Intermolecular forces determine whether a substance will dissolve in another. For dissolution to occur, the molecular bonds in both the solute and solvent must be broken as the solute molecules are inserted into the solvent. This requires energy. If the bonds between solute molecules or solvent molecules are too strong and there is not enough energy provided, dissolution will not take place. For example, sugar dissolves in water as the energy released by bonds forming between sugar and water molecules is enough to overcome the bonds within sugar molecules and water molecules. Similarly, ionic compounds like salt dissolve when the energy released by interaction with the solvent is greater than that needed to break the ionic bonds between its ions.

1. Why do things dissolve?
Why sugar dissolves in water?
Why do things dissolve
Probably everyone wondered at least once, why does sugar dissolve in tea. Here we will not focus on sugar as such
but basically on a problem - why some things dissolve and some do not?
Intermolecular forces
In process of dissolving, molecules of the solute are inserted into a solvent and surrounded by its molecules. In order
for the process to tak place, molecular bonds between molecules of solute (ie. sugar) have to be broken and
molecular bonds of the solvent also have to be disrupted. Both of these require energy.
Example of sugar
When sugar dissolves in water, new bonds between sugar and water are created. During this process energy is given
off. The amount of this energy is sufficient to brake bonds between molecules of sugar and between molecules of
water. This example is relevant to any solute and solvent. If the bonds between solvent or solute are to strong and
there is not enough energy provided while dissolving to brake them, the solute will not dissolve.
Example of salt (Ionic compounds)
The same energy rule can be applied to salts. They are build of positive and negative ions which are bound together
by the force of attraction of their opposite charges. If energy needed to brake their ionic bounds is lower then the
energy given off by an interaction of the ions with solvent (ie. water), the salds will dissociate and iteract with solvent
and thus dissolve.