# osmosis challenge lab

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```							Name ______________________________________                               Period _______

OSMOSIS CHALLENGE

You will now be given the opportunity to apply the principles you learned in the previous exercises.

Question: What is the actual molarity of a potato cell?

Guidelines:
You have the following materials to use:
potatoes
beakers
sucrose solutions at the following concentrations:
0.2, 0.4, 0.6, 0.8 and 1.0M.
scale
aluminum foil
a graph for your final results (in % change in mass)

In order for the class to have similar data to compare use the following:
4 potato cylinders per solution, cut using the cork borer.
All 5 sucrose solutions
Limit the amount of solution to 100ml per beaker (so I don’t have to make so much).

Pre – Lab
(This will be your ‘entry ticket’ to the lab).

With your partners (3 per group), design an experiment that will demonstrate the actual molarity (concentration of
sucrose) in a potato cell.

Your experiment must include:
1. A detailed procedure that can be followed without any explanation on your part.
(Neatly written to be put in your lab notebook unchanged).
2. Identification of the manipulated, responding and controlled variables.
3. A control group.
4. A data table.

Post lab
Data Section
1. Completed data table.
2. Completed graph.

Analysis Section (presented in a logical order of your choice)
1. Explanation of the data in the table. (Cite at least 3 data points).
2. Explanation of the graph. (Cite at least 3 data points).
3. Possible sources of error /inaccuracy. (Necessary only if there is data that you are uncomfortable with
or seems inaccurate).

Conclusion Section:
1. Answer to the question: “What it the actual molarity of a potato cell?”
2. Describe how you could improve on your lab.
3. Other areas of investigation or questions to be answered from this lab.

Summary questions
Summary Questions

1. Based on your observations in the lab:

a. The mass of cells in a hypotonic solution will _____________________ (increase/decrease/stay constant)

because _____________________________________________________________.

b. The mass of cells in a hypertonic solution will _____________________ (increase/decrease/stay constant)

because _____________________________________________________________.

c. The mass of cells in a isotonic solution will _____________________ (increase/decrease/stay constant)

because _____________________________________________________________.

Salt movement into and out of cells is similar to that of sucrose. Knowing that, answer the following questions:

2. In the winter, icy roads are often salted to remove the ice and make them less slippery. Grasses and other
plants often die near the side of these roads. What causes this to happen?

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

3. When a person is given fluid intravenously (an I.V.) in the hospital, the fluid is typically a saline (salt) solution
isotonic to human body tissues. Explain why this is necessary.

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

4. What if the unthinkable happened at the hospital! A patient was given an I.V. bag with distilled water in it rather
than saline solution. Describe what would happen to their red blood cells and explain why this would occur.

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

5. Many freshwater one-celled organisms, like Paramecium, have contractile vacuoles. These structures collect and
pump out excess water that accumulates in the cell. Explain why these organisms needs such a structure.
_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________
6. Explain why contractile vacuoles would be of little value to one-celled organisms living in salt water.

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

7. Popcorn sold at movie theaters is very salty, causing people to become thirsty and to buy soft drinks. Explain
why salty popcorn causes this thirst.

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

8. Explain why soft-bodied invertebrates, like slugs, die when you pour salt on them.
_________________________________________________________________________________________

_________________________________________________________________________________________

_________________________________________________________________________________________

9. In each case, label the diagrams as to whether the red blood cells are in a hypertonic, isotonic, or hypotonic
solution.

```
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