Particles on the move

• Physics
• Secondary Education
• Age 12,13

23 March 2023

3.7 Particles on the move

Content objectives

• describe diffusion in terms of particle theory
• explain how diffusion happens in gases
• explain how diffusion happens in liquids
• explain that the speed of diffusion is affected by the change in concentration
• explain that the speed of diffusion is affected by the change in temperature

Let's recall

Key Question 1

How would you know if someone is cooking food in your kitchen without really going to the kitchen?

Key Question 2

When you pour orange juice into the water, why does all the liquid eventually turn orange?

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A gas particle moves randomly.

I agree.

I disagree.

The speed and direction of particles are constant (not changing).

I agree.

I disagree.

What happens when you mix two gases in one container?

Which of the following terms is used to describe what happens to the particles of both gases mixed in one container?

1. disappear
2. doubled in number
3. spread out

What term is used to describe the overall random movement of particles from an area of high concentration to a lower concentration of particles?

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Key Question 3

What happens when you heat up the particles of a liquid?

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What happens when you heat up the particles of a liquid?

Lesson Summary

• Diffusion happens when particles of gases and liquids move randomly from a higher concentration to a lower concentration.
• When two gases are mixed in a container, the particles of each gas spread out randomly in the container over a period of time.
• The bigger the difference in concentration, the faster the diffusion of gases or liquids.
• The higher the temperature, the faster the diffusion because the particles have more energy to move.