Glass and ceramics both resist heat and chemicals, but each use depends on a different property. This lesson shows how to pick the right one from what the job needs.
This lesson sits in SPM Chemistry manufactured materials. It follows explaining alloy properties using structure.
Which glass is used for which job?
Start from the property the job needs, then pick the glass. Each type is silica with a different addition.
| Glass | Main substances | Key property | Use |
|---|---|---|---|
| Fused glass | Silica only | Very high melting point, resists heat shock | Optical fibres, lenses, lab tubes |
| Soda-lime glass | Silica, sodium carbonate, calcium oxide | Cheap, easy to shape, softens at lower temperature | Windows, bottles, light bulbs |
| Borosilicate glass | Silica, boron oxide | Low thermal expansion, resists chemicals | Oven dishes, lab beakers, flasks |
| Lead crystal glass | Silica, lead(II) oxide | High refractive index, bright sparkle, heavy | Decorative glasses, chandeliers |
What are ceramics and where are they used?
Ceramics are made by shaping clay-based material and firing it at high temperature. The result is hard, brittle, heat resistant and a poor conductor of electricity.
The bonds in a ceramic are strong and hold every atom in place. No layers slide, so a ceramic resists scratching and heat but shatters under a sharp knock.
- Bricks and roof tiles: hard and weather resistant.
- Crockery and sinks: chemically inert and easy to clean.
- Electrical insulators on power lines: do not conduct electricity.
- Engine parts and furnace linings: survive very high temperatures.
Worked example: choosing a material for oven cookware
Question. A company makes a dish that goes straight from the freezer into a hot oven. Choose the glass it should use and explain your choice. [3 marks]
List answer (1 mark). “Borosilicate glass is used for cookware.”
Reasoned answer (3 marks).
- The dish is heated and cooled quickly, so the glass needs a low thermal expansion.
- Borosilicate glass contains boron oxide, which gives it this property, so it does not crack.
- Soda-lime glass expands more when heated, so it could crack. That is why it is used for bottles, not oven dishes.
The reasoned answer names the property, links it to the composition, and rejects the obvious alternative in one line. That last step is what lifts a 2-mark answer to 3 marks.
A fast way to rebuild the table in an exam
Ask two questions of any use. Does it need to survive heat shock, or does it need to be cheap and moulded easily? Does it need to bend light, or be chemically clean?
Heat shock points to fused or borosilicate glass. Cheap and easy to mould points to soda-lime glass. Bending light points to lead crystal. Note which of these you mix up in your mistake log.
Check yourself
A factory needs a material to line a furnace that reaches a very high temperature. State whether glass or ceramic suits better, and give two properties that justify it.
Answer
A ceramic suits better. It has a very high melting point and stays hard at high temperature, so the lining does not melt or soften.
It is also a poor conductor of heat and electricity, which reduces heat loss through the furnace wall. Ordinary soda-lime glass would soften long before the furnace reaches working temperature.
What to study next
The next lesson, relating polymer and composite properties to uses, adds materials that combine two substances. Then use the practice set to test the property-to-use link.
If you want a teacher to drill this with you, see online one-to-one Chemistry tuition.