THE EFFECT OF TEMPERATURE ON THE RATE OF DISSOLVING
The purpose of this demonstration is to show the effect of temperature on the rate of dissolving of a solid in a liquid.
This demonstration is appropriate for a middle school or general chemistry course. The rate at which Kool-Aid dissolves in water at three different temperatures is observed.
*See Modifications / Substitutions
Clear plastic cups may be substituted for beakers.
- tap water--hot, room
temperature, and cold
- Kool-Aid--grape or cherry
- chemical scoop or spoon
Pour solutions down drain.
Increasing the temperature increases
the rate of dissolving because, at higher temperatures, the solvent
molecules are moving more rapidly and therefore come into contact
with and solvate the solute molecules more rapidly.
This demonstration could be done on
an overhead projector. Undissolved material would appear opaque
and the depth of color of the solution could be used to observe
rate of dissolving.
- Label beakers hot, room temperature, and cold.
- Fill each beaker about three-fourths full of water of the
appropriate temperature. The volumes should be the same.
- Add about one-eighth to one-fourth teaspoon of Kool-Aid to
each beaker. The amounts should be the same.
- Observe the rates at which the Kool-Aid dissolves.
Submitted by Patti Ruff, Bill Vitori, Irene Walsh, Doug Wilbur, and Joe Don Wilkins
Woodrow Wilson Leadership Program in Chemistry
The Woodrow Wilson National Fellowship Foundation
CN 5281, Princeton NJ 08543-5281