Osmosis Lab

Problem: To what extent does the concentration of a sugar solution affect the mass of potato cubes / cells?


Define the following solution types:




Hypothesis: (predict what % water potato cells have inside them):

Experiment: 1) Label 5 plastic cups 100% water, 95% water 5% sugar, 90% water 10% sugar, 85% water 15% sugar, & 80% water 20% sugar.

2) Pour the same amount of the appropriate concentration of sugar water into each. There needs to be enough to cover the potato pieces.

3) Cut 15 potato cubes approximately 1cm by 1cm by 1cm using a scalpel.

4) Place 3 potato cubes into each cup after taking the mass of the potato cubes using the triple beam balance to the nearest 1/100g (2 decimal places).

5) Allow the solutions and potatoes to sit until the end of the period.

6) Remove the water from the potato cubes. Use a paper towel to lightly pat them dry. Take their mass.

7) Calculate the mass difference and the percent change.

8) Graph the percent change using a line graph.

9) Find the percentage water in potato cells by seeing what percentage is on the X-axis where the graphed line crosses it.

10) Find the correlation coefficient for the MOLAR CONCENTRATION and % CHANGE.

Data Table & Graph:

% Concentration
A) Initial Mass (g)
B) Final Mass (g)
C) Mass Difference (g) (B-A)
% Change (C/Ax100)
80% water
85% water
90% water
95% water
100% water

Paragraph A of "Discussion" (please use this as a guide for your 1st paragraph in your lab writeup)

1) What did you predict in your hypothesis? According to YOUR data, what is the water content of potato cells?

2) Which solutions were hypertonic? How do you know?

3) Which solutions were hypotonic? How do you know?

4) Which solutions were isotonic? How do you know?

5) What was the relationship (correlation) between PERCENTAGE WATER and MASS INCREASE in potato cells?