What is Aluminum's ion charge?

Why are pipes bursting in the in extremely cold weather?

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

How might this scientific phenomena be explained? a paper clip floats on water.