Overall Review of Intermolecular Forces

[Kyle Walsh 2J]

Hi! I was rereading my notes on this section and realized that I was somewhat unclear on what I wrote down, especially like the actual applications of intermolecular forces and why they matter in general chemistry. I know the general trends in strength, but what effect does the strength have in the real world? Thanks!

[Zach Richardson 2f]

Well in very large complex proteins for example, hydrogen bonds and Van der Waals interactions play a very important role in tertiary and quaternary structures. The permanent dipole of water is the reason why things dissolve in water and thus why it is necessary for life. A lot of these interactions are present in biology because of the size of molecules that biology deals with.

[Jay Solanki 3A]

Also to add to the above: water's hydrogen bonding allows water molecules to expand when in a crystalline structure (or a solid). this makes the density of this crystalline solid (ice) smaller than water and allows ice to float on water. This allows marine life to prosper well. Just thought I would add in an additional biological application to the aforementioned examples.

[Wil Chai 3D]

More of a specific to chemistry thing, but the strength of IMFs is related to characteristics of substances such as boiling/melting/freezing point, viscosity, heat capacity, and others.

Water, for instance, has a high heat capacity due to H-bonds. When heat is added to water, some energy goes in to breaking those H-bonds, meaning that the temperature does not rise as fast. This helps maintain temp in oceans.

You can also apply this knowledge to the separation of two liquids in a mixture by distillation. This process involves heating up a mixture so the liquid with the weaker IMFs vaporizes, is collected, and then condensed again, giving you two separate liquids. Hope these examples are helpful!

[Katie Nye 2F]

I think the most common usage of this idea would be boiling/freezing/melting points! The stronger the intermolecular force, the higher the boiling/melting points because they require more energy to break the stronger bond.