Diffusion Edexcel International GCSE Science (Single Award) revision
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In plain words
Spray air freshener in one corner and the smell slowly reaches the whole room. Particles move about at random, and that alone spreads them from where there are many to where there are few. That is diffusion, and it's how oxygen gets into your blood and into every cell.
Three things to know
- Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient, as a result of their random movement.
- It needs no energy from the cell: the energy is the kinetic energy of the moving particles.
- Diffusion is faster with a bigger concentration gradient, a higher temperature, a larger surface area and a shorter distance.
Tips and tricks
- "Net movement", "higher to lower concentration" and "random movement" are the three phrases that earn the marks.
- Exchange surfaces (alveoli, villi, root hairs) are all thin with a large surface area. Both speed up diffusion.
It lands in your notebook with its questions as flashcards.
Diffusion: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
In which direction do particles move by diffusion?
They spread out down the concentration gradient.
Where does the energy for diffusion come from?
Diffusion is passive: the cell doesn't supply energy.
Which change makes diffusion faster?
A steeper gradient means a faster net movement.
Which gas diffuses out of the blood into the alveoli?
Its concentration is higher in the blood than in the air.
Why do exchange surfaces have a large surface area?
More particles can cross at once.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
Diffusion
Edexcel International GCSE Science (Single Award) 4SS0 · 7 marks · papermunch.org
Name ______________________________ Date ______________
State what is meant by diffusion.[2]
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The net movement of particles from a region of higher concentration to a region of lower concentration, as a result of their random movement.
State three factors that increase the rate of diffusion.[3]
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Any three: a larger concentration gradient, a higher temperature, a larger surface area, a shorter distance.
Explain why oxygen diffuses from the air in the lungs into the blood.[2]
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The concentration of oxygen is higher in the air in the alveoli than in the blood, so there is a net movement down the concentration gradient.
Answers: Diffusion
- 1. The net movement of particles from a region of higher concentration to a region of lower concentration, as a result of their random movement.
- 2. Any three: a larger concentration gradient, a higher temperature, a larger surface area, a shorter distance.
- 3. The concentration of oxygen is higher in the air in the alveoli than in the blood, so there is a net movement down the concentration gradient.