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Year 10
OCR
Foundation

Explaining convection

I can explain convection currents and describe how they can transfer energy.

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New
New
Year 10
OCR
Foundation

Explaining convection

I can explain convection currents and describe how they can transfer energy.

Download all resources
arrow-right
Share activities with pupils
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Lesson details

Key learning points

  1. Particles in a gas move very quickly in random directions and have empty space between them.
  2. Heating a fluid increases the speed of particles and they push each other further apart.
  3. As a fluid is heated, it becomes less dense.
  4. Hotter fluid rises through cooler fluid because it is less dense.

Keywords

  • Density - The mass per unit volume of a substance; a less dense substance will float on top of a more dense one.

  • Fluid - The term used for a gas or liquid because these can flow as their particles can move around.

  • Random motion - Describes the movement of particles in a fluid that travels at a range of speeds in all directions.

  • Convection current - The movement of fluids caused by differences in density within the fluid, which allows energy to be transferred as the hotter fluid rises to cooler areas.

Common misconception

Pupils often have the misconception that heat is a substance that can flow.

Focus learning on how heating causes particles to move more quickly, and the effects that this can have on the density of a fluid.

There are many different ways to demonstrate convection that can help pupils to understand convection. Challenge pupils to explain why the convection current occurs, and to explain this in their own words.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Gases and liquids can both flow. Because of this, they are both called .
Correct Answer: fluids, a fluid, fluid
Q2.
The mass per unit volume of a substance, or object, is called its .
Correct Answer: density
Q3.
A is two or more atoms that are bonded together.
Correct Answer: molecule
Q4.
Which of the following statements describe the particles in any gas?
All of the particles are identical to each other.
The particles are vibrating around fixed points.
Correct answer: The particles are in constant motion.
Correct answer: The particles are in random motion.
Correct answer: The particles are far apart compared to their size.
Q5.
Which of the following describes what happens to the particles of a gas when the temperature of the gas rises?
They get larger.
They get smaller.
Correct answer: Their average speed increases.
Their average speed decreases.
Q6.
A hot air balloon in air is staying at constant height. Which of the following statements about the average density of the balloon (including the basket, the balloon and the air inside) is correct?
It is less than the density of the surrounding air.
It is greater than the density of the surrounding air.
Correct answer: It is the same as the density of the surrounding air.

Exit quiz

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6 Questions

Q1.
Which of the following describe the motion of particles in a fluid?
All particles move at the same speed.
Correct answer: The particles have a range of different speeds.
All particles move in the same direction.
Correct answer: The particles move in random directions.
Q2.
Which of the following statements about the particles in air are correct?
Correct answer: The average speed of the particles is around 500 m/s.
The average speed of the particles is around 50 000 m/s.
Correct answer: If their average speed increases, the particles move farther apart.
If their average speed increases, the particles move closer together.
Q3.
Which of the following describes what happens to particles of a fluid when the temperature of a fluid decreases?
They become smaller.
They become heavier.
They move farther apart.
Correct answer: Their average speed decreases.
Correct answer: They collide with each other less frequently.
Q4.
Which of the following statements explains why convection can happen in a fluid?
Hotter fluid sinks because it is denser than cooler fluid.
Hotter fluid rises because it is denser than cooler fluid.
Hotter fluid sinks because it is less dense than cooler fluid.
Correct answer: Hotter fluid rises because it is less dense than cooler fluid.
Q5.
Sort the following statements into the correct order to explain how a hot air balloon can increase its height.
1 - The air inside is heated.
2 - This makes the air particles move faster and farther apart.
3 - This makes the air expand, so some particles are pushed out of the balloon.
4 - The air left inside the balloon is now less dense.
5 - This makes the average density of the balloon decrease.
6 - The balloon is now less dense than the surrounding air, so it rises upwards.
Q6.
A convection current occurs in a room after a radiator is switched on. Sort the following statements into the correct order to describe and explain how the convection current forms.
1 - The radiator heats the air around it.
2 - This makes the particles move faster and farther apart.
3 - This makes the air expand, so its density decreases.
4 - The air rises and spreads across the top of the room.
5 - It then cools, contracts and becomes more dense.
6 - It sinks towards the floor.