P1a Energy & Energy Resources Mr D Powell. Mr Powell 2008 Index Heat Transfer p226-241 1 1.

P1a Energy & Energy Resources

KS4 CORE SCIENCEMr D Powell

Mr Powell 2008Index

Heat Transfer p226-241

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heat is transferred in and out of bodies and we can reduce the rate of transfer by using insulation.

Thermal (infra red) radiation is the transfer of energy by electromagnetic waves. All bodies emit and absorb thermal radiation and the hotter a body is the more

energy it radiates. Dark, matt surfaces are good absorbers and good emitters of radiation. Light, shiny surfaces are poor absorbers and poor emitters of radiation.

S Explain that the shape and dimensions of a body affect the rate at which it transfers heat.

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The transfer of energy by conduction and convection involves particles and how this transfer takes place.

The bigger the temperature difference between a body and its surroundings, the faster the rate at which heat is transferred.

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1.1 Thermal Radiation p228

Thermal (infra-red) radiation is the transfer of energy by electromagnetic waves.

All bodies emit and absorb thermal radiation.

The hotter a body is the more energy it radiates.

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Thermal Radiation Quick Questions1 Where does this planet get its energy from?

2 What does a prism do to white light?

3 What is the rough temperature of the surface of the sun?

4 What does thermal mean?

5 What is infra red radiation?

6 Why is infra red radiation captured by the atmosphere and not UV or visible

7 How can we reduce the greenhouse effect?

8 How can you tell if a metal is very hot

9 Do all objects give out thermal radiation

10 Do all objects absorb thermal radiation

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Thermal Radiation Quick Questions1 Where does this planet get its energy from? Sun

2 What does a prism to do white light? disperse it

3 What is the rough temperature of the surface of the sun? 5500C

4 What does thermal mean? heat

5 What is infra red radiation? thermal radiation beyond visible red light

6 Why is infra red radiation captured by the atmosphere and not UV or visible (A*-C) it has a longer wavelength

7 How can we reduce the greenhouse effect? reduce emissions of certain gasses like methane, CO2

8 How can you tell if a metal is very hot glows brightly

9 Do all objects give out thermal radiation yes

10 Do all objects absorb thermal radiation yes

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Seeing at Night

1. Can you identify the objects?

2. Now write down a list and explain which parts are hot parts compared to the cold parts?

3. Why might this be?

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Energy Movement

1. Watch the FLV of the snapshots shown.

2. For each one explain what you are seeing in terms of energy transfers. Pouring water

Breast ExamsThermometers

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Temperature & Colour Theory.... The main frequency (or colour) of emitted radiation

increases as the temperature increases.

For example, a red hot object radiates most in the long wavelengths of the visible band, which is why it appears red. If it heats up further, the main frequency shifts to the middle of the visible band, and the spread of frequencies mentioned in the first point make it appear white.

We then say the object is white hot..

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Order of Temperature In a team sequence

these images into an order for which is hottest and which is coolest. Try and work out what the clues were

SparklerLight bulbIce waterSunSunny dayFire

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Order of TemperatureIce water 0

Sunny day 23

Light bulb 247

Fire 500

Sun 5500

Sparkler 1000-1600

Make sure your write out the list and put a reason to explain why you put them in this order.....

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Homework...Infra-red satellite imagery is used in weather forecasting and analysis of land use.

Investigate how IR satellites are used to monitor the weather and to analyse how land is used in different countries.

Find out how different types of vegetation or habitation show up in infra-red imagery or even other parts of the electromagnetic spectrum.

There are many excellent images available to explore on the Internet; you could start with the various ‘land sat’ or weather forecasting web sites.

Write up: Produce a paragraph of your findings with any diagrams or pictures you can print off.

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1.2 Surfaces & Radiation p230

Dark, matt surfaces are good absorbers and good emitters of radiation.

Light, shiny surfaces are poor absorbers and poor emitters of radiation.

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Groups?

1. In a team group these images to reflect their energy characteristics.

2. Elect a spokesperson to explain why you have done this!

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Theory of EM Radiation EM radiation is produced by objects all the time even

though they don’t appear to be doing much.

It is in fact internal energy from the object converted to either visible EM radiation i.e. ROY-G-BIV or non visible light Infra red.

It is the infra red part that makes them feel hot!

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Absorption & Emission of EM Radiation

1. A perfect black object absorbs all the visible light and IR then emits the IR really well. It feels hotter to the touch

2. A perfect white object reflects all the colours and IR and UV radiation. It feels cooler to the touch.

3. A good example is white lines on our roads...or a t-shirt

4. Look at the demo of shiny v matt for visible light as an example!

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Shiny or Dull Theory...

1. A mirrored surface reflects all the radiation striking it and absorbs none. Therefore a mirror cannot emit large amounts of radiation.

2. A matt dull surface absorbs more radiation due to cavities in the surface. (crevices)

3. A polished ring will be cooler than a dull one.

Extension TASK – Now answer the questions on page 213

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Solar PanelsNow you have listened to your teacher explain how a solar panel works make up your own flowchart to explain the process (including diagrams).

Fill in as much detail as you can and use as many steps you as want!

Extension Task

Now imagine you science consultant who designed the panels got his science the wrong way around. What mistakes could he have made to make the panel useless!

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Leslie Cube...

You an investigate the whole process by using a Leslie Cube...

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Reflectors & Absorbers...

5 mins later

5 mins later

Dark matt surfaces emit (give out) more radiation…than light shiny surfaces at the same temperature.

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Reflectors & Absorbers...

Dark matt surfaces are better absorbers (poorer reflectors) of radiation…than light shiny surfaces at the same temperatures.

5 mins later

5 minslater

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The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.

Emission experiment...

Four containers were filled with warm water. Which container would have the warmest water after ten minutes?

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Shiny metal

Dull metal

Dull black

Shiny black

shiny metal

radiation

dull black

emitting

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Absorption experiment...

Four containers were filled with warm water. Which container would have the warmest water after ten minutes?

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Shiny metal

Dull metal

Dull black

Shiny black

The __________ container would be the warmest after ten minutes because its surface absorbs heat _________ the best. The __________ container would be the coolest because it is the poorest at __________ heat radiation.

dull blackradiation

shiny metalabsorbing

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Decisions See if you can you sort these in the correct order of which

would be the best absorbers of heat....

Shiny Black CarShiny Steel CarDull Black CarBrushed Steel Car

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Dull Black CarShiny Black CarBrushed Steel CarShiny Steel Car

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1.3 Conduction p232

The transfer of energy by conduction . . . involves particles and how this transfer takes place.

The bigger the temperature difference between a body and its surroundings, the faster the rate at which heat is transferred.

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Atomic Structure M• Everything is made up of molecules.

• Molecules are not the same.

• Plastic is made of thousands of atoms.

• Glass is made of just three.

• Metals are never made of molecules but always single atoms.

• This is why they behave differently

• They all have unique properties

Glass MoleculePlastic Molecules

Metal atoms7 mins

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What are electrons… M

7 mins

• Smallest thing you can think of is an Atom. But we can go deeper than that.

• But most of it is space!

• Most of the mass is the nucleus in the middle. • Tiny electrons orbit the nucleus and that forms the atom

• They almost form a shell around it as they travel so fast (tennis balls and boy)

• Electrons are held by forces inside the atom

• The nucleus is very tiny

• A whole atom is a lot bigger than the nucleus7 mins

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Conduction M

7 mins

• Stir a boiling liquid with a plastic ladle after a while it will become warm. So will a wooden ladle.

• However, a metal ladle will quickly burn your hands.

• All these materials conduct heat at different rates

• Molecules or Atoms bumping at speed into their neighbours transmit the energy.

• It is like a row of dominos

• Free electrons can travel to move extra energy

• They give the atoms extra vibrational energy.

• This makes all metals a good conductor because of their structure

7 mins

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What is Conduction.. M

7 mins

• On your printed sheet try and examine the information you have been given both visually, orally and in written form. Answer the three questions on the sheet. There is space for a diagram as well. Continue onto the back of your sheet if you feel the need to.

1. What happens?

2. Why does it happen?

3. How does it happen?

1 2 3

A good answer will have to include;

o Ideas of atoms / molecules

o Structure of atoms & electrons

o Movement of electrons/ energy

o Ideas of vibrational energy 10 mins

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Heat Transfer in a Solid by Conduction...Heat energy can move through a substance by conduction. Metals are good conductors of heat, but non-metals and gases are usually poor conductors of heat. Heat energy is conducted from the hot end of an object to the cold end.

The electrons in piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now charged metal ions. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These move through the structure of the metal, colliding with ions as they go.

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Quick Fire Questions1. Wood is a fossil fuel.

2. Oil is formed from dead plants being crushed under huge pressure.

3. Heat transfers through plastics more easily as they have lots of free electrons.

4. Carpet is a poor conductor as it has no free electrons.

5. Energy travels through roof tiles by conduction.

6. Metals are good conductors as they have lots of free electrons.

7. Energy does not travel by conduction through space.

8. A wooden spoon is a good conductor of heat and electricity

9. Metals have a structure like a single molecule

10. Glass has a structure made of three atoms which makes it a poor conductor

True

False

False

False

False

True

True

True

True

True

5-8 mins

A* = 10

A = 9

B = 8

C = 7

D = 6

E = 4-5

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1.4 Convection p234

The transfer of energy by convection involves particles and how this transfer takes place.

Under similar conditions different materials transfer heat at different rates.

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C, C& R Quick Questions1 Metals transfer heat by.....

2 Liquids and gases transfer heat mainly by.....

3 Light is the transfer of energy by.......

4 Free electrons moving through a substance indicate that it is a....

5 What place would you tap water off a hot water tank & why...

6 The sea breeze in the daytime is towards the..

7 Why does a vacuum flask keep you tea hot?

8 Why are radiators painted white instead of dull black?

9 What effect does cavity wall insulation stop completely.

10 Loft Insulation works by....

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C, C& R Quick Questions1 Metals transfer heat by..... Conduction

2 Liquids and gases transfer heat mainly by..... Convection

3 Light is the transfer of energy by....... Radiation

4 Free electrons moving through a substance indicate that it is a.... Conductor with metallic structure

5 What place would you tap water off a hot water tank & why... At the top as hot water rises (Convection)

6 The sea breeze in the daytime is towards the..

7 Why does a vacuum flask keep you tea hot?

8 Why are radiators painted white instead of dull black?

9 What effect does cavity wall insulation stop completely.

10 Loft Insulation works by....

Mr Powell 2008Index

C, C& R Quick Questions1 Metals transfer heat by..... Conduction

2 Liquids and gases transfer heat mainly by..... Convection

3 Light is the transfer of energy by....... Radiation

4 Free electrons moving through a substance indicate that it is a.... Conductor with metallic structure

5 What place would you tap water off a hot water tank & why... At the top as hot water rises (Convection)

6 The sea breeze in the daytime is towards the.. Land as it heats up more quickly than the water (Convection)

7 Why does a vacuum flask keep you tea hot? The energy cannot conduct through a vacuum

8 Why are radiators painted white instead of dull black?

So that the heat is not all conducted out of the first radiator in the system!

9 What effect does cavity wall insulation stop completely. Convection Currents in the cavity

10 Loft Insulation works by.... Trapping hot air in the fibres to reduce conduction and convection

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What is convection

• This is the way heat is transferred in liquids and gases.

• It depends on, in general, fluids expand when heated and become less dense.

• This is a domestic hot water tank.

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Convection Currents

• A current, called a convection current becomes present in the liquid If heat is supplied.

• Cooler liquid falls.

• Warmer, less dense liquid rises.

• The cycle continues as the heat is supplied

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The Earth’s Crust...

• The Earth’s lithosphere (the crust) is cracked into a number of large pieces (tectonic plates) which are constantly moving.

• This is as a result of convection currents within the Earth’s mantle driven by heat released by natural radioactive processes.

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Radiators

• The heat from a radiator causes the warm air to rise and as the air rises then it cools and becomes denser.

• The cool air falls and replaces the warm air which is rising.

• And the cycle continues until the radiator cools.

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Thermometers.... S Can you explain what is happening here in terms of

particle behaviour in as much detail as possible. Write your own paragraph and diagrams to help you.

You might want to start like this...

We can see that......This is because.......Firstly the.....Secondly the.....Thirdly the.....In conclusion......

Key Words:

Particles, Temperature, Kinetic Energy, Thermal, Heat, Expansion

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Convection Currents Modelled by Peas.... M Can you explain what is happening here in

terms of particle behaviour in as much detail as possible. Write your own paragraph and diagrams to help you.

You might want to start like this...

We can see that......This is because.......Firstly the.....Secondly the.....Thirdly the.....In conclusion......

Key Words:

Particles, Temperature, Kinetic Energy, Thermal, Heat, Expansion, rises, falls

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Creative Writing

Firstly watch the FLV movie on Convection.

As you are watching the movie make some short hand notes to remind you of what you have seen.

Now use this and the items you have covered in the lesson to write a structured set of paragraphs and diagrams which comprehensively explains the term “Energy Transfer by Convection”

You can also use anything else you can thing of to add to this!

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Question 1Although we have not talked about all types of energy transfer can you fill in some of the blanks for this question. Try and reason out the missing ones?

electrons

ionscollisions

waves

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Question 2

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Question 3

matt surfaces

shiny surfaces

Infra red

particles

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Thermal Radiation Quick Questions1

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