how can you tell if a molecule is polar? also, what is the difference between dipole and dipole-dipole molecules?
A polar molecule which has a net dipole moment due to its having unsymmetrical polar bonds.
There are two factors that go into determining if a molecule is polar or non polar
The polarity of the individual bonds in the molecule.
The shape or geometry of the molecule.
Greater the electronegativity difference, the more ionic the bond is. Bonds that are partly ionic are called polar covalent bonds.
A bond between 2 nonmetal atoms with different electronegativities and have unequal sharing of the bonding electron pair
The bond where the electron pair is displaced toward the more electronegative atom obtains a partial-negative charge while the less electronegative atom has a partial-positive charge
Dipole molecules in which different atoms are bonded by a covalent bond, which can have different electron affinity, then the the atom with greater electron affinity will attract the electron pairs more strongly.
Dipole-dipole molecule have Dipole-dipole force which are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule.
Dipole-Dipole forces are the attractive forces between molecules that have a permanent net polarity. That is, between polar molecules.