Introduction:
All cells have membranes that are selectively permeable. In other words, they allow certain things in and certain substances are not allowed to enter the interior of the cell. The process by which water crosses membranes from regions of high water concentration to regions of low water concentration is called osmosis. Osmosis is the process whereby water moves across a cell membrane by diffusion. Diffusion takes place when the molecules of a substance tend to move from areas of higher concentration to areas of lower concentration. Involved in this process are hypotonic, hypertonic, and isotonic solutions. In this experiment, we learned about osmosis and diffusion through potato cores in different concentration of sucrose, (distilled water, 0.2, 0.4, 0.6, 0.8, and 1.0).
Topic:
How does Osmosis affect the weights of potato slices in different concentrations?
Hypothesis:
In solutions of higher concentrations, the potato cores will lose weight. Additionally, potato cores will increase in weight when placed in a solution of lower concentration.
Variables:
• Independent Variable - sugar concentrations
• Dependent Variable - post-experiment potato core weights
• Controlled Variables - amount of water, size of potato cores, weight of potato cores in the beginning.
Procedures:
Fill 6 plastic cups with different sugar concentrations – each with a different food coloring mixed in – but only fill them enough to cover the slices, not all the way to the top of the cup. Obtain potatoes and punch out equal-sized slices using the cork borer; they all must be the same size and have equal amounts of or no potato skins. Divide the 21 cores into 7 groups and weigh them separately. Using the balance, weigh each group of potato cores and record the data - the data should reflect the type of solution in the cup and the mass of the 3 potato slices that will be placed in the cup. Place the potato core sets in their appropriate cup at about the same time and set a timer for approximately 20 minutes, noting any observations (color change, floating/sinking, etc). When time is up, remove the slices from the cups and blot them dry to remove any excess water weight. Record the potato groups' final mass and then wash and dry the equipment and work area. Begin calculations for each set of potato slices, using the using the formula (final mass‐ initial mass)/initial mass x 100 to calculate the percent change in mass. Make sure to keep track of the positive and negative changes as they occur, then graph results and determine the solution concentrations.
• Initial Potato Masses:
Yellow = 7.03g
Clear/Distilled Water = 5.55g
Blue = 7.24g
Green = 6.98g
Orange = 7.31g
Red = 7.11g
Purple = 7.48g
