How do intra-molecular hydrogen bonds affect the molecule in its gaseous phase?

Answer 1

In general, the way the hydrogen bonds affect something (like water) in its gaseous phase is that they still want to "hang on a bit" and "connect" the molecules. But they can't because the molecules have too much kinetic energy. Remember that the electrostatic attraction that is the basis for hydrogen bonds didn't just "disappear" when the molecule gained enough energy to escape its liquid associates and become a gas. It's still there and plays a minor role in the behavior of the molecule. There is something else that is important when something like water is a gas in air (because the water molecules have enough energy). A water molecule may form a bond and combine with another molecule briefly, and then break away. In fact, molecules of water may be (will be) forming hydrogen bonds with other moledules and then breaking away all the time. The higher the energy of the system in which the molecules are operating, the less frequently a pair of water molecules will "hook up" and the less time they'll stay together. But the "hook ups" will still happen to a degree. In liquid water, the hydrogen bonds make and break all the time, but the "low energy" in a container of liquid water allows the hydrogen bonds to "call the shots" because the molecules don't have the energy to break away as easily.