1. Task 1 - what’s the solution?
Osmosis
Task 1 - what’s the solution?
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
definition
definition
definition
the liquid into which the solute is poured and dissolved
substance that is dissolved in a solvent
is made when a solute is dissolved in a solvent
example
e.g. salt and sucrose
example
e.g. water and ethanol
example
e.g. salty water ©
23698

2. Osmosis Task 2 – plants and water Look at the two pictures.
Describe the differences.
Can you explain the differences? ©
23698

3. Osmosis Task 3 – model cell experiment Instructions
Make two model cells by filling two lengths of Visking tubing (tie a knot in one end) with a dilute (weak) salt solution.
Put one model cell into a boiling tube containing distilled water.
Put the other model cell into another boiling tube containing a concentrated (strong) salt solution.
Leave for 10 minutes.
dilute salt solution
dilute salt solution
distilled water
concentrated salt solution
Predict what you think will happen.
After 10 minutes look at the model cells and describe their appearance.
Explain what has happened and why. ©
23698

4. net movement of water molecules
Osmosis
Task 4 – membranes and solutions
water
membrane
sugar solution
net movement of water molecules
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. ©
23698

5. partially permeable membrane
Osmosis
Task 5 – partially permeable membranes
What does partially mean?
In part, not totally, slightly etc
What does permeable mean?
Allows liquids or gases to pass through it
What is meant by a partially permeable membrane?
A membrane that lets small molecules through but not large molecules
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…
…but large particles cannot.
partially permeable membrane ©
23698

6. Osmosis Task 6 – what is 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. ©
23698

7. Osmosis Task 7 – osmosis and blood cells 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. A C B
Image source: ©
23698

8. Osmosis Going further sugar solution water net movement
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. ©
23698

9. Osmosis Because there are more freely moving water molecules on
net movement
Sugar molecules can pass through the membrane but, being surrounded by a cloud of water molecules, they move more slowly.
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. ©
23698

10. Osmosis Task 8 – osmosis animation
Design and make your own video to explain osmosis. ©
23698

11. 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. ©
23698