112
44.
Classic chemistry experiments
Forming glass
Topic
Making glass, ceramics.
Timing
60 min.
Description
Students make glass and then colour some glass using transition metal oxides.
Apparatus and equipment (per group)
▼ Access to a balance (±0.1 g)
▼ Paper clip
▼ Bunsen burner
▼ Tripod
▼ Pipe clay triangle
▼ Crucible
▼ Heat proof mat
▼ Tongs
▼ Boiling tube and bung.
Chemicals (per group)
Access to:
▼ Copper(II) oxide (Harmful)
▼ Cobalt(II) oxide (May cause sensitisation, harmful)
▼ Manganese(II) oxide
▼ Chromium(III) oxide (Not chromium(VI) oxide)
▼ Lead(II) oxide (Toxic, may cause harm to unborn children and there is a danger of
cumulative effects. Harmful if swallowed.)
▼ Boric acid
▼ Zinc oxide.
Teaching tips
The solids need to be thoroughly mixed. Students can put all three solids in a boiling
tube, use the bung and shake the contents to ensure thorough mixing. Stir the mixture
with an unfolded paper clip. The crucibles need to be dedicated to this experiment.
This practical is suitable for teaching how to use balances and how to handle hot
apparatus. The glass produced is very brittle and difficult to keep. It is better to have a
number of balances available.
Background theory
Very little required. Ceramics and their properties. Practical skills are more important.
Safety
Wear eye protection. Avoid raising lead(II) oxide dust.
Classic chemistry experiments
113
Forming glass
Introduction
The aim of this experiment is first to make some glass and secondly to make some
coloured glass by adding other compounds to the molten glass mixture.
Crucible
Glass melt mixture
Pipe clay triangle
Tripod
Bunsen burner
What to record
Record the colour of the glass produced when a speck of a particular oxide is added.
What to do
1. Weigh 6.5 g of lead(II) oxide, 3.5 g of boric acid and 0.5 g of zinc oxide. Mix
thoroughly in the boiling tube.
2. Pour the mixture into a crucible and place it on a pipe clay triangle.
3. Heat strongly until it becomes molten and runny. Using tongs pour one or two
drops of the molten glass onto your heatproof mat.
4. Allow the beads to cool for 5 min and then examine them.
5. Using an unfolded paper clip pick up a tiny amount of transition metal oxide and
drop it into the remaining molten mixture. Stir in the powder using the paper clip.
Do not add too much powder or you will produce a very dark piece of glass.
Safety
Wear eye protection. Care must be taken with the lead(II) oxide, as it is toxic. Avoid
raising the dust. Some of the other chemicals are harmful.