Full Up! Saturation

Why it matters

Keep adding sugar to a glass of water and stirring. At some point the sugar just sits at the bottom and will not disappear. The water is full up!

Predict first

In which glass will the MOST sugar dissolve?

Hot water can dissolve much more sugar than cold water, because solubility increases with temperature. Stirring the hot water helps the sugar dissolve quickly too.

• Cold water that you do not stir
• Hot water that you stir well — correct
• Cold water that you stir hard
• Ice-cold water in the freezer

What you do

Put the glasses in order, from the one that dissolves the MOST sugar to the one that dissolves the LEAST.

Check yourself

What happens to the amount of sugar water can dissolve as you heat the water up?

For most solids, solubility increases with temperature. Hot water can hold far more dissolved sugar than cold water.

A solution that has dissolved as much sugar as it possibly can at that temperature is called:

A saturated solution holds the maximum amount of solute possible at that temperature. Any extra sugar just settles at the bottom.

You stir a glass of sugar water hard with a spoon. What does the stirring actually do?

Stirring only makes sugar dissolve more quickly. The greatest amount that can dissolve is decided by the temperature, not by stirring.

• It increases, because solubility increases with temperature — correct
• It decreases, because heat pushes sugar out
• It stays exactly the same
• The sugar catches fire
• A saturated solution — correct
• An unsaturated solution
• A dilute solution
• A frozen solution
• It makes the sugar dissolve faster, but does not raise the maximum amount that can dissolve — correct
• It lets the water dissolve much more sugar than before
• It turns the sugar into salt
• It stops the sugar dissolving completely