Diffusion and osmosis
Particles move from high to low concentration; osmosis is water doing this across a membrane.
The common mistake
Saying water moves toward the more dilute solution in osmosis.
Instead: Water moves from where there's more water (dilute) to less water (concentrated) through a partially permeable membrane.
Worked example with Guide me
A potato slice is placed in very salty water. What happens?
- Sugar · Where is there more water — inside the potato or the salt water?Student · Inside the potato.
- Sugar · So which way does water move?Student · Out of the potato.
Answer: It loses water and gets smaller and floppy.
Try 3 practice questions
1. Does diffusion need energy?
Show answer
No — it's passive
2. A red blood cell in pure water will…?
Show answer
Swell and may burst
3. Moving particles against a gradient is called…?
Show answer
Active transport
Quick answers
- What is the most common mistake with diffusion and osmosis?
- Saying water moves toward the more dilute solution in osmosis.
- How do I get diffusion and osmosis right?
- Water moves from where there's more water (dilute) to less water (concentrated) through a partially permeable membrane.
- Can you show a worked example?
- A potato slice is placed in very salty water. What happens? It loses water and gets smaller and floppy.
Related concepts
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