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IGCSE Chemistry Revision Notes Diffusion

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Topic: States of matter

Sub Topic: 1.1 Solids, liquids and gases / Diffusion

IGCSE Chemistry Revision Notes Diffusion

Free download IGCSE Chemistry Diffusion Notes 2024 to 2028 Exams

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IGCSE Chemistry Solved Past Paper Question Diffusion

Observations

The white ring is formed at C because ethylamine is less dense (lower Mr) than HBr.
Hence ethylamine diffuses faster than HBr.

Why do the gases diffuse? (Kinetic theory explanation)

Gases diffuse because their particles move randomly and collide with each other. This movement causes particles to spread from a region of high concentration to a region of low concentration.

Diffusion happens faster in warmer temperatures than in cooler temperatures.

IGCSE Chemistry Diffusion / Test Yourself

Summary Fill in the Blanks

Click the highlighted blanks to reveal key ideas about diffusion. Headings are retained and the blanks are designed for IGCSE Chemistry level.

1 Definition of Diffusion

Diffusion is the

________________ random

movement of particles from an area of high concentration to an area of low concentration.

This movement takes place down the concentration

________________ gradient

2 Factors Affecting the Speed of Diffusion

Lighter molecules diffuse

________________ faster

than heavier molecules.

Relative molecular

________________ mass

affects the speed of diffusion.

Diffusion happens more quickly at

________________ warmer

temperatures than at cooler temperatures.

3 Diffusion in Gases

Gas particles move in

________________ random

motion and collide with each other.

Diffusion in gases is

________________ fast

because particles move rapidly and freely.

Ethylamine diffuses faster than HBr because it has a lower relative molecular

________________ mass

Kinetic Theory Explanation

In gases, forces of attraction are

________________ negligible

, so particles spread out quickly.

4 Diffusion in Liquids

Particles in liquids are free to

________________ move

and collide, so diffusion can occur.

Diffusion in liquids is

________________ slower

than in gases.

This is because there are weak forces of

________________ attraction

between particles.

When a liquid can be smelt far away, it has first

________________ evaporated

and then diffused through the air.

5 Diffusion in Different States of Matter

Diffusion is fastest in

________________ gases

Diffusion is slower in

________________ liquids

Diffusion does not occur in

________________ solids

because particles are tightly packed and only vibrate in fixed positions.

6 Miscellaneous Points

Diffusion can occur in

________________ miscible

liquids.

Diffusion is also possible for solids that

________________ dissolve

in liquids.

At the same temperature, lighter molecules diffuse faster than

________________ heavier

molecules.

You need to know:

(a) Diffusion is the random movement of particles from a region of high concentration to a region of low concentration.

(b) Diffusion occurs down a concentration gradient.

(c) Diffusion is fastest in gases and slower in liquids.

(d) Lighter particles diffuse faster than heavier particles at the same temperature.

(e) Diffusion in solids does not occur because particles only vibrate about fixed positions.

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