What characteristics make igneous rocks useful

Does the energy in a solid increase or decrease when changing to a liquid?

What is the mass of 8 moles of sodium atoms

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