Helium forms a solid at low temperatures and high pressures. To maintain the order present in a solid, each atom must remain at its assigned position. Suppose that this restricts the uncertainty in the position to 0.19 nm.
(a) Find the uncertainty in momentum of the helium atom. Use deltax * deltapx >= h/2 for the uncertainty principle.
(b) Find the uncertainty in the kinetic energy of the helium atom. At low pressures, the bonds between helium atoms are not very strong. They cannot hold together atoms with this amount of kinetic energy. The zero point motion produced by the connement of the helium atom is great enough to break the bonds. For this reason helium does not form a solid at low pressures, even at absolute zero temperature. Helium forms a solid only if high pressure on its surface assists the bonds in holding together the atoms.