Definition of osmosis:
Osmosis is the passage of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration.
Aim:
To see how concentration affects osmosis on a potato.
Prediction:
I predict that the higher the concentration of molar solution, the more the potato chip will weigh.
Plan:
A potato will be cut using a cork borer and knife to equal lengths; this will keep the surface area equal. Then the starting mass will be measured. To each test tube a cut piece of potato will be added and its mass labeled on paper. These will be left for 5 minutes. Then the potato pieces will be removed, dried by with a paper towel and weighed. The results will then be put into table form.
Prediction:
For this investigation I predict that the higher the solution, the potato will be higher in mass. I think this because osmosis is a type of diffusion, and the stronger the solution the more the potato chip will absorb. This is because the high water concentration will move across to the low water concentration.
Apparatus:
1 Molar sugar solution, distilled water, potato, cork borer, mass balance, boiling tubes, knife, measuring cylinder, stopwatch, paper towels.
Method:
- I will use one potato for my experiment.
- I will cut a cylinder chip using a borer.
- Using a ruler I will make sure the length of the chips were the same.
- I will weigh each of the chips to 2 DP.
- I will then measure the chips in cm.
- I will take 6 test tubes, for the chips.
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and filled each with 10cm3 of 1 molar sucrose
- I will then inserted the potato chip in the test tube,
- Then start the timer.
- After 5 minutes I will take them out and weigh the chips.
- To finish it off I will record my results in table and graph form.
Here is a table of my results.
Evaluation:
The accuracy of the investigation was very good, however, when the potato was dried to remove surface liquid it was not automatically done the same on each potato, a better way of drying the potatoes would have made the experiment even more accurate.
For a more accurate result, we could have increased the (M) by 0.1 instead of 0.2. Also, there could have been a variety of plant such as carrot etc.
Conclusion:
My conclusion is that the higher the solution, the lower the potato chip grew in mass. When there was 0.0 M of sugar solution, the mass of the potato grew a lot, but when a solution was added, the mass always decreased.
This is because of the diffusion which takes place in osmosis. If the solution outside the cell has a low concentration, the cells become affected because water is flowing into them, if the solution outside the cell is of high concentration the water flows out.
Overall I feel this experiment will help me in my exams because I now understand more about diffusion and osmosis, and what it takes for osmosis to occur.