Convection

Question 1

What states of matter does convection normally happen in?

Answer 1

Liquids and gases

Question 2

What allows liquids and gases to transfer heat by convection?

Answer 2

The particles in them are free to move about

Question 3

Convection is a much more ____ process than conduction

Answer 3

Convection is a much more effective process than conduction

Question 4

Define ‘convection’

Answer 4

Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.

Question 5

Describe how immersion heaters in kettles work

Answer 5

1. Heat energy is transferred from the heater coils to the water by conduction (particle collision)
2. The particles near the coils get more energy so start moving around faster
3. This means that the water expands and gets less dense, as there is more space between the particles
4. This reduction in density means the hot water tends to rise above the denser, cooler water
5. As the hot water rises it displaces the colder water out of the way, making it sink towards the heater coils
6. This cold water is then heated by the coils, and the cycle begins again, causing a convection current, circulating the heat energy through the water

Question 6

What shaped container is convection most efficient in?

Why?

Answer 6

Roundish or square containers

Becaus they allow convection curretns to work best

Question 7

Will the water below a heater rise?

Answer 7

No, because it won’t get the heat energy transferred by the heater, and won’t be part of the convection current

Question 8

What are convection currents all about?

Answer 8

Changes in density

Question 9

Describe the test for convection using potassium permanganate crystals

Answer 9

Put them at the bottom of a beaker of cold water

Heat it gently over a Bunsen flame

The potassium permaganate starts to dissoolve and make a bright purple solution that gets moved around the beaker by the convection currents as the water heats