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29/09/2016 Methods of Heat Transfer By the end of the lesson you should be able to: Explain how tinned peas warm up in a pan Why robins don’t freeze in.

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Presentation on theme: "29/09/2016 Methods of Heat Transfer By the end of the lesson you should be able to: Explain how tinned peas warm up in a pan Why robins don’t freeze in."— Presentation transcript:

1 29/09/2016 Methods of Heat Transfer By the end of the lesson you should be able to: Explain how tinned peas warm up in a pan Why robins don’t freeze in winter Key words: (Can you think what they might mean?) Conduction Convection Radiation Insulation -Write down today’s title, lesson objectives, key words and the date. Draw the picture -> -> -> -> -> -> -Underline all of your work

2 How do our peas cook? How does heat energy travel from the hob to the peas?

3 Conduction How do different solids and metals compare? => Demo time…… Conduction is the transfer of heat energy from a hotter to a colder region Particles vibrate, transferring energy to their neighbours, which in turn vibrate too. The thermal energy moves, but the particles stay put. Heat energy transfers best in solids – why is this true? Poor conductors are also called insulators Thermal Energy

4 Poor Conduction In this experiment we saw that liquid water is a poor conductor of heat. The ice cube did not melt even though the water above it was boiling. Air is also a poor conductor of heat. This is how many types of house insulation and clothing keep us warm.

5 Convection 29/09/2016 How does a lava lamp work? Use these words in your explanation: Density Rising/falling Cooler/hotter Expansion/contraction

6 Convection Gases and liquids When a liquid or gas is heated the hotter liquid/gas rises The cooler liquid/gas moves in to replace it This is a convection current

7 29/09/2016 Convection Convection is all about when a gas or liquid (“fluid”) moves and carries heat energy with it. When the fluid is heated it ____________. This means that it will become less __________ than the colder fluid around it. As a result, the warmer fluid will try to “_______” over the colder fluid, and this is why warm air rises. This is called a convection ___________ and is how heat reaches us from the ___________ in this room. Words to use: expands, radiators, dense, heated, current, float

8 How is convection helping here?

9 Off and Onshore Breezes

10 Other examples of convection What about in central heating?

11 How does the sun’s heat energy reach us? Why are some houses painted white?

12 Radiation Everything gives off heat radiation. The hotter the object, the greater the energy of the radiation. It travels as a wave in a straight line and needs no particles to help it move, so can travel through the vacuum of space. radiationgreater particles vacuum

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14 Draw a diagram to show the ‘tin lid demonstration’ and then complete the sentences below: Investigating how different surfaces absorb heat energy: One tin lid was painted with ______ paint whilst the other was unpainted and had a ________ metal surface. Each tin lid was held at _______distance from a blue Bunsen flame. This means that each lid receives the _______amount of heat energy. The lids absorb heat energy radiated from the flame. This heat energy is transferred through the lid by ___________ and causes the wax to ____. The more rapidly the lid absorbs heat, the more rapidly the wax will melt.

15 How does a thermos flask work? Stopper Vacuum Glass Hot liquidSilvered Surfaces Glass Hot liquid This is your prep!

16 Radiation Conduction Convection Atmosphere – A gas Space – A vacuum Alien - solid How does the sun’s energy reach us?

17 Electric Bar Heater – just radiation here?

18 Of course not!!! Radiation Conduction Convection Silvered surface

19 ConductionConvectionRadiation electric bar heater ☺☺ fan heater blowing hot air ☺ radiator☺☺ saucepan on electric hob ☺☺☺ White Boards: What is the MAIN method of heat transfer

20 How is insulation working here? 29/09/2016

21 Conductors or insulators? School Jumper TableWater Air Plastic Metal

22 29/09/2016 Pick one to describe How best to insulate a house against heat loss by convection, radiation and conduction How do birds keep warm? How the sun’s heat energy reaches us Why houses in Greece are often white Why wearing white in summer is better than black What are off and onshore breezes How do hail stones are able to grow in size within a cloud Why large birds hover over motorways Why do metals get hotter faster than plastic?

23 Check your learning Different surfaces absorb and radiate heat energy at different rates. Darker colours radiate and absorb heat energy more rapidly than lighter colours. Black surfaces radiate/absorb most rapidly. Matt surfaces radiate/absorb heat energy more rapidly than shiny surfaces.


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