The substance that would most likely need to cool to the lowest temperature before it condenses is ethane, a non-polar covalent compound.
Ethane in liquid form has very weak attractive forces binding the molecules together.
To form and change state, all the molecules must be brought very close together under very high pressure and low temperature. Else, they will not attract one another.
Ionic crystal lattice forces as seen in KBr are strong attractive forces. As a substance such as KBr begins to condense, they begin to attract one another with a very strong force even before they cool to their least temperature.
Ammonia has strong intermolecular hydrogen bonds in its structure which binds them together. The attraction is great between the hydrogen of one molecule and the nitrogen of another.
