What does IMF do?
IMF, or Intermolecular forces are the forces that hold two covalent molecules to one another.
If we talk about water, the forces that attract one water molecule to another nearby water molecule are intermolecular forces.
If a compound experiences strong intermolecular forces such as hydrogen bonding, it will have a higher melting and boiling point. This is because hydrogen bonding helps to stick the molecules together, making it harder to pull them apart. Because energy is required to make this kind of change take place, more energy in the form of heat will be needed to make hydrogen-bonded molecules melt.
Another thing that intermolecular forces can do is to explain the saying "like dissolves like". It means that molecules with similar polarities tend to dissolve one another. If you know how to find the intermolecular forces a molecule experiences, you can figure out whether one thing will dissolve another based on their polarities.