1. Diffusion and Osmosis

2. Diffusion
The net movement of atoms or molecules from a region where they are at a higher concentration to a region where they are at a lower concentration is called diffusion.
Concentration refers to the number of particles per unit volume.

3. Diffusion Process
Diffusion continues until the particles are uniformly distributed throughout the system.
When this happens, net movement of particles is zero and the equilibrium of the system is reached. At this point, diffusion has stopped.

4. Movement of Particles in Diffusion
Diffusion occurs spontaneously and does not involve any energy taken in or given out, i.e. there is no gain or loss of energy.
The movement of particles during diffusion is random, with each moving in a different direction.

5. Diffusion - Illustrated

6. Diffusion of Bromine Gas

7. Critical Thinking
Which state of matter (solids, liquids or gases) will diffusion happens the fastest? Why?
Hint: Think about movement of the particles in each state of matter. Which particles can move the fastest?

8. Osmosis
Watch video:

9. Osmosis
Osmosis is the net movement of water molecules from a region of their higher concentration to a region of their lower concentration through a partially permeable membrane.

10. Osmosis
Given two solutions of the same volume, the solution with more solute particles implies higher concentration of solute but lower concentration of water
Rationale: Particles take up space. To have more solute particles in the same amount of space (volume), there must be less water molecules.

11. Osmosis
Osmosis through the partially permeable membrane will continue until the water concentration is uniformly distributed between the 2 solutions.
Osmosis stops when the 2 solutions are of equal water concentration.

12. Diffusion vs Osmosis Osmosis is just a special kind of diffusion.
In osmosis, water molecules diffuse through a partially permeable membrane.
On the other hand, diffusion generally involves any type of molecules and a partially permeable membrane need or need not be present.

13. Types of Solutions Isotonic solution:
“iso” means equal. Isotonic solutions have equal water concentration.
Hypotonic solution:
Solution has higher concentration of water (lower concentration of solute) than the other solution.
Hypertonic solution:
Solution has lower concentration of water (higher concentration of solute) than the other solution.

15. Animation on Osmosis

16. Osmosis and Living Things (Look at notes)

17. Recap…
In which organ in our body does the exchange of oxygen and carbon dioxide between our body and the surrounding air take place?

19. Effect of different types of solutions on living cells
Animal Cell in Hypotonic solution (eg. pure water)
Higher water concentration in extracellular solution than intracellular solution
Water enters animal cell via osmosis and it swells.
Net gain of water from extracellular solution into the cell.
If a large amount of water enters the cell, it will burst and release contents of the cell.

20. Effect of different types of solutions on living cells
2) Animal Cell in Hypertonic solution (eg. salt solution)
Lower water concentration in extracellular solution than intracellular solution
Water exits animal cell via osmosis and it shrinks.
Net loss of water from cell into extracellular solution.
If a large amount of water exits the cell, it will become shriveled.

21. Effect of different types of solutions on living cells
3) Animal Cell in Isotonic solution
Equal water concentration in extracellular solution and intracellular solution
No net gain or loss of water.
Animal cell prefers to be in isotonic solution.

22. Effect of different types of solutions on living cells
Plant Cell in solution with higher water concentration (eg. pure water)
Higher water concentration in extracellular solution than intracellular solution
Net gain of water from extracellular solution into the cell.
Central vacuole increases in size and plant cell start to swells.
Plant cells do not burst due to its cell wall.
When the cell wall is stretched to its maximum, the plant cell cannot take in any more water and are said to be turgid.
Plant cell prefers to be in hypotonic solution.

23. Effect of different types of solutions on living cells
2) Plant Cell in solution with lower water concentration (eg. salt solution)
Lower water concentration in extracellular solution than intracellular solution
Net loss of water from cell into extracellular solution.
Central vacuole decreases in size before the cell membrane start to pull away from the cell wall.
This leaves a visible gap between cell wall and cell membrane. This process is called plasmolysis.
Plants with plasmolyzed cells will wilt.

24. Effect of different types of solutions on living cells
3)Plant Cell in solution with same water concentration
Equal water concentration in extracellular solution and intracellular solution
No net gain or loss of water.
Cell appearance is described as flaccid.

25. Possible ACE Assignments
Critical Thinking Qn 3
Processes of Reverse Osmosis and Desalination