The rate of dissolving usually depend upon the stirring, temperature of solvent and particle size of solute.
The solute is more rapidly dissolve if we stir it in the solvent and when the temperature of solvent is high because the solute particles gain more energy of movement. The rate of dissolving is also increase when the particle size of solute is smaller. It can also be understand by taking the example of sugar.
Example:
Consider the single particle of sugar and a cube of sugar that consist of many sugar particles together, put these two in a separate glass of water. We will observe that the single particles dissolve rapidly as compare to the cube of sugar. The reason is that single particles have large surface area thus create greater interaction with solvent and dissolve rapidly.
