Why does sugar stop dissolving in tea?
At a given temperature, a fixed amount of water can hold only so much dissolved sugar at equilibrium. Once the solution is saturated, extra sugar can remain as crystals.
- The scientific idea
- Solubility
- Fields of science
- Chemistry
How it works
Sugar that vanishes into tea has not ceased to exist. Its molecules have dispersed among the water molecules. Add enough sugar, however, and some can remain as crystals even after the mixture has reached equilibrium: the solution is saturated.
Look closer
The limit changes with temperature. Hot water can dissolve substantially more table sugar than the same amount of cold water, while table salt shows a much smaller change. That difference matters: there is no rule saying every solid becomes dramatically more soluble when heated. Dissolving speed and solubility also answer different questions. One concerns how quickly a mixture changes; the other concerns how much can remain dissolved at equilibrium.