4.3.1 Describe the types of intermolecular forces (attractions between molecules that have temporary dipoles, permanent dipoles, or hydrogen bonding) and explain how they arise from the structural features of molecules
- for a molecule to be polar, there must be an overall unequal distribution of electrons in the molecule
- if a molecule contains only pure covalent bonds, the molecule will be non polar
- if a molecule contains polar covalent bonds, whether or not the molecule is polar depends on its 3D shape
- dipole-dipole interactions is when the polar and non-polar areas on different molecules attract each other
- hydrogen bonding is an extreme case of dipole-dipole interaction when the F, O, N lone pairs on a molecule attracts a hydrogen bonded to a F, O, or N on a different molecule
- for nonpolar molecular aggregates, there are no dipoles to interact
- however, there are temporary electron imbalances created by random electron movement with nonpolar molecules
- the temporary imbalances can interact with each other and create temporary induced dipoles in other molecules
- the resulting attractions are Van der Waal's/London forces
4.3.2 Describe and explain how intermolecular forces affect the boiling points of substances
- the stronger the intermolecular force, the harder it is to break the bonds required for the substance to reach boiling point and undergo phase change
- thus, hydrogen bonded molecules will have the higher boiling points than regular dipole-dipole molecules, with London forces molecules having the lowest boiling point out of the 3 types of interactions