Purpose: To see the effects of tonicity’s on potato cells. Background: Osmosis is the diffusion of water across a differentially permeable membrane due to concentration differences. Tonicity is the concentration of solutes. The potato cell has 3% of dissolved materials. Hypertonic is when the solution has more dissolved materials outside the cell than inside. The cell will lose water this way and shrink. The potatoes in the 5% salt solution will shrink. Hypotonic is when there is less solute dissolved materials inside the cell. The cell will gain water and get bigger.
The potatoes in 1% salt solution will get bigger. Isotonic is when the solution has equal amounts of solute inside and outside the cell. These are all different types of concentrations of solutions. The cell will not be affected at all. The potatoes in the 3% salt solution will have no change. If a cell is put into a hypertonic solution, the water will move out of the cell to balance the concentration difference. If a cell is put into a hypotonic solution, the water will move into the cell. If the cell is put into an isotonic solution, there will be no net movement.
Hypothesis: The potatoes placed in the 5% salt solution will shrink (hypertonic), the potatoes in the 3% salt solution will have no change (isotonic) and the potatoes in the 1% salt solution will get bigger (hypotonic). Materials: – 2 small white potatoes – 4 150 ml styrofoam cups -balance -30 ml distilled water -30 ml each of a 5%, 3% and 1% salt solutions -Single-edge razor blade -Toothpicks -masking tape Procedure: 1. Make sure goggles are on. 2. Take two small white potatoes and use a single-edged razor to cut them into eight 1. cm cube pieces. 3. Label the first cup 5% salt solution and add 30ml of the 5% salt solution. 4. Label the second cup 3% salt solution and add 30ml of the 3% salt solution. 5. Label the third cup 1% salt solution and add 30ml of the 1% salt solution 6. Label the last cup 0% salt solution and add 30ml of distilled water. 7. Take eight tooth picks and eight small pieces of masking tape to label the potato pieces. Label one toothpick with the number 1 and a second toothpick with the number 2. Each cup will have 2 potatoes representing each trial. 8.
Measure the mass (g) of each potato piece and record them in a data table. 9. Take 1 toothpick with tape and stick one toothpick per potato. 10. Place in each cup 2 labeled potatoes and leave them over night. 11. Take the potatoes out and measure their mass with the tooth picks out. 12. Record data 13. Calculate the percent change by using the following formula: Amount of increase or decrease x 100 = % change Mass before 14. Compare data with the before and after mass Data: Trial 1Trial 2 Mass Before (g)Mass After (g)Mass Before (g)Mass After (g) 0% 1% 3% 5%