Heating and cooling

Target

To investigate the factors that affect heat loss from hot water.

Saturday 22 April 2023

The investigation

In this investigation we will compare how convection affects the cooling of hot water.

The experiment

• Set up two small beakers which contain hot water- one has a lid (loses heat by conduction only) and the other does not (loses heat by conduction and convection).

• Start measuring the temperature of the water every minute for ten minutes when the temperature of the water reaches 70oC.

The beakers Beaker 1. Has 75 ml hot water with a

lid. Heat loss by conduction only.

Beaker 2 Has 75 ml water with no lid.

Heat loss by conduction and convection.

Time Lid on No Lid

0    

1    

2    

3    

4    

5    

6    

7    

8    

9    

The results

Now draw a graph of your

results

Time (minutes)

0 1 2 3 4 5 6 7 8 9 10

Temperature

0

20

40

80

Lid on

No lid

60

Analysing results• 1.What does the graph of your results show?• 2.How do you explain, using scientific ideas, why

the graph has this shape?• 3.Was the investigation a success? Explain your

answer. • 4.How could it be improved?

1. Beaker with lid on cools slower than the one with no lid.

2. The lid stops heat being lost by convection so the rate of heat loss is slower. Both beaker lose heat by conduction.

The investigation

In this experiment we will investigate how a trapped air layer affects conduction of heat from hot water.

The beakers Beaker 1. Has 75 ml hot water with a

lid. Single insulated.

Beaker 2 Has 75 ml water with a lid and

inside another beaker. Double insulated.

Time Single Double

0    

1    

2    

3    

4    

5    

6    

7    

8    

9    

The results

Now draw a graph of your

results

Time (minutes)

0 1 2 3 4 5 6 7 8 9 10

Temperature

0

20

40

60

80

Double

Single

Analysing results

• What does the graph of your results show?

• How do you explain, using scientific ideas, why the graph has this shape?

• Was the investigation a success? Explain your answer.

• How could it be improved?

1. The double insulated beaker cools much slower than the single insulated one – this shows that the air trapped between the glass keeps insulates the container.

2. Air is a poor conductor of heat the air between the glass cannot escape so the water in the beaker stays hot.