PAG: Investigating Insulation (OCR Gateway GCSE Physics: Combined Science)

Aim of the Experiment

• The aim is to investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material
• This is only one way this experiment could be carried out
  • Another version would be to use copper cans and wrap them in different insulating materials

Variables:

• Independent variable = Time, t (s)
• Dependent variable = Temperature, T (°C)
• Control variables:
  • Volume of water
  • The temperature of the water at the start of the experiment
  • The thickness of each material

Equipment List

• Resolution of measuring equipment:
  • Thermometer = 1 °C
  • Stopwatch = 0.01 s

Method

1. Set up the apparatus by placing a small beaker inside the larger beaker
2. Fill the small beaker with boiling water from a kettle
3. Place a piece of cardboard over the beakers as a lid. It should have a hole suitable for a thermometer and place the thermometer through this hole and into the water in the small beaker
4. Record the temperature of the water in the small beaker and start the stopwatch
5. Record the temperature of the water every 2 minutes for 20 minutes, or until the water reaches room temperature
6. Repeat the experiment, each time changing the cardboard for another insulating material (in any order) and also without any insulation at all

• An example of a table of results may look like this:

Analysis of Results

• Plot a graph of temperature against time and draw a curve of best fit
  • Plot all the curves for each material on the same axis

• An example graph might look like this:

• The graphs should show that the temperature falls quickly at high temperature, then more slowly (shown by the graph levelling out)
  • When the water is at a high temperature, there is a greater temperature difference between it and room temperature. This creates a high rate of energy transfer
  • When the water is at a low temperature, there is less temperature difference between it and room temperature. This creates a low rate of energy transfer

• The curve which takes the longest time for the temperature to drop is the shallowest
  • This material is the best insulator

Evaluating the Experiment

Systematic Errors:

• Make sure the starting temperature of the water is the same for each material since this will cool very quickly
  • It is best to do this experiment in pairs to coordinate starting the stopwatch and immersing the thermometer

• Only the top of the beaker is covered, so heat escapes through the sides of the beaker, an alteration of this experiment could be:
  • Putting the insulating materials around the beaker as well as on top of it
  • Using one material with different thicknesses. This will show that the thicker the material, the better the insulation

• Use a data logger connected to a digital thermometer to get more accurate readings

• Make sure the hole for the thermometer isn't too big, otherwise the heat will escape through the hole
• Take repeated readings for each insulator
• Read the values on the thermometer at eye level, to avoid parallax error

Safety Considerations

• Keep water away from all electrical equipment
• Make sure not to touch the hot water directly
  • Run any burns immediately under cold running water for at least 5 minutes

• Do not overfill the kettle
• Place the small beaker inside the large beaker first before pouring water in, since the small beaker will become very hot
• Make sure all the equipment is in the middle of the desk, and not at the end to avoid knocking over the beakers
• Carry out the experiment only whilst standing, in order to react quickly to any spills