P1.1.3 Energy Transfer by Heating Mr D Powell. Mr Powell 2012 Index Connection Connect your learning to the content of the lesson Share the process by.

P1.1.3 Energy Transfer by Heating

P1 PHYSICSMr D Powell

Mr Powell 2012Index

Connection

• Connect your learning to the content of the lesson

• Share the process by which the learning will actually take place

• Explore the outcomes of the learning, emphasising why this will be beneficial for the learner

Demonstration

• Use formative feedback – Assessment for Learning

• Vary the groupings within the classroom for the purpose of learning – individual; pair; group/team; friendship; teacher selected; single sex; mixed sex

• Offer different ways for the students to demonstrate their understanding

• Allow the students to “show off” their learning

Activation

• Construct problem-solving challenges for the students

• Use a multi-sensory approach – VAK• Promote a language of learning to

enable the students to talk about their progress or obstacles to it

• Learning as an active process, so the students aren’t passive receptors

Consolidation

• Structure active reflection on the lesson content and the process of learning

• Seek transfer between “subjects”• Review the learning from this lesson and

preview the learning for the next• Promote ways in which the students will

remember• A “news broadcast” approach to learning

Mr Powell 2012Index

Quick Summary....

Mr Powell 2012Index

P1.1.3 Energy Transfer by Heating

a) The transfer of energy by conduction, convection, evaporation and condensation involves particles, and how this transfer takes place.

b) The factors that affect the rate of evaporation and condensation.

c) The rate at which an object transfers energy by heating depends on:

■ surface area and volume ■ the material from which the object is made ■ the nature of the surface with which the object is in

contact.

d) The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating.

Mr Powell 2012Index

Quick Summary...

Look at this summary, write it down, but annotate it with diagrams to help explain it..

A

Mr Powell 2012Index

The role of free electronsin conduction through a metal.

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.

A

Mr Powell 2012Index

Candidates should understand the role of free electronsin conduction through a metal.

A. Outermost electrons wander freely through metal.

B. Metal consists of cations held together by negatively-charged electron "glue.“

C. Free electrons can move rapidly in response to electric fields, that's why metals are a good conductor of electricity.

D. Free electrons can transmit kinetic energy rapidly, hence metals are good conductors of heat.

The layers of atoms in metal are hard to pull apart because of the electrons holding them together, that's why metals are tough. But individual atoms are not held to any other specific atoms, it's why atoms slip easily past one another. Thus metals are ductile.

A

Mr Powell 2012Index

Conductors – Liquids v Solids!

With the exception of mercury, ALL LIQUIDS ARE POOR HEAT CONDUCTORS.

This is because the particles in liquids are Further apart than the particles in solids.

GASES are worse HEAT CONDUCTORS than liquids. They are good HEAT INSULATORS.

This is because The particles in gases are much further apart than they are in liquids.

A

Mr Powell 2012Index

Convection Currents

• A current, called a convection current becomes present in the liquid If thermal energy is supplied. The cooler liquid falls and Warmer, less dense liquid rises. The cycle continues as the heat is supplied. Energy is transferred.

• 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.

A

Mr Powell 2012Index

Radiators - Not Radiation but Convection!

• 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.

A

Mr Powell 2012Index

Thermometers.... LIT Think about a rise in air temperature causing a

thermometer to rise.

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, convection

Mr Powell 2012Index

Convection Currents Modelled by Peas.... D 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

Mr Powell 2012Index

Land & Sea Breeze - Extension

During the day the land.....

• heats up more quickly than the sea, so the air above the land warms up and rises.

• Cooler air from the sea • then flows in to replace • the warm, risen air and this creates what

we call a sea breeze.

At night the land cools....

• down more quickly than • the sea, so the air above • the sea is warmer and therefore rises. • Cooler air from the land • then flows out to • replace the warm, risen air and this creates

what we call a land breeze.

A

Mr Powell 2012Index

b) The factors that affect the rate of evaporation and condensation.

Evaporation: The particles in a liquid have different energies. Some will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have a lower average kinetic energy than before, so the liquid cools down as evaporation happens.

The rate of evaporation increases if....

• the temperature of the liquid is increased.• the surface area of the liquid is increased• Air is moving over the surface of the liquid.

Condensation: The particles in a gas have different energies.

Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down.

A

Mr Powell 2012Index

c) Cooling fins...

1. Lots of devices are made to cool faster by using “fins”

2. In fact we are increasing the surface area to allow more conduction, convection or radiation.

3. Some are also painted matt black for the best radiation!

A

Mr Powell 2012Index

Relative Ear Size...

The fennec fox lives in the desert and is adapted to cope with temperatures in excess of 45 °C. Relative to its body size, this creature has long legs, long muzzle and very large ears.

The enormous ears have a very large surface area to maximise the radiation of body heat and thus keep the animal cool.

In sharp contrast, the arctic fox has adapted to withstand temperatures of –40 °C and below. Again, relative to its size this fox has short legs, short muzzle and very small ears.

All of these adaptations give low surface area relative to body size and so minimise radiated heat loss.

Mr Powell 2012Index

d) The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating or cooling.

A

Time in minutes

Temperature of water in °C

Polartec 300 Polartec 200 Kitchen

Towel

0.0 83 81 820.5 78 76 751.0 74 72 711.5 72 67 682.0 72 67 653.0 72 65 614.0 71 63 545.0 70 61 506.0 69 58 457.0 68 57 408.0 67 56 359.0 66 55 3010.0 65 54 28

Try your own cooling curve experiment or plot these results...

Hint: do a scatter plot in landscape, then make a smooth LOBF

Mr Powell 2012Index

C, C& R Quick Questions

1 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....

D

Mr Powell 2012Index

C, C& R Quick Questions

1 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 2012Index

C, C& R Quick Questions

1 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

Mr Powell 2012Index

Question 1

Although 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

Mr Powell 2012Index

a) The transfer of energy by conduction, convection, evaporation and condensation involves particles, and how this transfer takes place.

b) The factors that affect the rate of evaporation and condensation.

c) The rate at which an object transfers energy by heating depends on:

■ surface area and volume ■ the material from which the object is made ■ the nature of the surface with which the object is in contact.

d) The bigger the temperature difference between an object and its surroundings, the faster the rate at which energy is transferred by heating.

How can you explain these things...

P1.1.3 Energy Transfer by Heating

C

Time in minutes

Temperature of water in °C

Polartec 300 Polartec 200 Kitchen

Towel

0.0 83 81 820.5 78 76 751.0 74 72 711.5 72 67 682.0 72 67 653.0 72 65 614.0 71 63 545.0 70 61 506.0 69 58 457.0 68 57 408.0 67 56 359.0 66 55 3010.0 65 54 28

Time in minutes

Temperature of water in °C

Polartec 300 Polartec 200 Kitchen

Towel

0.0 83 81 820.5 78 76 751.0 74 72 711.5 72 67 682.0 72 67 653.0 72 65 614.0 71 63 545.0 70 61 506.0 69 58 457.0 68 57 408.0 67 56 359.0 66 55 3010.0 65 54 28

Relative Ear Size?

P1.1.3 Energy Transfer by Heating

P1.1.3 Energy Transfer by Heating

P1.1.3 Energy Transfer by Heating