Hot water dissolves more

The idea

For most substances solubility increases with temperature, so a solution saturated at one temperature behaves as an unsaturated solution when its temperature is raised.

Baking soda

You dissolve baking soda in water at 20 °C, 50 °C and 70 °C.

In which water does the most baking soda dissolve?

• The water at 70 °C
• The water at 20 °C
• The same in all

Compare temperatures

Open each tab.

Warmer, more

For most substances the solubility increases as the temperature increases. A solution that is saturated at one temperature behaves as an unsaturated solution if the temperature is increased.

For most substances, solubility increases with temperature. A saturated solution behaves as unsaturated when heated.

Notes

Heating raises the solubility of most solids.

Check yourself

For most substances, solubility …

Which water dissolves the most baking soda?

A saturated solution is heated. It now behaves as …

Undissolved solute at the bottom of a saturated solution. After heating, more of it …

• increases with an increase in temperature — correct. Yes!
• decreases with an increase in temperature. For most solid solutes it increases.
• never changes. It changes with temperature.
• Water at 50 °C. Water at 70 °C dissolves more than water at 50 °C.
• Water at 70 °C — correct. Yes!
• Water at 20 °C. Water at 20 °C dissolves the least.
• a saturated solution still. More solute can now dissolve.
• a pure substance. It behaves as an unsaturated solution.
• an unsaturated solution — correct. Yes!
• can dissolve — correct. Yes!
• cannot dissolve. On heating, the solubility rises, so more can dissolve.
• turns into solvent. More solute can dissolve after heating.