We can see this electronegativity difference as we begin to cool the gaseous HF and LiF molecules. Nothing happens to HF until the temperature decreases to 19.5°C, at which point the gas molecules are moving so slowly that they can be trapped by forces between molecules and condensed into a liquid.

The individual molecules remain intact in the liquid, with the forces between them being a combination of van der Waals interactions and hydrogen bonds from one H to the F on a neighboring molecule.

At -83°C, molecular motion becomes so slow that these forces freeze the HF molecules into a crystalline solid. Even in the solid, individual HF molecules remain, held together by the forces between molecules.