Diffusion and Osmosis Worksheet, Page 1 of 3, 1/12/12

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Diffusion and Osmosis Worksheet Answers

1. Write the definition of diffusion from memory. If you can’t, refer to the vocabulary sheet and practice until you can.

The movement of particles in solution from areas of high concentration to areas of low concentration.

2. A membrane that allows all molecules in the solution to pass through is called what type of membrane?

Permeable.

3. A membrane that allows some molecules in the solution, but not others, to pass through is called what type of membrane?

Selectively permeable (or semi-permeable).

4. A membrane that does not allow any molecules in the solution to pass through is called what type of membrane?

Impermeable.

5. Look at the diagram below. Describe what will happen over time. Sketch the situation at a much later time after equilibrium has been reached.

The large dots (molecules) inside the cell will diffuse out of the cell. The small dots (molecules) will diffuse into the cell. At equilibrium there will be an equal concentration of large dots inside the cell as out. There will be an equal concentration of small dots inside the cell as out.

Diffusion and Osmosis Worksheet, Page 2 of 3, 1/12/12

6. Consider the container below which has two separate compartments separated by a

permeable membrane. Describe what will happen over time. Sketch the situation at a much later time. What will be the concentrations of salt and sugar on each half of the container?

Salt will move from A to B. Sugar will move from B to A. Eventually there will be 15% salt in either side and 2% water in either side.

7. What is the percentage of water in each half at the beginning? 70% water on the left. 96% sugar on the right.

8. What is the percentage of water in each half at the end? 83% water on both sides.

9. Did the water move across the membrane? Which direction. Yes. It went from B to A. The water level in A went up and in B went down.

10. Write down the definition of osmosis from memory. If you can’t, refer to the vocabulary sheet and practice until you can.

The diffusion of water through a membrane.

Diffusion and Osmosis Worksheet, Page 3 of 3, 1/12/12

11. Consider the drawing. What will happen over time?

Water will enter the cell through the process of osmosis. It will eventually burst.

12. Consider the drawing. The membrane is permeable to salt and water, but not to sugar. a. What is this type of membrane called? b. In what direction will the salt move? c. In what direction with the sugar move? d. In what direction will the water move? e. In which compartment will the water rise?

a. Selectively permeable. b. Salt will move from B to A. c. The sugar will not move because the membrane is not permeable to sugar. d. There is 90% water in A at the beginning. There is 80% water in B at the beginning.

Thus, the water will move from A to B. e. The water in level B will rise.

This activity is modified from Biology as Scientific Inquiry, Unit II, Cells and Cell Processes, © 2010, Connection Point and Ron Thompson.