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Investigation to find the isotonic point of potato cells

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Investigation to find the isotonic point of potato cells Apparatus In this experiment I used: Test tubes, potato borer, potatoes, water, test tube rack, a mass balance, different concentrations of salt, beakers, a 10ml syringe and a 1ml syringe. Diagram Method * We set up the apparatus, as above. * We made up the different salt concentrations.(As shown overleaf) * The potato borings were cut to a size of 10cm and then weighed on the mass balance, and their length was checked. * They were then added to the test tubes and then left for 2 hours. Variables In this experiment there are quite a few variables, they are: * The salt concentration. * Temperature - This affects the energy the particles have. On the first day of the experiments, the temperature was 22oc, and on the second day the temperature was 21oc. * Potato mass at the start of the experiment. * Type of potato - We used a different type of potato during the trial experiment and the actual experiment. * Presence of peel - Some peel might have been left on the potato boring which would affect its surface area. ...read more.


the temperature will not change that much, and will not affect the outcome to much, as it was all the results were taken in the same morning. * All of the above variables must stay the same except the concentration, and there should be no peel left on the potato chip, for the above reason. * There should also be the same volume of salt solution each time. Prediction In this experiment I predict that as you increase the salt concentration, the mass of the potato will decrease through osmosis, as water particles will leave the cells, due to a lower water concentration outside the potato. We will know when the isotonic point is reached when the potato no longer changes in mass. (For an explanation of osmosis see below) Background knowledge Osmosis - This is the diffusion of water particles down a concentration gradient, through a selectively permeable membrane. Selectively permeable membrane - This is a membrane that only lets some particles pass through, and not others. Flaccid - A flaccid cell is one that contains little water. ...read more.


This happened because the concentration of water concentration out side the chip was less than the concentration of water particles inside the chip. Evaluation I think that our results are accurate, even though some of points are off the trend line. There are a few problems with our results. I think that there are a few improvements that we could of made to the experiment, to make it more accuratly. We could of have used a burette, to make the solution more accurate. We measured all of our measurements to 2 decimal places. I think that our results would be very reliable as nothing went wrong during the experiment. The only factor that could have changed the out come of the results was the temperature change over the two days that the experiment was carried out. The temperature difference was only 1oc and so it wouldn't have made too much difference to the results. Extension To check to see if this is the same for all types of potatoes, and all different ages of potato, I would use a small range of concentrations, and use different types of potato. I would use old, new, and different types of potatoes, to see if the isotonic point changes with these factors. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a good attempt at a report, although it is very brief.
1. The background knowledge section should be at the start and needs to contain relevant information on this project.
2. The method is good but incomplete.
3. The information on variables needs to be brought together under one subheading.
4. The data collected has a good range and number of repeats.
5. The analysis and evaluation both lack detail.
*** (3 stars)

Marked by teacher Luke Smithen 08/05/2013

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