How come not all substances are water-soluble?
Polarity determines if a substance is water-soluble. A polair substance is a substance that has two kinds of ‘poles’, as in a magnet. When another substance is also polair the poles of the substances attract each other and as a result the substances mix. A substance then dissolves in water. Substances that contain no ‘poles’ are called apolair substances. Oil for instance is an apolair substance, which is why oil does not dissolve in water. In fact it floats on water, just like ice, due to its smaller density.
