October 12th 2012
Purpose: The purpose of this lab is to investigate the effects of osmosis on a potato cell as it is immersed for a period of time in solutions of different water concentrations.
If the potato is immersed into the distilled water, then it will be the heaviest out of the three. This is because water is at the lower is moving toward the area of higher concentration, which in this case is the potato. This solution is a hypotonic solution which is exactly opposite as a hypertonic because the outside of the cell has a higher concentration of water than the inside, and so the water on the outside goes inside the cell. As the water moves inside of the potato, it will cause the potato to gain weight and become heavier.
If the potato is immersed into the saline solution, then it will stay the same. The concentrations of the two are the same, so the water will not have to move anywhere to become equal. That is because, this solution is an isotonic solution meaning that its solutes are in equilibrium, or are solutes that have the same concentration. This causes a concentration to diffuse across the potato cell membranes in both directions. The saline solution is at the same concentration as the potatoes so the water would not have to move to become equal.
If the potato is immersed into the saturated solution, then it will become the lightest out of the three. This is because the solution contains a lot of salt. The salt does not dissolve because of the large amount already in the water, it to be saturated. During the process of osmosis, the water leaves the cells of the potato to the solution outside. This is happening because the water on the outside of the potato is at a higher concentration than the water inside of the potato. This causes weight the potato to lose weight and become lighter. This solution is a hypertonic solution, meaning the solute concentrations are different inside and outside the potato cell so the outside has higher solute concentration than the inside of the cell. The solutes with higher concentration of water always like to go to solutes with lower concentrations of water.
Osmosis is the movement of water across a semi-permeable from an area containing a low concentration of solute to an area containing a high concentration of solute. As the salt solution becomes more concentrated the potatoes will loses weight, less water would move into the potato by osmosis but in this solution. The potato in the distilled water will be the heaviest because the water is at a higher concentration, so it will move into the potato. The potato in the saline solution ill stay the same because the concentration of solutes is the same so water will not have to move anywhere to become equilibrium. The potato in the saturated solution will be the lightest because the water from the potato will travel to the solution to even out the concentrations because the water in the potato is at higher concentration. The potato in the saline solution will stay the same.
Independent Variable: 3 Different solutions of water (Distilled, Saline, Saturated) Dependent Variable: Mass of potatoes
Controlled Variable: Amount of solution, size of potato, time, and temperature of water
1. Three plastic cups
4. Measuring Scoop
5. Water (150 ml x3)
6. Graduated Cylinder
7. Nine uniform, cylindrical pieces of potato
8. Electronic Weigh scale
1. Fill one of the cups with saline solution.
2. Fill the other cups with saturated solution
3. Fill the third cup with distilled water
4. Cut the potatoes into cylindrical pieces
5. Separate 3 pieces of potatoes for each cup of solution 6. Blot out some of the water on the potatoes.
7. Weigh the potatoes and record masses.
8. Then place the 3 pieces into each of the cups of water....