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# Heating And Cooling L1

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Heat and temperature Year 8 Lesson 1

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### Heating And Cooling L1

1. 1. Heating and cooling <ul><li>Target </li></ul><ul><li>To know the difference between heat and temperature and to know more about the Celsius temperature scale. </li></ul>Thursday 29 October 2009
2. 2. It takes 2 minutes to heat the water in the kettle to 100 o C. It takes 2 hours to heat the water in the hot water tank to 60 o C. The tanks needs far more HEAT energy than the kettle because there is so much more water.
3. 3. Heat and temperature <ul><li>Heat and temperature are not the same thing. </li></ul><ul><li>Heat is a form of energy it is measured in Joules. </li></ul><ul><li>Temperature is a measure of the level of heat. It is measured in degrees Celsius. ( o C) </li></ul>
4. 4. Heat and temperature <ul><li>In this experiment the coin is very hot (about 800 o C) but it has very little heat. When the coin is submerged in the cold water the heat is taken up in the water. There is so little heat transferred the temperature of the water rises less than 1 o C. </li></ul>
5. 5. The Celsius scale <ul><li>The temperature scale in Celsius was created by taking frozen ice to be 0 o C and boiling water to be 100 o C. </li></ul><ul><li>This picture shows the world’s largest thermometer. </li></ul>
6. 6. The freezing point of water <ul><li>A temperature of 0 o C is the temperature at which water freezes at sea level air pressure. </li></ul><ul><li>However ice will freeze below 0 o C if salt is added to it. As shown in the experiment where salt is added to a funnel containing ice. The temperature drops to about -14 o C. </li></ul>
7. 7. The freezing point of water <ul><li>However ice can freeze below 0 o C if it is subjected to high pressure as shown in the experiment where a wire caring a heavy weight is suspended over the block of ice. </li></ul><ul><li>The wire passes through the ice leaving a solid block behind. </li></ul><ul><li>The ice below the wire melts under high pressure but then freezes again once the wire passes though and the pressure drops. </li></ul>
8. 8. The boiling point of water <ul><li>The boiling point of water is 100 o C at sea level pressure of air. </li></ul><ul><li>The boiling point rises if the air pressure rises. </li></ul><ul><li>In past times (before microwave ovens) people used to cook food in pressure cookers – the boiling water was above 100 o C so the food cooked faster. </li></ul>
9. 9. The boiling point of water <ul><li>Water boils well below 100 o C when the pressure drops as shown in the experiment where a flask of boiling water is sealed and inverted. </li></ul><ul><li>The pressure drops because water vapour takes up a lot of the space inside the flask, when the flask is cooled the water vapour condenses and the pressure drops. </li></ul><ul><li>The graph shows how low the boiling point can drop at low pressures. </li></ul>
10. 10. The boiling point of water <ul><li>Explain why the coffee is always cold on Mount Everest! </li></ul>
11. 11. Temperature ranges <ul><li>The thermometer shown give an idea of some possible temperatures. </li></ul><ul><li>Day temperatures in the UK can vary from –10 o Cto 35 o C. </li></ul>
12. 12. Temperature ranges <ul><li>The hottest temperature ever recorded was 58 o C in Libya (1922) and the coldest -89 o C in Antarctica (1983). </li></ul>
13. 13. Global warming <ul><li>These photographs show how the Arctic ice cap has melted from 1979 to 2003. </li></ul>1979 2003
14. 14. Homework questions Hodder B –Page 29
15. 15. Questions – Core Science 1 – pages 108 and 109 <ul><li>1. Temperature rises as water is heated at first. </li></ul><ul><li>2. Temperature stays the same when water is boiling. </li></ul><ul><li>3. Temperature stays the same. </li></ul><ul><li>4. A and B melt (in warmer surroundings) C stays frozen (in very cold surroundings). </li></ul><ul><li>5. B takes longer to melt because the air temperature is not as hot. </li></ul><ul><li>6. Water mass is less after one week. </li></ul><ul><li>7. Hair dryer is warm air and moving air – both help to evaporate water. </li></ul><ul><li>8. Sunny and breezy dry faster – warm moving air dries the clothes faster. </li></ul><ul><li>9. Person soaked in water feels coolest because evaporation causes cooling. </li></ul><ul><li>10. Sweating produces water on the skin which will cool the body as it evaporates. </li></ul>