Potato in Solutions Activity (mass)
- What is the mass change of a potato cube in fresh water?
- What is the mass change of a potato cube in salt water?
(Record your predictions on your paper. Note there are two questions so there will be two predictions). (4 pts)
|(2) potato cubes||(2) small beakers||(1) balance|
|tape, marker & ruler||fresh water||table salt||graduated cylinder|
- 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.
- 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)
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)