Q What does this picture show and who is in the best position?

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• Fluids ( ______ and ___) are poor _______, which is why ________ materials contain pockets of trapped air and other fluids can transfer ____ if they are free to ___.

Convection currents

Words – conductors, energy, insulating, move, gases, liquids.

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

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

heat

This cycle is called a convection current.

heat

Convection currents

Liquids and gases can both flow and behave in similar ways, so they are called fluids.

heatless dense

fluidThe heated fluid particles gain energy, so they move about more and spread out. The same number of particles now

take up more space, so the fluid has become less dense.

What happens to the particles in a fluid when it is heated?

What are the Keywords?

Warmer regions of a fluid are more dense than cooler regions of the same fluid.

called a convection current.

The warmer regions will rise because they are more dense.

The cooler regions will sink as they are less dense.

This is how heat transfer takes place in fluids and is called convection.

The steady flow between the warm and cool sections of a fluid, such as air or water, is

Convection in Liquids

Convection in Liquids

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Convection is the transfer of heat energy by the movement of matter."

Q) Why is the freezer compartment at the top of a fridge?

The freezer compartment is at the top of a fridge because cool air sinks.

This warmer air rises and so a convection current is set up inside the fridge, which helps to keep the fridge cool.

The freezer cools the air at the top and this cold air cools the food on the way down.

It is warmer at the bottom of the fridge.

Using Convection

Describe what is happening in these diagrams

Convection

Convection occurs in liquids and gases.

This is when heated stuff moves in bulk to a cooler region and takes the heat with it. The movement creates a convection current.

Currents are created as fluids rise when they are heated (they become less dense – particles are more spread out). They then fall when they cool down (they become more dense – particles are closer together).

What are the Keywords?

Questions– click here

1. What is convection? Explain in as much detail as you can.

2. Why doesn’t convection happen in solids?

3. If the heating is turned off on a day in winter, why is the coldest place in the room under a window?

4. Explain why smoke detectors are usually fitted to ceilings rather than walls?

5. A* Write a marketing brochure for a conservatory to explain how opening a roof vent near the top can help to cool the whole space. Use ideas from lesson 1.1, 1.3 to help.

If I am the answer, what is the Q?

ConductionConvectionRadiationInfrared

ConductorInsulator

Heat transferEvaporation

CondensationShiny surfaceMatt surface