Exothermic Reactions

Exothermic reactions

When quicklime is mixed with water an exothermic reaction takes place. A temperature sensor can collect information about the heat generated over time. Other things being equal, this reaction might be used in a ski boot heating pack. The proportions of the mixture are important. If icing sugar is added to the lime mixture the rate of heat generation changes. You can investigate the result of adding different amounts of sugar (or water) to the lime - seeing which will produce the most heat for the longest time. You can then determine which mixture is best.

What you need

exother.jpg (13772 bytes) Beakers, insulation for the beaker, test tube, balance to weigh solids, icing sugar, quicklime, plastic gloves, interface and temperature sensor.

Setting up

Connect a temperature sensor to the interface.
Place the measured, solid ingredients in a beaker. Put the temperature probe in a test-tube with a measured volume of water.
Start your sensing software - it should recognise the sensors you attach automatically.
Set up your software to record for 15 minutes. Add water to the solids and stir.
Repeat the experiment using different mixtures of lime and icing sugar.

Questions

How does the graph tell you that the mixture is getting hotter?
At what point in the reaction does the mixture get hot fastest?
How long does the heating effect last for?
What might the area under each graph be a measure of?
How can you decide which mixture is the best?
Save your data on disc and print the graph.

Teacher question

What is the best way of comparing these reactions? What is the area under the graph a measure of? How appropriate and useful is this measurement? Click here to respond.

This activity was adapted by Roger Frost from The IT in Science book of Data logging and Control. This page is � IT in Science. It may be reproduced only for use within your school.