Development of the Modern Freezer. Bacteria are usually the cause of food decay, but they can't grow as well or at all in freezing temperatures, which are at 32 degrees Fahrenheit (0 degrees Celsius) or lower.
HF- polar molecule: dipole-dipole forces. There are also dispersion forces and H bond between HF. BF3- nonpolar: dispersion forces. Ar- Dispersion forces between Ar atoms.
The answer is because HF molecules are so very polar (due to the high electronegativity of the F atom, HF molecules have many strong Hydrogen bonds --> H----F- - -H----F- - -H----F- - -H. Where H----F is the covalent bond and H- - -F is the Hydrogen bond.