Potato in Solutions Activity

Assignment

On a separate sheet of paper record the title, question, your hypotheses, your data and your responses to the analysis questions.

Question:

Record on your paper: What are the effects on a potato core's mass and dimensions when placed in two different concentrations of salt water?

Background:

Refer to your notes and textbook.

Hypotheses (predictions):

Record your predictions on your paper. Note there are two solutions so there will be two predictions.

Equipment:

(2) potato cores	(2) test tubes	(1) balance	test tube rack
tape, marker & ruler	fresh water	table salt	graduated cylinder

Procedure:

1. Make 25 ml of a 3% salt water solution. Record the amount of salt you used here : ______________
2. Measure the dimensions and mass of the potato cores. Each core will be different.
3. Place a potato core in each of the test tubes. Label the test tubes.
4. Pour sufficient fresh water in the first test tube to cover the core with 2cm of water.
5. Pour sufficient 3% solution in the second test tube to cover the core with 2cm of solution.
6. The next day, measure the dimensions and mass of the potato cores.

Data Section:

1. Record the before and after length, diameter, volume and mass of each core.
2. Record the percentage change for each measurement. Use this formula:

   [(ending measurement - starting measurement) / starting measurement]* 100

3. Be sure to show all calculations!

Analysis:

Answer these analysis questions in complete sentences.

1. For each solution did the potato core grow, shrink or stay the same?
2. Why would the potato core change size?
3. Make a before sketch of a typical plant cell and two after sketches: one for the fresh water core and one for the salt water core.
4. Describe the two solutions in terms of being hypotonic, hypertonic and isotonic solutions.
5. Graph the percentage potato core mass change vs. solution concentration.
6. Looking at your graph, estimate what salt concentration would be an isotonic solution for the potato core ? Hint: what would a 0% mass change mean?