chemistry question?

[Blaze]

i am struggling with a couple questions.
1. Is CH3CH2OH, NH3, and C3H8 non polar or polar?
2. what the heck are IMFs?
if anyone could explain these, id be really grateful
THANKS!!!

[yellowmuskrat]

1. CH3CH2OH has two ends. The CH3CH2 end, which is hydrophobic (water fearing) and the OH end which is hydrophilic (water loving). When a molecule exhibits this "polarization" or the appearance of ends, it is considered polar. So CH3H8 looks like this:

CH3CH2CH3

There is no hydrophilic end, so it is referred to as non polar.

2. Inter molecular forces (IMF's) are pretty straight forward. Outside of true bonding (the sharing of an electron pair) there is what is known as hydrogen bonding. No electrons are being shared in H-bonding. There is attraction how ever because the O atom's valence electrons are attracted to the H atom's proton. This is called an intermolecular force (meaning at the molecular, not atomic level). H-bonding is weak compared to other bonds such as metallic bonding. This is why metal melt at such a high temperature and ice doesn't. It takes far more energy to break metallic bond in metal than it does to break the H-bonds in ice. London dispersion forces are even weaker. You might ask how oil is a liquid at room temp if it has no H-bonding. Well it turns out the since the electrons surrounding the atoms in an oil molecule are in constant random motion, a momentary dipole ("polarization") is formed. The sum of all the oil molecules doing this is attributable to the viscosity and high boiling point of oils.