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# Heating And Cooling Lesson 3

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Science investigation on factors affecting cooling hot water

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### Heating And Cooling Lesson 3

1. 1. Heating and cooling <ul><li>Target </li></ul><ul><li>To investigate the factors that affect heat loss from hot water. </li></ul>Wednesday 25 November 2009
2. 2. The investigation <ul><li>In this investigation we will compare how convection affects the cooling of hot water. </li></ul>
3. 3. The experiment <ul><li>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). </li></ul><ul><li>Start measuring the temperature of the water every minute for ten minutes when the temperature of the water reaches 70 o C. </li></ul>
4. 4. The beakers <ul><li>Beaker 1. </li></ul><ul><li>Has 75 ml hot water with a lid. Heat loss by conduction only. </li></ul><ul><li>Beaker 2 </li></ul><ul><li>Has 75 ml water with no lid. Heat loss by conduction and convection. </li></ul>The results Now draw a graph of your results Time Lid on No Lid 0     1     2     3     4     5     6     7     8     9
5. 5. Time (minutes) 0 1 2 3 4 5 6 7 8 9 10 Temperature 0 20 40 80 Lid on No lid 60
6. 6. Analysing results <ul><li>1.What does the graph of your results show? </li></ul><ul><li>2.How do you explain, using scientific ideas, why the graph has this shape? </li></ul><ul><li>3.Was the investigation a success? Explain your answer. </li></ul><ul><li>4.How could it be improved? </li></ul>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.
7. 7. The investigation <ul><li>In this experiment we will investigate how a trapped air layer affects conduction of heat from hot water. </li></ul>
8. 8. The beakers <ul><li>Beaker 1. </li></ul><ul><li>Has 75 ml hot water with a lid. Single insulated. </li></ul><ul><li>Beaker 2 </li></ul><ul><li>Has 75 ml water with a lid and inside another beaker. Double insulated. </li></ul>The results Now draw a graph of your results Time Single Double 0     1     2     3     4     5     6     7     8     9
9. 9. Time (minutes) 0 1 2 3 4 5 6 7 8 9 10 Temperature 0 20 40 60 80 Double Single
10. 10. Analysing results <ul><li>What does the graph of your results show? </li></ul><ul><li>How do you explain, using scientific ideas, why the graph has this shape? </li></ul><ul><li>Was the investigation a success? Explain your answer. </li></ul><ul><li>How could it be improved? </li></ul>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.