How does the polarity of a substance affect its solubility in water?
Water is polar and polar compounds like to dissolve other polar compounds. So the more polar a compound, the more soluble it is in water.
There are 2 main inter-molecular forces (Forces that pull molecules towards other molecules) that are at work in any mobile substance.
- London/Dispersion Forces - These forces are present in any substance and increase directly with the size of the molecules discussed (
#C_4H_10 > CH_4#)
- Dipole-Dipole Interactions - These forces are only present in molecules that have a Positive and Negative pole (Polar). The Positive pole of one molecule is attracted to the negative pole of another molecule, thus holding these molecules together similar to a bag of magnets.
The level of polarity is determined by examining the electronegativity differences in the molecule at large. If these differences result in an overall pulling of electrons to one side or another then the molecule is polar.