Describe the motions of particles in three common states of matter

According to each substances heat of fusion, which of the items below requires more heat to be added per gram of substance to go from solid to liquid? silver sulfur water lead

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms

Chemistry worksheet - i am not sure what they are asking for exactly?