Dissolving and solutions

When a solid like sugar is stirred into water and seems to disappear, it has dissolved. The sugar is still there, broken into tiny particles mixed with the water. The mixture is called a solution. The solid that dissolves is soluble; a solid that does not dissolve, like sand or chalk, is insoluble.

Dissolving is reversible and mass is conserved: 100 g of water plus 5 g of salt makes 105 g of salty water. Sugar dissolves faster in hot water than in cold, faster when stirred, and faster when the pieces are smaller, like caster sugar instead of sugar cubes. There is a limit: if you keep adding sugar, eventually no more will dissolve.