Exploring thermal
decomposition
Some compounds can break
down into smaller compounds or elements,
usually when they are heated.
This is called ‘decomposition’.

Make sure you wear eye protection and tie
back hair during this practical.

Limewater is an irritant, so avoid contact with
skin.

Boiling tubes can smash if the clamp is closed
too tight

Be careful when handling glass apparatus.
Inform your teacher immediately if there is
any broken glass.
Set up clamp
Using a spatula, add some calcium carbonate to your boiling tube
Place the bung and delivery tube into the boiling tube
Position the boiling tube in the clamp as shown in the diagram
(Make sure the apparatus is clamped high enough to allow you to
remove the test tube of limewater easily)
Pour around 1cm3 limewater into the test tube
Place the test tube into the test tube rack
Fit the delivery tube into the test tube containing limewater
Place a Bunsen burner onto a heat proof mat underneath
the boiling tube as shown in diagram
Check the Bunsen burner tube and set the Bunsen to safety flame