Interactive practical

Thermal insulation

Wrap a beaker of hot water in different materials and different thicknesses of newspaper, and compare the temperature drop over ten minutes.

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GCSE Physics

Comparing thermal insulation

AQA 8463 — matched to your course.

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Practical focus

Compare how different insulating materials or material thicknesses affect the rate of cooling.

Practical method

Aim

Compare how well different materials insulate a beaker of hot water by measuring how quickly it cools.

Variables

Independent variable: the insulating material (or its thickness)
Dependent variable: temperature drop in a fixed time (cooling rate)
Control variables: volume and starting temperature of water; size and type of beaker; thickness of each material; lid and room conditions.

Apparatus

Identical beakers
Kettle
Measuring cylinder
Thermometers or temperature probes
Stopwatch
Insulating materials (cotton wool, bubble wrap, newspaper)
Card lids

Method

Wrap each beaker in a different material of the same thickness; leave one unwrapped as a control.
Pour 200 cm³ of hot water at 80 °C into each beaker and fit a card lid with a hole for the thermometer.
Record the temperature every 2 minutes for 10 minutes.
Calculate the temperature drop for each material over the same time.
Repeat and plot temperature against time for each material on the same axes.

Sample results

Temperature of 200 cm³ of water starting at 80.0 °C.

Material	Temperature after 10 min / °C	Drop / °C	Mean cooling rate / °C per min
None	61.0	19.0	1.90
Newspaper	67.0	13.0	1.30
Cotton wool	70.5	9.5	0.95
Bubble wrap	72.0	8.0	0.80

Analysis

Bubble wrap gave the smallest temperature drop (8.0 °C in 10 minutes, 0.80 °C per minute), so it was the best insulator under these conditions. Trapped air is a poor conductor and stops convection currents, which reduces the rate of energy transfer.

Errors and improvements

Problem	Effect	Improvement
Starting temperatures not equal	Unfair comparison: hotter water cools faster	Start timing when each beaker reaches 80 °C
Different thicknesses	Thickness, not material, may cause the difference	Use the same number of layers
Only one run	Random variation not revealed	Repeat and calculate means

Risk assessment

Hazard	Risk	Control measure
Hot water	Scalds	Carry beakers on a tray; do not overfill
Kettle near water	Electric shock	Keep the kettle base dry

Common mistakes

Comparing final temperatures when starting temperatures differ.
Saying insulation stops heat 'escaping' rather than reducing the rate of energy transfer.
Forgetting the unwrapped control beaker.

Worked analysis

Bubble wrap: 80.0 °C → 72.0 °C in 10 min, so the cooling rate = 8.0 ÷ 10 = 0.80 °C/min. Newspaper: 13.0 ÷ 10 = 1.3 °C/min. Bubble wrap reduces the rate of energy transfer more.

Common misconception

Insulation does not stop energy transfer completely; it reduces the rate of transfer.

Assessment coverage

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Retrieval cards

How do you compare insulators fairly?

Same volume and starting temperature of water, same beaker and thickness, then compare the drop in the same time.

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