I would do an experiment demonstrating the importance of the values H sub f and H sub v (The energy required to phase change at fusion state or vaporization). To do this, get two materials with vastly different values, and show how much less energy is required to phase change the material with less of the value. It's a pretty simple bunson burner/test tube experiment. Make sure you control the temperatures and heat input adequately, or you may lose points for having invalid results.