New
New
Year 7

Diffusion through a selectively-permeable membrane: practical

I can explain observations of diffusion through a selectively-permeable membrane.

New
New
Year 7

Diffusion through a selectively-permeable membrane: practical

I can explain observations of diffusion through a selectively-permeable membrane.

Lesson details

Key learning points

  1. Particles of some substances are small enough to diffuse through holes in a selectively-permeable membrane.
  2. Particles of these substances move through the selectively-permeable membrane in both directions.
  3. Predict the direction of net movement of particles through a selectively-permeable membrane.
  4. Observe the direction of net movement of a substance through a selectively-permeable membrane (e.g. Visking tubing).
  5. Explain observations of the diffusion of a substance through a selectively-permeable membrane.

Common misconception

Particles only move through a selectively-permeable membrane in one direction.

The lesson explores the idea that particles move through a selectively-permeable membrane in both directions, but that net movement is down a concentration gradient.

Keywords

  • Selectively-permeable membrane - A membrane is selectively-permeable if some substances can move through it but others cannot.

  • Particles - All substances are made up of particles that are too small for us to see.

  • Diffusion - Diffusion is the net movement of particles of a substance down a concentration gradient.

  • Concentration gradient - A concentration gradient is a difference in the concentration of particles from one area to another.

  • Net movement - Net movement is the overall movement of particles from one area to another.

A video demonstration is provided, but the experiment could also be done as a teacher demonstration with use of a visualiser so everybody in the class can observe what happens. Use pre-soaked Visking tubing.
Teacher tip

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What is the name of the structure labelled A in the diagram of an animal cell?
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Correct answer: cell membrane
cell wall
cytoplasm
nucleus
Q2.
What is the job of the cell membrane in an animal cell?
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Correct answer: It controls what can enter and leave the cell.
It is a fluid that fills the cell.
It is where photosynthesis takes place.
It stores the cell’s DNA.
Q3.
The cell membrane has lots of small in it.
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Correct Answer: holes, gaps, pores
Q4.
Who correctly explains how the particles of oxygen got into the cell?
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Jacob: “The cell breathed the oxygen particles in.”
Correct answer: Aisha: “The particles diffused through the cell membrane.”
Lucas: “The cell sucked them in from the blood.”
Sofia: “The cell is fully permeable to all particles, including oxygen.”
Q5.
Particles of carbon dioxide …
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Correct answer: can move through the cell membrane in both directions.
cannot move through the cell membrane.
will only move through the membrane from inside the cell to outside the cell.
will only move through the membrane from outside the cell to inside the cell.
Q6.
The movement of carbon dioxide particles will be from inside to outside.
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Correct Answer: net, overall, greatest, largest, biggest
Q1 UYSEG

6 Questions

Q1.
Particles of iodine can only move through holes in the membrane because they are ...
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concentrated.
heated.
large.
Correct answer: small.
Q2.
Particles of starch are too to move though holes in the membrane.
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Correct Answer: large, big
Q3.
Particles of iodine move through the membrane into the tubing due to diffusion down a gradient.
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Correct answer: concentration
diffusion
movement
net
Q4.
Because particles of iodine can move through the membrane but particles of starch cannot, the membrane is described as -permeable.
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Correct Answer: selectively, partially, semi
Q5.
The diagram shows the experiment at the start. Who correctly predicts what the liquid inside the tubing will look like after 10 minutes?
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Alex: “It will be yellow or pale brown.”
Andeep: “It will still be colourless.”
Correct answer: Sofia: “It will be blue/black.”
Q6.
The diagram shows the experiment after 10 minutes. Match each observation to the correct explanation for it.
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Correct Answer:liquid inside the tubing is blue/black,starch and iodine are both present

starch and iodine are both present

Correct Answer:liquid outside the tubing is pale brown,only iodine is present, no starch

only iodine is present, no starch

Correct Answer:full colour change took a few minutes,iodine diffused into the tubing from the edges to the middle

iodine diffused into the tubing from the edges to the middle