If the salt water solution is hypertonic it would contain a higher concentration of solute and a lower concentration of water than the blood cells. Fluid would flow from the area of low solute concentration (the blood cells) to an area of high solute concentration (water solution). As a result the blood cells will shrink.

If the salt water solution is isotonic it would contain the same concentration of solute as the blood cells. Fluid would flow equally between the blood cells and the water solution. As a result the blood cells will remain the same size.

If the salt water solution is hypotonic it would contain a lower concentration of solute and a higher concentration of water than the blood cells. Fluid would flow from the area of low solute concentration (water solution) to an area of high solute concentration (the blood cells). As a result the blood cells will swell and even burst.

How Do Cells Take in Water and Other Substances?

• Matter is made up of small, discrete molecules/ particles in constant random motion
• Molecules are dispersed in a random direction.
• Tend to spread from an area where they are more concentrated to an area where they are less concentrated.
• This dispersion continues until the concentration of molecules is the same everywhere - evenly distributed (EQUILIBRIUM).
• This process is called DIFFUSION

Learners' Outcomes

1. Define the process of diffusion as the net movement of molecules from a region of high concentration to a region of low concentration.
2. Define the process of osmosis as the net movement of water molecules from a region of higher water potential, to a region of lower potential across a selectively permeable membrane.
3. Explain that osmosis is a subset of diffusion and that osmosis is restricted to the net movement of water molecules whilst diffusion involves the movement of any type of molecules. In addition, be aware that a selectively permeable membrane is involved in osmosis whilst a membrane need not necessarily be present for diffusion.
4. Explain how animal and plant cells behave differently in solutions of varying water potential.
5. Appreciate the importance of diffusion and osmosis to living systems and list examples of both processes.

List the factors that affect diffusion...
1. Size of driving force
2. Membrane surface area
3. Membrane permeability

Describe the movement of molecules with respect to concentration gradient...
When molecules are moving from the region of higher concentration to the region of lower concentration, it is called going down their concentration gradient. On the other hand, when molecules are moving from the region of lower concentration to the region of higher concentration, it is called going up their concentration gradient which basically means going against its concentration gradient.

Define diffusion...
Diffusion is the spontaneous net movement of molecules moving from a region of higher concentration to a region of lower concentration.

What is concentration gradient?
I think concentration gradient is present when molecules are not evenly distributed and it kinds of forces the molecules in the region with higher concentration to go to the region with lower concentration.

What is diffusion?
Diffusion is a process whereby molecules move from areas of their higher concentration to areas of their lower concentration.

When will it stop?
It will stop when all the molecules are evenly dispersed.

Do molecules even stop moving?
Molecules never stop moving. They are always moving because of their kinetic energy.

What are the factors that determine the rate of diffusion?
Temperature, size of molecules and the steepness of the concentration gradient.

Can you name some examples of diffusion in a living organism?
1. Diffusion takes place when animals breathe in oxygen and that oxygen is distributed to all cells in that animal. Carbon dioxide in turn is also diffused from the cells into the lungs to be breathed out.

2. Diffusion takes place when a plant takes in carbon dioxide and gives out oxygen during photosynthesis.

These are the procedures of a very fun experiment I conducted in class.

	Procedures
1.	Fold the paper towel into two to make it a 2-ply piece of paper.
2.	Cut it into 3 strips of about 30x20mm and briefly soak them in the cabbage juice.
3.	Remove immediately once the paper turns light purple.
4.	Spread them open and leave aside to dry on the white tile.
5.	Cut your agar block to the following specifications: a.     3 pieces of 5x5x5mm b.     1 piece of 5x5x20mm c.      1 piece of 10x10x10mm
6.	Label your petri dish accordingly based on the solutions that are assigned to you.
7.	Immerse ONE piece of agar of size 5x5x5mm, 5x5x20mm and 10x10x10mmi in lemon juice or baking powder solution.
8.	Record the time it takes for each of the agar to turn uniformly into a different colour in table 1 below.
9.	Immerse the 2 other pieces of 5x5x5mm agar into each of the 2 remaining liquids.
10.	Observe the colour change and record the results in table 2.
11.	Introduce a few drops of each of your 3 solutions onto a different strip of the cabbage juice soaked 2-ply paper towel.
12.	Observe the colour change and record the results in table 2.
13.	Transfer 2cm3 of each of the solution into separate test tubes.
14.	Label the test tube accordingly.
15.	Add an equal volume of cabbage juice to each of these test tubes and record the colour change in table 2. (2cm3 is approximately 2cm in height)