 to 1200 MPa.