Final answer:
Compounds with hydrogen bonds have the strongest intermolecular forces in the experiment, affecting vapor pressures and boiling points significantly.
Step-by-step explanation:
Out of all compounds, compounds with hydrogen bonds have the strongest intermolecular forces (IMFs) in our experiment. Hydrogen bonds, while significantly weaker than covalent bonds, greatly affect a compound's physical properties due to their relatively strong intermolecular attraction. Compounds exhibiting hydrogen bonding, such as water, have low vapor pressures because their strong IMFs are harder for the molecules to overcome. As molecular size increases, dispersion forces also increase, leading to even lower vapor pressures as the trend Pmethanol > Pethanol > Ppropanol > Pbutanol shows.
In terms of strength of IMFs, the hierarchy is ionic bonding > hydrogen bonding > dipole-dipole interactions > dispersion forces. The stronger the IMFs, the lower the vapor pressure and, consequently, the higher the boiling point of the substance.