Science required practicals
How do you do the thermal insulation required practical?
You put hot water in a beaker, surround it with an insulating material, and record the temperature every few minutes as it cools. Repeat with different materials, then with different thicknesses of one material, keeping the volume of water and the starting temperature the same. The best insulator shows the smallest temperature drop in the same time. This practical is for separate Physics only, not Combined Science.
Last updated 23 September 2026 · Written and fact-checked by the GCSEwiz team
What does the thermal insulation practical investigate?
It tests how well different materials slow down the transfer of energy from hot water to the surroundings, and how the thickness of a material changes that. A good insulator has a low thermal conductivity, so energy passes through it slowly and the water stays warm for longer.
It is a required practical on AQA GCSE Physics only. If you are taking Combined Science: Trilogy, it is not on your list, and you do not need it.
What equipment do you need?
The usual set-up is a small beaker of hot water standing inside a larger one, with the material you are testing packed into the gap between them.
- A small beaker and a larger beaker it fits inside
- A kettle for hot water, and a measuring cylinder
- A thermometer or temperature probe
- A stopwatch
- A card lid with a hole for the thermometer
- Insulating materials to test, such as bubble wrap, cotton wool, newspaper and felt
- Elastic bands or tape, to hold wrapped layers in place for the thickness test
What is the method?
You run the same cooling test several times and change only the insulation. The first part compares materials. The second compares thicknesses of one material.
- Stand the small beaker inside the large one and pack the first material into the gap all the way round.
- Pour the same volume of hot water into the small beaker every time.
- Put the lid on and push the thermometer through the hole into the water.
- When the temperature has fallen to a chosen starting value, such as 80 °C, start the stopwatch.
- Record the temperature every 2 minutes for 20 minutes.
- Empty the beaker and repeat with each of the other materials. Do one run with nothing in the gap, to compare against.
- For the thickness test, take the small beaker out of the large one and wrap it in different numbers of layers of one material, such as 2, 4, 6 and 8 sheets of newspaper, and run the same test for each.
What are the variables?
In the first part you change the material, and in the second you change its thickness. Either way, you measure how far the temperature of the water falls in a set time.
| Variable | In this practical |
|---|---|
| Independent variable | The insulating material, or in the second part its thickness (the number of layers) |
| Dependent variable | The temperature of the water over time, or how far it falls in a set time |
| Control variable | The volume of hot water |
| Control variable | The starting temperature of the water |
| Control variable | The beakers and the lid, the same for every run |
How do you work out and present the results?
There is no equation to use here. You compare how far the temperature fell in the same time, so for each run work out the drop: the starting temperature minus the temperature at the end.
Example: every run starts at 80 °C and is read again after 20 minutes. With nothing in the gap, the water falls to 56 °C, a drop of 24 °C. With material A it falls to 62 °C (a drop of 18 °C), and with material B to 67 °C (a drop of 13 °C). Material B insulated best, because its water cooled the least in the same time.
Plot temperature (y-axis) against time (x-axis) for every run on the same axes, with a smooth curve for each. The curve that falls most slowly belongs to the best insulator. Every curve is steepest at the start, because hot water transfers energy to the surroundings faster when it is much hotter than the room.
For the thickness test, plot the temperature drop after your set time against the number of layers. The drop usually gets smaller as you add layers, with each extra layer making less difference than the one before.
How do you make it accurate and safe?
Start timing when the water reaches your set temperature, not the moment you pour. Water just off the boil cools fastest, so a run that starts hotter would show a bigger drop whatever it is wrapped in. Use the lid on every run, including the one with no insulation, so the energy escaping from the top is the same each time. Pack each material evenly and read the thermometer at eye level. A temperature probe with a data logger helps, because it takes each reading at exactly the right moment.
On safety: water from a kettle can scald. Stand the beaker on the bench before you pour, never pour into a beaker you are holding, and mop up spills straight away. Leave the water to cool before you empty the beakers.
What do exam questions ask about it?
Questions often give you a table or a set of cooling curves and ask which material is the best insulator, and how you can tell. Others ask for control variables, or why every run must start at the same temperature. Some link the results to buildings: thicker walls, and walls made of materials with a low thermal conductivity, slow down the rate at which a house cools.
Here is one we wrote in the exam style: "Two students test the same material. One starts timing when the water is at 90 °C and the other at 70 °C. Explain why their results cannot be compared fairly. (2 marks)" A good answer says the hotter water cools faster at first, so its drop would be bigger even with identical insulation.
Common mistakes
- Starting the timer as soon as you pour. The water cools fastest in the first minute, so start at a fixed temperature instead.
- Changing the volume of water between runs. A smaller volume cools faster, which hides the effect of the material.
- Joining the points with straight lines. Cooling curves bend, so draw a smooth curve through them.
- Leaving the lid off one run. More energy escapes from the top, and that is not what you are testing.