Dissolving occurs when solid materials are broken down into molecules in a liquid. The gaps between the molecules of one material are then filled by the molecules of the other material. Solute (a solid that dissolves in a solvent) particles are sometimes bigger than the particles of the solvent (a liquid that will dissolve a solute). An example is sugar particles in water.
The speed at which materials will dissolve can vary depending on:
- size: large granules of a solute dissolve more slowly than smaller particles because the solvent acts on the surface area of the solute. In cooking, fine table salt dissolves much quicker than sea salt.
- temperature: a warm solvent contains more energy than a cold solvent (the molecules are therefore moving more slowly). This means that in a warm solvent the granules will be broken down much more quickly. When you have a drink, sugar dissolves more quickly in a hot drink than in a cool drink.
- agitation: if the solute and solvent are agitated by stirring, the speed of dissolving increases. Again, this is due to an increased energy level. When you add sugar to a hot drink, stirring aids the dissolving process. If it is not stirred, some of the sugar often remains at the bottom of the cup.