1. No category

Osmosis
The diffusion of water molecules
across a partially permeable
membrane
Why do cells need water?
Objectives by the end of this lesson
• Describe osmosis
• Explain how a model cell can gain or lose
water by osmosis
• Set up practical apparatus effectively to
demonstrate osmosis
Osmosis
• Osmosis is the diffusion of water molecules across a
partially permeable membrane.
• What does partially permeable mean?
•
• What is diffusion?
• What affects the rate of diffusion?
Experiment to show osmosis
This is left set up .What
happens to the level of
sucrose solution in the
capillary tube?
Water
Explanation of results
1. Why does the sucrose solution move up the
tube.
2. Where are there a lot of water molecules?
3. Where are there fewer water molecules?
4. In which direction do the water molecules
move?
Osmosis- Check your understanding
• What will happen to a red blood cell if it is
placed in a very dilute solution?
• Explain your answer
• What will happen to a red blood cell placed in
a very concentrated solution?
• Explain your answer