Why would a molecule such as methane not dissolve well into water?

1 Answer
anor277 · shr
Nov 5, 2016

Well, methane is a non-polar molecule. These nonpolar molecules don't dissolve so well in water. You may have heard #"like dissolves like"#, since water is polar, it naturally tends to dissolve with other polar molecules.

Explanation:

Well, methane is a non-polar molecule that contains relatively non-polar #C-H# bonds. The #C-H# bond has negligible dipole moment, and even if it did have some polarity, the tetrahedral shape of the molecule would give no net dipole. Compare the solubility of #"CCl"_4# in water which is also poor.

As chemists, as physical scientists, however, we should always seek out the data to inform our argument. This site quotes a solubility of #0.04*g*kg^-1"(of water)"#, which is comparable to the solubility of the dinitrogen molecule under equivalent conditions.

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