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# Potato in Solutions Activity (mass)

## Questions:

- What is the mass change of a potato cube in fresh water?
- What is the mass change of a potato cube in salt water?

## Hypotheses (predictions):

(Record your predictions on your paper. Note there are two questions so there will be two predictions). (4 pts)

## Equipment:

(2) potato cubes | (2) small beakers | (1) balance | |

tape, marker & ruler | fresh water | table salt | graduated cylinder |

## Procedure:

- Make 25 ml of a 3% salt water solution. Show your calculations for the amount of NaCl needed. (2 pts)
**Carefully**cut two potato cubes. Each cube should be about 3cm³ .**Gently**flip the cubes around on a paper towel to remove**excess**surface moisture.- Mass the potato cubes. Each cube will likely be different.
- Place a potato cube in each of the beakers.
- Nearly fill the first beaker with fresh water. Label the beaker.
- Nearly fill the second beaker with 3% salt solution. Label the beaker.
- Set aside the beakers as directed by your instructor.
- The next day,
**gently**flip the cubes around on a paper towel to remove**excess**surface moisture and mass the potato cubes.

## Data Section:

- Record the before and after mass of each cube. (4 pts)
- Record your calculations for the percentage change for each mass. (4 pts) Use this formula:
[(after mass - before mass) / before mass]* 100

- Use graph paper to graph the solution concentration (x-axis) vs. percentage potato cube mass change. (4 pts)

## Analysis:

Answer these analysis questions in complete sentences.

- For each solution did the potato cube mass increase, decrease or stay the same? (2 pts)
- Why would the potato cube change mass? (2 pts)
- Make a before sketch of a typical plant cell and two after sketches: one for the fresh water cube and one for the salt water cube. (6 pts)
- Describe the two solutions in terms of being hypotonic, hypertonic and isotonic solutions. (2 pts)
- Looking at your graph, estimate what salt concentration would be an isotonic solution for the potato cube? Explain your reasoning. Hint: what would a 0% mass change mean? (4 pts)