Thermal insulation

1 Plan and risk assessment

Hot water transfers energy to its cooler surroundings, faster the hotter it is. An insulator, with a low thermal conductivity and trapped air, lowers the rate of energy transfer, so the water cools more slowly. The drop in temperature in the same time compares how well each material insulates.

ΔE = m c Δθ

Prediction

2 Apparatus

• Kettle Boils the water.
• Beakers: 100 ml, 250 ml and 800 ml Hold the hot water; the 800 ml beaker holds the insulation around the 100 ml one.
• Measuring cylinders (100 ml and 250 ml) (resolution 1 ml (100 ml), 2 ml (250 ml)) Measure the same volume of water for every beaker: 80 ml in the 100 ml cylinder, 200 ml in the 250 ml one.
• Two thermometers (digital or liquid-in-glass) (resolution 0.1 °C or 1 °C) Measure the temperature of the water in each beaker.
• Two stopwatches (resolution 0.01 s) Time the 5-minute readings for each beaker.
• Cardboard lids with a hole Cover the beakers; the thermometer goes through the hole.
• Insulating materials and rubber bands Bubble wrap, polystyrene granules, sawdust, corrugated card and newspaper.
• Heatproof mats and a tray Protect the bench; catch spilt granules.

3 Method

Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.

Anomalies

Ring any anomalous result. Say what probably went wrong and whether you repeated it.

6 Analysis

1. Drop in temperature: beaker A

   drop in temperature = temperature at 0 min − temperature at 20 min

   Answer

2. Drop in temperature: beaker B

   drop in temperature = temperature at 0 min − temperature at 20 min

   Answer

3. Energy transferred from beaker B

   ΔE = m c Δθ (c of water = 4200 J/kg °C)

   Answer

4. Where the energy goes

   Answer

7 Conclusion and evaluation

Conclusion

Sources of error

For each, say whether it is systematic or random, and how it affected your results.

Improvement