I predict that the stronger the molarity of the salt-solution the shorter the length of the potato and the less the potato will weigh. And the weaker the molarity, the longer the length of the potato and the more the potato will weigh in comparison to the potato in the higher molarity solution.
Apparatus
- 2M NaCL solution
- Boiling tubes
- Measuring cylinders
- Distilled water
- Large beakers
- Potatoes
- Cork borer
- Thermometer
Method
There are a number of controlled variables that change the rate of osmosis. They include concentration, heat, pressure and surface area. These variables have been controlled in their own individual ways. The concentration is changed when water is added to it. The heat is kept constant as the beaker in which the test tubes are in is kept in a water heater, which keeps the water at a specified temperature. The pressure and the surface are kept constant, because each potato is the same size and width.
Here is the step-by-step guide to what was involved in my experiment:
- Set up the apparatus and prepare to get potato samples.
- Using the cork borer, make as many samples of potato that you want.
- Make the solutions and prepare to add the potato samples to it.
- Each solution is made up differently to test the potatoes to various molarities:
- 20cm³ salt (NaCL) solution and 0cm³ water
- 15cm³ salt (NaCL) solution and 5cm³ water
- 10cm³ salt (NaCL) solution and 10cm³ water
- 5cm³ salt (NaCL) solution and 15cm³ water
- 0cm³ salt (NaCL) solution and 20cm³ water
- Add the potatoes to the different solutions and put them in a beaker.
- Label the test tubes and beaker.
- Place the beaker in the water heater, which will keep the temperature constant.
- After a certain amount of time, re-weigh and re-calculate the length of the potato and state the difference.
- Record the results.
Diagrams
Key
I started my experiment and recorded the times from when the reaction started. I added the potato to the solution at 12.41pm and took them out at 2.46pm. This means that the solution had 2 hours and 5 minutes to react. During this amount of time there has been a visible difference.
Conclusion
As I predicted at the beginning of the experiment, I said that ‘the stronger the molarity of the salt-solution the shorter the length of the potato and the less the potato will weigh’ and ‘the weaker the molarity, the longer the length of the potato and the more the potato will weigh in comparison to the potato in the higher molarity solution’. This prediction came true. The test tubes with the greater molarity and greater concentration of the NaCL solution, shrunk the potatoes that were in them, and the potatoes in the salt solution with a lower concentration did not shrink as much.
When the potato sample was added to the 0.0M solution, the weight of the potato increased. This is because the concentration is higher in the potato than in the distilled water, so by osmosis, the water molecules went from a higher concentration to a lower concentration. This occurred to balance out the concentration.
Evaluation
In this experiment, there were various different things that I could have done to change and improve the outcome of the results.
The accuracy and how detailed and accurate the results are, are a major part of the experiment that can change the results.
Not all of my results may be reliable. If I had made a slight mistake, it would have changes all of my results.
And if I had more time to do the experiment, I could have got more results. This variety in results would have made my conclusion more precise.
If I had left the potatoes in the salt solution for longer, then there would have been a large change. As I had only left the potatoes in the solution for about 2 hours, the reaction that took place would not have been as large, compared to if the potatoes were reacting for a longer period of time.
