Liquid and Solid Formation

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Brandon Mo 4K
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Joined: Fri Sep 28, 2018 12:15 am

Liquid and Solid Formation

Postby Brandon Mo 4K » Fri Nov 09, 2018 12:46 am

How does the strength of dispersion forces explain whether a molecule is liquid or solid?

Also, during the lecture on 11/7/18, why does CH4 boil at a lower temperature than CCl4?

Posts: 78
Joined: Fri Sep 28, 2018 12:17 am

Re: Liquid and Solid Formation

Postby ChathuriGunasekera1D » Fri Nov 09, 2018 1:08 am

The stronger the dispersion forces, the stronger the force between the molecules. The stronger the intermolecular forces (IMFs) are, the more solid the compound becomes (except for H20, which has stronger IMF as a liquid vs. solid, which explains why water is denser than ice).

IMFs will form between H and H for CH4 molecules, and between Cl and Cl for CCl4 molecules. Dispersion forces are stronger in Cl - Cl bonds because Cl has more electrons that are farther from the nucleus, so it's more polarizable (easy to push electrons around), and therefore more likely to form stronger dispersion forces. If the IMFs are stronger, then they require more energy to break, which is why the BP of CCl4 is higher than CH4.

Aaron Ang 4H
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Joined: Fri Sep 28, 2018 12:28 am

Re: Liquid and Solid Formation

Postby Aaron Ang 4H » Fri Nov 09, 2018 1:09 am

Molecules in a liquid form are more spread out than molecules in a solid form therefore the intermolecular forces in between them are weaker in the liquid form as opposed to the solid form. To answer your second question, CCl4 has a higher boiling point than CH4 because it has more electrons and therefore experiences stronger dispersion forces therefore they require more energy to break their bonds than CH4 which explains why CH4 boils at a lower temp and CCL4 boils at a higher temp.

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