Task 1 - what’s the solution?
Osmosis
Can you define what each of the following are and give an
example? Click on the boxes to reveal the answers.
a solute
a solvent
a solution
substance that
isdefinition
dissolved in
a solvent
the liquid into
which the solute
isdefinition
poured and
dissolved
is made when a
solute
is dissolved
definition
in a solvent
e.g. salt and
example
sucrose
e.g. water
example
and ethanol
e.g.example
salty water
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Task 2 – plants and water
Osmosis
Look at the two pictures.
Describe the differences.
Can you explain the differences?
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Task 3 – model cell experiment
Osmosis
Instructions
1. Make two model cells by filling two lengths of Visking tubing (tie a knot in
one end) with a dilute (weak) salt solution.
2. Put one model cell into a boiling tube containing distilled water.
3. Put the other model cell into another boiling tube containing a
concentrated (strong) salt solution.
4. Leave for 10 minutes.
dilute salt solution
dilute salt solution
distilled water
concentrated salt solution
5. Predict what you think will happen.
6. After 10 minutes look at the model cells and describe their appearance.
7. Explain what has happened and why.
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Osmosis
Task 4 – membranes and solutions
water
membrane
sugar solution
net movement of water molecules
1.
2.
3.
4.
5.
What can you say about the movement of the water and sugar molecules
in a solution?
Which particles can move through the membrane and why?
Will the water molecules move both ways through the membrane?
Which side has the highest concentration of water molecules?
What will be the overall movement of water molecules? Click on the
correct arrow.
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Task 5 – partially permeable membranes
Osmosis
1. What does partially mean?
In part, not totally, slightly etc
2. What does permeable mean?
Allows liquids or gases to pass through it
3. What is meant by a partially permeable membrane?
A membrane that lets small molecules through but not large
molecules
4. Draw a diagram to show how a partially permeable membrane would
allow water molecules through but not glucose molecules.
Generally, small
particles can pass
through…
partially
permeable
membrane
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…but large
particles
cannot.
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Task 6 – what is osmosis?
Osmosis
Copy out and complete the definition of osmosis.
Click each box to reveal the answer.
Osmosis is a special type of diffusion.
Osmosis is the diffusion of water molecules …
… from a region of high concentration of water molecules …
… to a region of low concentration of water molecules …
… across a partially permeable membrane.
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Task 7 – osmosis and blood cells
Osmosis
Look at the three pictures.
Describe the appearance of the red blood cells in each.
What do you think has caused the differences in the cells?
Make a poster to explain the role of osmosis in pictures B and C.
Make sure that you include one deliberate mistake on your poster.
C
A
B
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Osmosis
Going further
water
net movement
sugar solution
There are as many water molecules on the right as there are on the left. What
will be the net movement of water molecules by osmosis?
Look at the diagram to see if you can explain why.
Several of the water molecules are momentarily attracted to the sugar
molecules and are not free to move.
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net movement
Osmosis
Because there are more freely moving water molecules on
the left, more diffuse through the pores of the membrane
from left to right than from right to left.
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Task 8 – osmosis animation
Osmosis
Design and make your own video to explain osmosis.
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Osmosis
Teaching notes
Task 3 - model cell
The model cell makes a great starting point to stimulate discussion about movement of
molecules in and out of cells.
Equipment needed per group:
• 2 x boiling tubes and stand
• 2 x 15 cm lengths of Visking tubing
• cotton thread
• distilled water
• concentrated sugar or salt solution
• dilute sugar or salt solution
Task 7
Students are asked to leave one deliberate mistake on their poster.
When completed the posters are swapped with another group. Students then try to identify
mistakes on the poster.
Task 8
The students will need access to tablets to be able to make a video or animation of osmosis.
Modelling dough would be ideal to use. As an alternative students could write and give a
short presentation to the rest of the class.
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