Name: ______Date: ______Period: ______

POTATO OSMOSIS (DIFFUSION OF WATER) LAB

1. Cells —> tissues —>organs —> organ systems —> organism

2. All living things need and use the universal solvent called ______

3. The ______dissolves the ______to make the ______.

4.  Osmosis is the diffusion of ______across a ______from areas of ______water concentration to areas of ______water concentration .

5.  Molecules of any substance passively move ______a gradient.

List the 8 ways of collecting data and circle the methods we will be using today:

1.  ______

2.  ______

3.  ______

4.  ______

5.  ______

6.  ______

7.  ______

8.  ______

Objective Part I

Using potato tissue and various solutions containing different amounts of solutes, I will measure mass changes to demonstrate which solutions are Hypotonic, which are Hypertonic and which are isotonic to the potato tissue.

EXPERIMENT : You will be setting up 3 sample solutions with 2 slices of potato in each sample.

For each of the setups of A , B & C, you will:

1.  Fill cup ½ way with the solution

2.  Find the initial masses for the slices of potato and record qualitative and quantitative data in the data table provided.

3.  Separate the slices from each other and drop them into the solution to soak for a minimum of 30 minutes

4.  After soaking, remove slices, carefully wipe off excess water and mass them again (DO NOT squeeze the water out of the potatoes when drying)

5.  Record qualitative and quantitative data for final masses

6.  Pour remaining solution down the sink, rinse the cups and throw away potato slices in the garbage.

7.  Rinse & dry cups and return them to your teacher.

8.  Calculate the percentage of mass change for each of the samples in your group.

9.  Plot your groups data points on the graph provided

10. Draw a line of best fit

11. Answer the analysis questions.

Formulate your Hypotheses:

A.  If the tissue is in a HYPOtonic solution, the cells will ( increase / stay the same / decrease ) in mass because the water concentration is ( higher / equal / lower ) in the solution than the cell.

B.  If the tissue is in a ISOtonic solution, the tissue will ( increase / stay the same / decrease ) in mass because the water concentration is ( higher / equal / lower ) in the solution and the cell.

C.  If the tissue is in a HYPERtonic solution, the cells will ( increase / stay the same / decrease ) in mass because the water concentration is ( higher / equal / lower ) in the solution than the cell. .

Set-up / Qualitative
Before (what does it look like?) / Qualitative
After
(what does it look like?) / Beginning
Mass / Ending
Mass / Mass
Difference / %
Change
In Mass
A
B
C

Title:______


Lab Questions for Part I

1.  How do you describe the concentration of water and solutes in a hypotonic solution?

2.  How did the hypotonic solution affect the tissue in the lab?

3.  Which way did water diffuse when tissue was placed into the hypotonic solution?
(into or out of cells) Why?

4.  How do you describe the concentration of water and solutes in a hypertonic solution?

5.  How did the hypertonic solution affect the tissue in the lab?

6.  Which way did water diffuse when tissue was placed into the hypertonic solution?
(into or out of cells) Why?

7.  What happened to the turgor pressure (pressure within the cell) when placed into the hypertonic solution?

8.  How do you think the cell walls may have been affected in the hypertonic solution?

9.  Will the cells in the hypertonic solution ever be able to achieve homeostasis? Explain.

10. Is the water moving in and out of the cells passively or actively?

11. Explain why none of the potato samples will ever experience cytolysis (bursting)?

12. Explain which of the samples; A, B or C is closest to being an isotonic environment?

13. What process was demonstrated in this lab?