Which type of intermolecular forces need to be overcome to convert each of the following from a liquid to a gas? 

(a) CH₄, 

(b) CH₃F, 

(c) CH₃OH 

Strategy Dispersion forces will exist for any substance but will be the most important forces only in the absence of stronger dipole–dipole or hydrogen bonding interactions. To see if those stronger forces are possible, we need to look at the structure of each compound. So we might start by using Lewis structures to establish the molecular geometries. In this case, we are dealing with methane, whose structure we know well, and two closely related compounds.