Liquid State Bonding

Three intermolecular forces to consider

• London Disperson Forces
• Dipole-dipole
• Hydrogen bonding

The strength of the bonding force is indicated by the boiling point of a substance.

Remember that boiling separates one molecule from another. Boiling DOES NOT break molecules apart - that is, DOES NOT separate atoms from each other.

A few useful links:

(1) London & dipole-Dipole

http://www.chemguide.co.uk/atoms/bonding/vdw.html#top

(2) H-bonding

http://www.chemguide.co.uk/atoms/bonding/hbond.html#top

(3) All 3 intermolecular forces

http://www.science.uwaterloo.ca/~cchieh/cact/c123/intermol.html

In order of increasing strength:

London (LDF) - weakest

• dependent upon the number of electrons
• greater number of electrons, greater London forces
• shape plays a role too, straight chain hydrocarbons tend to have higher bpt than branched chains of similar atom count

Dipole-Dipole (DDF)

• force of polar molecules
• polar molecules rely on shape of molecule
• polar molecules also have LD forces

H-bonding - strongest

• molecule must have H-N, H-O and/or H-F bond
• molecules will also have DDF and LDF

A typical liquid state bonding question would ask you to explain the difference in boiling points of various substances. Given a chemical formula, you need to be able to identify the type of liquid state bonding force involved with each molecule.

[The end of a much delayed post. Since water has all three bonding forces present, the chosen font colour for this little section is blue. Ready for a joke? Question: What did the sink say to the water faucet? Answer: You're a real drip. :<]