Required Practical: Investigating Insulation

what is the 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

what is the independent variable?

Type of material

what is the dependent variable?

Temperature, T (°C)

what are the 3 control variables?

• Volume of water

• The temperature of the water at the start of the experiment

• The thickness of each material

how many pieces of equipment are needed?

8

list all the pieces of equipment needed

• small beaker

• large beaker

• kettle

• water

• thermometer

• piece of card with hold for thermometer

• at least 3 other different materials with a hole for the thermometer

• stopwatch

purpose of the small beaker

to hold the water and thermometer

purpose of the large beaker

to hold the small beaker inside and the materials placed on top

purpose of the kettle

to boil water

purpose of the water

substance to measure the temperature of

purpose of the thermometer

to measure the temperature of the thermometer

purpose of the card with the hole in it

to determine how good of an insulator it is

purpose of the other materials with a thermometer hole

to determine how good of an insulator they are

purpose of the stopwatch

to record how long it takes for the water to cool

what is the resolution of each piece of measuring equipment?

• Thermometer = 1 °C

• Stopwatch = 0.01 s

how many steps are there to the method?

6

step 1:

Set up the apparatus by placing a small beaker inside the larger beaker

step 2:

Fill the small beaker with boiling water from a kettle

step 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

step 4:

Record the temperature of the water in the small beaker and start the stopwatch

step 5:

Record the temperature of the water every 2 minutes for 20 minutes, or until the water reaches room temperature

step 6:

Repeat the experiment, each time changing the cardboard for another insulating material (in any order) and also without any insulation at all

what is the method of the experiment?

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

list the variables in a results table

time /mins → no. insulation → material 1 (temp) → material 2 (temp) → material 3 (temp) → material 4 (temp)

how would you analyse the 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

what should the graphs show?

The graphs should show that the temperature falls quickly at high temperatures, then more slowly (shown by the graph levelling out)

what conclusions should be drawn from the graph (3)

• When the water is at a high temperature, there is a greater temperature difference between it and room temperature. Therefore there is a greater energy transfer by heating

• When the water is at a low temperature, there is less temperature difference between it and room temperature. Therefore, there is a lesser energy transfer by heating

• The curve which takes the longest time for the temperature to drop is the shallowest

  • This material is the best insulator

what are 3 ways to prevent 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 that energy is transferred by conduction through the glass

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

suggest an alternative to the experiment to prevent systematic errors

• An alternative to 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

what are three random errors for this experiment?

• Make sure the hole for the thermometer isn't too big, otherwise, energy will be transferred through the hole

• Take repeated readings for each insulator

• Read the values on the thermometer at eye level, to avoid parallax error

what are 6 ways for 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

Why and how must the temperature, thickness of material and water volume be controlled (3)

• energy is transferred more quickly when the temperature difference between two substances is greater, so we have to control this by making sure that the initial temperature of the water is the same for each material we test.

• the thickness of a material affects its conductivity, so we need to control this by making sure that the materials we use are the same thickness.

• it takes longer for a larger volume of water to cool than for a smaller volume of water, so we need to control this by using the same volume of water for each material we test.

why do we have to control the factors that affect the dependent variable?

• By controlling the factors that affect the dependent variable, we are making sure that the investigation is a fair test and that the results are valid.

• If we fail to control these factors, then it would be impossible to tell if the results we get are because we changed the material or because of one of these other factors.