Outcomes

Note the change of state of Stearic Acid (SA).
List the characteristics of SA in solid and in liquid forms.
Chart the temperature vs. time change solid to liquid.
Chart the temperature vs. time change liquid to solid.
Note the temperature at which liquid goes to solid and solid to a liquid.
Pupils should realise that temperature doesn’t change during a change of state because, for example, the heat input is used to affect the change.
Pupils could be challenged to try and work out what is actually happening to the molecules as the temperature increases. Pupils could act this out.

Specification References

5.9 Understand that a substance can change state from solid to liquid by the process of melting.

Make ice lollies with pupils and discuss how it turns from liquid to solid
Ask students to predict what may happen if we heated solid lollies
Demonstrate how solid Lolly returns to liquid with heat (in microwave)
Note which properties change with the change of state
Have children list physical properties of both substances changing states and which properties remain the same

Have students describe butyl stearate as a liquid and experiment with placing a test tube of this liquid in boiling water and in ice water.
Have ½ student heat and half cool.
Ask what is required to change the state. (Heat must be added or removed).
After students have made the connection between temperature and state, ask them if they think they could find the temperature at which a change of state takes place.
Supply a thermometer and let students find the temperature of the two water baths.
Ask students to place their thermometer in liquid Butyl Stearate and place the test tube in the ice water bath. They must chart the temperature drop until all the liquid solidifies.
Repeat going from solid back to liquid.

Test Tubes, Beakers, Thermometers, Bunsen burners, Butyl SteratePrepared, Squash and 1 popsicle

With help in choosing what to do, present results in a graph Compare results to draw conclusions

Care with hot liquids, pupils should not sit down whilst performing this experiment. Inform pupils what to do in the event of a burn occurring.
The pupils are not to eat the ice lollies.