Osmosis and Salt Concentration

9 September 2016

Which saltwater concentration will have the most damaging effects on potato cells? Introduction Osmosis is the diffusion of water across a selectively permeable membrane. Generally, water moves from a lower solute concentration into a higher solute concentration. This movement of water occurs due to the need for the concentrations in the cell and in the solution to be at equilibrium. A solution with a low solute concentration and a high water concentration is referred to as hypotonic.

A solution with a high solute concentration and a low water concentration is referred to as hypertonic. When two solutions are isotonic, there is no net flow of water because the solutions have equal concentrations. When a cell is put into a hypertonic solution, it will lose water and plasmolysis- shrinking of the cytoplasm- may occur in plant cells. Without this water there is little pressure inside the cells and the plant can no longer support itself against the pull of gravity. When a cell is put in a hypotonic solution, it will gain water and become turgid, or swollen.

Osmosis and Salt Concentration Essay Example

In plant cells, this is the state in which the concentrations are balanced due to the wall pushing back on the cell and the plant is strongest. When they are in a hypotonic solution, the cells become inflated with water and the plant stands upright and is able to overcome the pull of gravity. Aim The aim of this experiment is to find out which saltwater concentration is most hurtful to potato cells and use this model to see how saltwater affects plants in general. Hypothesis The highest salt concentration (15%) will have the most damaging effects on the potato cells.

Due to the solution’s high solute concentration and low water concentration, water will move into it and out of the cell, causing the cell to become plasmolyzed and weak. Control: the mass of each potato cylinder before it is put in any of the solutions. Independent variable: the solutions of varying salt concentrations. Dependent variable: the mass of each potato cylinder after it is put into the different solutions. Materials and Methods Materials for Saltwater Solutions 1. Table salt 2. Tap water 3. 4 Beakers 4. Pan 5. Wooden spoon 6. Teaspoon 7. Bunsen burner/ stove top . Graduated cylinder Procedure for Saltwater Solutions 1. Heat up 100 ml of tap water in a pan above room temperature, but do not boil.

After the water is heated up, turn off the fire and start adding salt with a teaspoon. Stir the water with a wooden spoon as you sprinkle in the salt. Keep observing the water as it is being stirred. 3. When the water approaches 100% concentration, the salt crystals will no longer dissolve and they will remain whirling around in the water. Let it sit for a few seconds and then check to see if the crystals can still be seen. . If they have dissolved, then add more salt until they remain sitting at the bottom of the pan, at which point the solution is 100% saturated and can’t dissolve any more salt crystals. 5. Let the water cool to room temperature. 6. After it reaches room temperature, carefully pour the liquid into a beaker labeled “100% salt concentration”. Do not allow the remaining salt crystals to go into the beaker. 7. Label another beaker “10 % salt concentration. ” 8. To make the 10% salt concentration, pour 100 ml of tap water into the beaker.

Then pour 10 ml of the 100% salt concentration into the same beaker. 9. Label another beaker “13 % salt concentration. ” 10. To make the 13% salt concentration, pour 100 ml of tap water into the beaker. Then pour 13 ml of the 100% salt concentration into the same beaker. 11. Label another beaker “15 % salt concentration. ” 12. To make the 15% salt concentration, pour 100 ml of tap water into the beaker. Then pour 15 ml of the 100% salt concentration into the same beaker. Materials for Osmosis Experiment 1. Potatoes 2. Electronic balance 3. 20 Plastic cups 4. Cork borer 5.

Knife/ razor blade 6. Ruler 7. Distilled water 8. Salt concentrations (10%, 13%, 15%) Procedure for Osmosis Experiment 1. Separate the 20 cups into four groups of five. 2. Label one group “distilled water” trails 1-5. 3. Label other group “10% salt concentration” trials 1-5. 4. Label other group “13% salt concentration” trials 1-5. 5. Label other group “15% salt concentration” trials 1-5. 6. Use the cork borer to make 20 potato cylinders. They should all be 3 cm long. 7. Use a knife or razor blade to trim the cylinders so that they are all the same size and use a ruler to measure them. 8.

Use an electronic balance to measure the mass of all the cylinders and record this information. This should be the same for all 20 cylinders. 9. Take five potato cylinders and put one in each of the five cups for trials 1-5 labeled “distilled water. ” 10. Repeat step 9 for the other three groups of salt concentrations. 11. Let the potato cylinders incubate for 40 minutes. 12. After 40 minutes, take the potato cylinders out of their concentrations and use a paper towel to blot off the excess solution. Use the electronic balance to measure their new masses and record this information.

The graph above shows the total change in mass of the potato cylinders before being soaked in salt solutions compared to after being soaked in salt solutions. The change in mass was averaged from five trials from each salt concentration. Analysis The data results show that the masses of the potato cylinders decreased when they were soaked in all the salt solutions, or the hypertonic solutions (the 15% salt concentration solution showed the most loss in mass). This means that water was moving out of the potato cells and into the salt solutions, which suggests that potato cells have a salt concentration of less than 10%.

The masses of the potato cylinders increased, however, when they were soaked in distilled water, or the hypotonic solution. This means water moved into the potato cells, which demonstrates that potato cells have a salt concentration of more than 0. In the first graph, we can see the beginning mass compared to the ending masses. The beginning mass is an average of 0. 82 grams and has a standard deviation of 0 because all of the masses were the same. This suggests that any value outside of 0. 82 shows a significant effect on the potatoes. Conclusion and Evaluation

The hypothesis was correct. The highest solute concentration (15%) has the most damaging effect on the potato cells. The water moved out of the cell when placed in the hypertonic solution and it caused the cell to become plasmolyzed. Using potato cells as the model, we can generalize that all plant cells will plasmolyze and the plants will wither and die when placed in a solution of higher solute concentration than the plant cells. This is the reason plants have to be watered constantly with water that has a lower solute concentration than the plant cells.

They must remain in a turgid state in order to thrive, and this only occurs when the cells are placed in a hypotonic environment so the water can move out of the solution and into the plant cells. For this same reason, vegetables are sprayed with water at grocery stores. The plants are no longer attached to a source of nutrients where they can get water, so they are sprayed with water to keep them healthy and prevent them from withering and dying. Although this investigation is reliable, there are some errors that contribute to its decrease in validity.

The number of trials performed is a drawback. There were only five trials performed per sample which is not enough to make a large scale rule for the results of the investigation. Also, any outliers in this small set of data would alter the results completely and make them inaccurate. A larger experiment, perhaps with 500 trials per sample rather than five, would offer more accurate results. However, in the interest of time and with regard to financial constraints, the resources are not available to repeat the investigation multiple times.

There is also some human error involved that may contribute to somewhat inaccurate results. When measuring the water and the salt solutions using a graduated cylinder, there may be instances when not all the water is transferred from one place to another. This may cause slightly inaccurate measurements of water and salt concentrations, which leads to slightly inaccurate results. There is no solution for human error because it will always be a part of any investigation, however, it is possible to be more careful when measuring and transferring solutions.

Another contributing error is the precision of the materials used, such as the ruler, the graduated cylinder and the electronic balance. The ruler used to measure the potato cylinders measures only to the nearest millimeter and thus has a margin of error of ±0. 1 mm. The graduated cylinder has a margin of error of ±0. 01 ml because it measures to the nearest tenth of a milliliter. The electronic balance, which is probably the most important measurement tool in this investigation, only measures to the nearest hundredth of a gram.

This makes it difficult to show an accurate difference between masses because they can sometimes be very close. A solution to this problem would be to use more accurate equipment. However, financial constraints must once again be considered. The more precise the tools are, the more expensive they are, and in a low budget investigation more precise equipment is not a realistic option.

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