Understanding Heat Transfer, Conduction, Convection and Radiation

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Water movement

Hot water rises

Cooler water sinks

Convection current

Cools at the surface

Slide 11

Why is it windy at the seaside?

Slide 12

Cold air sinks

Where is the freezer compartment put in a fridge?

Freezer compartment

It is put at the top, because cool air sinks, so it cools the food on the way down.

It is warmer at the bottom, so this warmer air rises and a convection current is set up.

Slide 13

The third method of heat transfer

How does heat energy get from the Sun to the Earth?

There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection.

?

RADIATION

Slide 14

Radiation

Radiation travels in straight lines

True/False

Radiation can travel through a vacuum

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False

Slide 15

Emission experiment

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

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.

shiny metal

radiation

dull black

emitting

Slide 16

Absorption experiment

Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes?

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 black

radiation

shiny metal

absorbing

Slide 17

Convection questions

Why are boilers placed beneath hot water tanks in people’s homes?

Hot water rises.

So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

Why does hot air rise and cold air sink?

Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.

Slide 18

Radiation questions

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.