ChemixaLEARN CHEMISTRY

Sugar solubility versus temperature

Objective: compare how much sugar dissolves in cold versus warm water and explain the difference using solubility and kinetic energy. You will add sugar spoonful by spoonful, find the saturation point for each temperature, and record your results.

Safety:

Use warm tap water, not boiling water, to avoid burns. An adult should handle any water hotter than comfortable tap temperature. Adult supervision is required for minors. Clean up sticky spills promptly.

Materials

  • Sugar
  • Two identical clear glasses
  • Cold water
  • Warm water (not hot)
  • Teaspoons
  • Stirring sticks
  • Thermometer (optional)

Procedure

1

Prepare two water samples

Fill two identical glasses with equal amounts of water: one cold from the tap, one warm from the tap.

2

Add the first spoonful

Add one teaspoon of sugar to each glass and stir until it fully disappears.

3

Add sugar spoon by spoon

Keep adding sugar one teaspoon at a time, stirring until each spoonful dissolves before adding the next.

4

Find the saturation point

Stop when a spoonful refuses to dissolve after a full minute of stirring; undissolved crystals should remain visible.

5

Compare the totals

Count the total spoonfuls each glass accepted and compare the two totals.

What to observe

  • Sugar disappears quickly at first in both glasses.

  • The warm water keeps accepting sugar long after the cold water stops.

  • Undissolved sugar piles at the bottom of the cold glass first.

  • Stirring speeds up dissolving but does not change the final amount that dissolves.

Why it happens

Solubility is the maximum amount of solute that dissolves in a given amount of solvent at a given temperature. For most solid solutes like sugar, solubility increases with temperature because the faster-moving water molecules can pull more sugar molecules away from the crystals and keep them dispersed. When no more sugar dissolves and crystals sit on the bottom, the solution is saturated. Heating increases kinetic energy, which both speeds up dissolving and raises the saturation point, so warm water holds noticeably more sugar than cold water before saturating.

Try variations

  • Repeat with salt and compare its temperature sensitivity to sugar's.

  • Chill one glass in the fridge and test again at a lower temperature.

  • Time how long one spoonful takes to dissolve in each glass.