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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.
1Definition 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
.
2Factors 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.
3Diffusion 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.
4Diffusion 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.
5Diffusion 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.
6Miscellaneous 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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