{"id":1123,"date":"2018-02-23T10:39:23","date_gmt":"2018-02-23T18:39:23","guid":{"rendered":"https:\/\/magoosh.com\/mcat\/?p=1123"},"modified":"2019-05-06T08:55:10","modified_gmt":"2019-05-06T15:55:10","slug":"mcat-review-topic-intermolecular-forces","status":"publish","type":"post","link":"https:\/\/magoosh.com\/mcat\/mcat-review-topic-intermolecular-forces\/","title":{"rendered":"MCAT Review Topic: Intermolecular Forces"},"content":{"rendered":"

\"MCAT<\/p>\n

The MCAT will test you on intermolecular forces. Take note, this is an important section on the MCAT because it can be used to predict trends in things like boiling and melting points. So make sure that you have this down!<\/p>\n

If you\u2019re ready to start studying, check out our free video lesson<\/a> on MCAT Intermolecular Forces, and keep reading for a quick review of intermolecular forces.<\/p>\n

\"\"<\/a><\/p>\n

MCAT Intermolecular Forces Review<\/h2>\n

Let\u2019s take a look at three kinds of intermolecular forces:<\/p>\n

1. London Dispersion Forces<\/h3>\n

London dispersion forces involve what are called temporarily induced dipoles.<\/strong><\/p>\n

A dipole can be temporarily induced when we have a long, straight alcane with all the electrons on one side of the molecule, which will repel the electrons of the next molecule.<\/p>\n

By inducing a dipole, we’ve made this a quasi-polar compound. This will slightly increase the boiling point.<\/p>\n

London dispersion forces are size dependent<\/strong>. The longer this chain is (i.e. the more electrons that exist in the compound), the easier it is to polarize the compound, making London dispersion forces stronger. <\/p>\n

2. Dipole-Dipole Interactions<\/h3>\n

Dipole-dipole interactions occur between polar molecules. <\/strong><\/p>\n

An example of a polar molecule would be CH3Cl, or chloromethane. Chloromethane is a carbon with three hydrogens and a chlorine attached to it. <\/p>\n

The carbon-hydrogen bonds are essentially non-polar, but the carbon-chlorine bond is polar. This results in a slightly positive charge on the carbon and a slightly negative charge on the chlorine, because it is more electronegative and will suck up those electrons to hold on to it. <\/p>\n

This results in a much stronger attraction between the molecules in their solid and the liquid forms than in their vapor form<\/strong>. In the vapor, there is still this attraction if they come close to each other, but since vapor molecules tend to be so far apart, this force isn’t as strong. The result of this dipole-dipole interaction though, is that molecules want stay as the liquid for as long as possible, because there are intermolecular forces holding them together. <\/p>\n

3. Hydrogen Bonding<\/h3>\n

Hydrogen bonding occurs when hydrogen is bonded to: <\/p>\n