HEAT ENERGY AND ITS TRANSFER

2. HEAT TRANSFER BYCONVECTION

Learning Points1. State that heat flows through

gases by convection currents.

1. Give examples of everyday uses of convection currents.

Convection

• Convection takes place in liquids and gases.

• Convection will not take place in solids because the particles are too close together and can only move a little bit.

Convection currents in gases

1. Cut out the paper spiral and tie on a piece of thread.

2. Hang it above a turned on light-bulb.

3. Watch and describe what happens.

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Convection currents in gases

Hot, less dense air rising.

It catches the paper spiral and starts to turn it around.

• Convection currents produce sea breezes.

Convection currents and weather

During the day

During the day, the land heats up faster than the sea. Air above the land is heated. It expands and rises up. The cold air above the sea then moves inland to take its place, thus creating a sea breeze.

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Convection currents and weather

During the night

At night, the sea temperature drops slowly as compared to the land which cools rapidly. The sea is now warmer than the land. The warm air rises above the sea and cool air above the land moves out to take its place and a land breeze is created.

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Convection currents in the home

The less dense gas will now rise and the cooler gas or will move in and take its place.

A heater works by heating up the gases in the air around it. The gas particles vibrate and start to move further apart making them less dense.

Convection currents in the home

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Fridge

Air conditioner

Place the Statements in order

In Convection:1. The less dense fluid rises.2. When a substance is heated it

expands.3. The warm fluid is therefore less

dense.4. When it reaches the top it cools

and contracts.5. The more dense fluid sinks.6. The cycle of rising and falling is

the convection current.

1

2

3

4

5

6

All c’s: Fill in the blanks.

• Heat flows through solids by c__________.

• Liquids and gases are poor c_________ but transfer heat by c___________.

• We make use of these c_________ currents in kettles, c___________ heaters and when cooking.

onduction

onductors

onvection

onvectiononvectio

n

1 minute to complete!

• Come up with as many uses for and examples of convection as you can! You have one minute.

Ocean currents, predicting the weather, boiling a kettle, boiling an egg, heating a room, causing the weather, moving continents, causing volcanoes…