1. Exchange of materials p.214
Osmosis
Exchange of materials
p.214

2. Requirements 24 boiling tubes 12 cork borer 12 tiles 12 pens 12 racks
Cling film
Potatoes
Demo osmometer
No worksheets

3. Objectives Students should learn:
that water often moves across boundaries by osmosis and why it is important
that osmosis is the diffusion of water through a partially-permeable membrane from a dilute to a more concentrated solution
that differences in concentrations of solutes inside and outside cells cause water to move by osmosis.

4. Outcomes Most students should be able to: define osmosis
distinguish between diffusion and osmosis
carry out an experiment to find out about the process of osmosis
explain the results of experiments in terms of osmotic movement of water.
Some students should also be able to:
explain the importance of osmosis in plants and animals.

5. Specification
Dissolved substances move by diffusion and by active transport. [B3.1.1 a)]
Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules. [B3.1.1 b)]
Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis. [B3.1.1 c)]
Controlled Assessment: B4.5 Analyse and interpret primary and secondary data. [B4.5.4 a)]

6. Workbook
P.101-2

7. Which way does the flow go?
Aims
In this activity you will think about the flow of money. This can help you to understand osmosis.
Task
Imagine that there are three friends, all of whom have overdrafts at the bank. They meet up and compare their finances. They decide that whoever is the most overdrawn should get money from anyone who is less in debt than they are. This means that money will move from an account where there is more money, to an account where there is less money.

10. In the same way, water will move across a partially permeable membrane from where there is more water to where there is less water. This is called osmosis. On the diagram below, draw an arrow to show the direction in which the water will move.

11. In the same way, water will move across a partially permeable membrane from where there is more water to where there is less water. This is called osmosis. On the diagram below, draw an arrow to show the direction in which the water will move.

12. define osmosis
osmosis is the … of water through a … membrane from a … to a … solution
Missing words
partially-permeable, more concentrated, dilute, diffusion

13. define osmosis
osmosis is the diffusion of water through a partially permeable membrane from a dilute to a more concentrated solution
Missing words
partially-permeable, more concentrated, dilute, diffusion

14. comparing diffusion and osmosis

15. Comparing osmosis and diffusion
Movement of any very small particle
From a high to low concentration
Doesn’t have to pass through a barrier
Kinetic energy from particles
Osmosis
Movement of water molecules only
From a dilute to a concentrated solution
Passes through a partially permeable membrane
Kinetic energy from particles

16. experiment to find out about the process of osmosis

17. Partially permeable
(more concentrated solution)
(dilute solution)

18. explain the results of experiments in terms of osmotic movement of water.

19. The osmometer
The water is a ……. Solution, the sugar solution is more ………..
The visking tubing is a membrane
Water moves into the visking tubing by
The bag fills out and the contents press out on the walls. The bag is firm or
Water continues to move into the bag, The pressure created forces the liquid up the capillary tube.

20. The osmometer
The water is a dilute Solution, the sugar solution is more concentrated solution
The visking tubing is a partially permeable membrane
Water moves into the visking tubing by osmosis
The bag fills out and the contents press out on the walls. The bag is firm or turgid
Water continues to move into the bag, The pressure created forces the liquid up the capillary tube.

21. explain the importance of osmosis in plants and animals.
Read p.215

22. The effect of osmosis on animal and plant cells
Animal cells
In a concentrated solution lose water by osmosis and shrink
In a dilute solution take in water by osmosis and burst as the cell membrane is weak
Plant cells
In a concentrated solution the cytoplasm and cell membrane shrink away from the cell wall = plasmolysed cell/flaccid
In a dilute solution take in water and the cytoplasm pushes out on the cell wall = turgid/firm cell
Plasmolysis video lettuce video

23. Slugmosis video Make a script for the video using these words Osmosis
Partially permeable
Diffusion of water molecules
Dilute solution
More concentrated solution

24. Osmosis in potato tissue
Have you ever wondered why they store the cut chips in slightly salty water in the chip shop before they fry?

25. Method Each group will need: 2 x boiling tubes 1 x tube rack
1 x marker pen (?)
2 x potato chips (fair testing???)
1 x 20 cm3 syringe (for?)
Some Cling film (?)
Repeats / reliability (?)
1.0 M
SCC
0.0 M
DBB
Draw a blank results table (?)
Label the boiling tubes with the treatment and your initials.
Using the syringe, add 20 cm3 of the sugar solution to each tube.
Cut the potato chips to exactly 30 mm.
Record initial length in mm on your results table.
Put the chips into the boiling tubes (one per tube) and cover with cling film.
Place tubes into your group’s tube rack and put carefully onto the side bench.

26. Table of results for osmosis in potato chips
Tube
Length of chip
Before expt /mm
Length of chip after expt
/mm
Change in length
Percentage change in length A B
Formula for percentage change = change/original x100