Heat Energy Transfer

GCSE Physics

Textbook reference

• CCEA Physics, Page 17 – 25

• Key words list, what do you think the words and phrases mean?

• You don’t want to get confused… like President Bush!

Learning Intentions

• State the three types of heat energy transfer

• Recall in detail how the three types of heat energy transfer occur.

Don’t let the cold in!!!

Heat Transfer

• Heat Flow• Objects get hot if heat energy (thermal

energy) passes into them.  We know they get hot because the temperature rises.  It is important that we know the difference between temperature and heat:

• Temperature - the measure of how hot something is, measured in degrees Celsius;

• Heat - a flow of energy from a hot object to a cold object.  Heat is measured in joules (J).

Particle motion in a substance

Heat Flow

• Heat always flows from hot to cold.  Heat does not flow from a cold object to a hot object.  For example the heat from a hotplate passes into a cold pan to heat up the water in the pan.

• The greater the temperature difference between the hot object and the cold object, the greater is the flow of heat.

HOT HEAT COLD

Types of Heat Energy Transfer

• Page 17- The three ways in which heat can

move (types of heat energy transfer) are…

• ConductionConduction• ConvectionConvection• RadiationRadiation

Convection

10

Which weighs more?

Convection

• Structure of a Liquid and a Gas

Both states of matter flow and carry the heat energy with them.

Particles move feely

Gain heat energy

Move faster and spread out

Volume becomes

less dense

Rises and

bringing the heat

energy

What causes the convection currents?

The movement of hotter areas in a liquid can be seen using potassium permanganate as a dye:

H E A T

This cycle is called a convection current.

Can you explain how the convection current moves using the idea of density?

The diagrams on the left will help you.

Change in Density

14

Question Time

• CCEA Physics • Attempt Q 33 pg 24 and Q 5a pg 30

Conduction

Conduction

• Structure of a Solid (cannot flow)

Conduction in Solids

1919

Radiation

Application of Heat transfer

• Trapping layers of air in between bed sheets• Skin cancer• Cooking utensils• A greenhouse• Table mats, handles of cooking appliances • Air con is usually placed at the top of a room• A heating coil of a kettle is at the bottom• Formation of land and sea breezes• Silver Teapots and pans• Different hot and cold touch sensations from

objects• Colour and texture of clothing

Conduction, Convection or Radiation??

Newspaper Headlines!

24

26

Greenhouse Gases…

• Water Vapour

• Carbon Dioxide

• Methane

• Halocarbons

27

Questions

• Text Book pg 29• Questions 4 – 7

The internet can help!

• http://www.bbc.co.uk/climate/evidence/

• Evidence• Impacts• Adaptation

Reducing the runaway greenhouse effect

• http://www.bbc.co.uk/climate/adaptation/jack.shtml

• Life at Home• Copy down what we can do to help

slow this down!