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biology- osmosis investigation

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Introduction

Preliminary work Before I started my investigation I spent time deciding how I was going to find the results. I looked at various possibilities for variables and how I could keep these the same. I also did small separate experiments to make sure that the measurements that I had chosen were suitable in comparison to what was being tested. It is important to do preliminary work so that you have a clear method, and know what you are specifically what you are doing for each part of the experiment. This is to prevent too much variation between the results data due to different methods (even if only slightly) when carrying out the experiment. The preliminary work informs my plan of the method and also checks that the method is a reachable one that it can be carried out with my facilities. The preliminary work has showed me the measurement I need to use and the apparatus will need. Here are the questions that I asked myself when doing the preliminary work: * How to cut the chip? Out of a range of possible apparatus for cutting the potato I decided to use a cork borer. There was also a range of sizes that the cork borer came in I decided to use the size 6 version. ...read more.

Middle

I made the measurement this accurate by using a pipette to level the measurement so that I could add and take small amounts to make it to as close to 30cm3 as I could get. I then poured this into a test tube using a funnel to guide the liquid and prevent spillage. If there were any spillages I would re-measure and start that text tube again. I repeated this method for each concentration of sucrose. 3. The next step I took was to actually start the experiment, because I only have two hands and 6 chips needed to be placed into the solutions at the same time I had three people to help me. 3 people placed the potato chips into the test tubes and the other person started the stopwatch all at the same moment. 4. the next step was simply to wait for 24 hours so that we could then find the results 5. I repeated this experiment 3 times so that the results were more reliable. Diagram of Method Variables To keep our experiment fair we have to control all possible variables. We need to control them because if they change then we will not know if our results have been affected by these changes and the experiment will be too faulty to have any reliability. ...read more.

Conclusion

3. If the area surrounding the chip has a high concentration of sucrose therefore a dilute concentration of water, the cells will loose water by osmosis. Water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink this also causes the chip to become floppy. Evaluation I think that this experiment has been quite successful and has produced fairly reliable results but the procedure and any type of improvement still needs to be taken into consideration. * * On one of the graphs I have drawn error bars, these show me...........(size overlapping) * One of the main problems that I found when doing this experiment was that it was very difficult to get the time at an exact point, because I had to work around the school day and timetable. The only way this could have been overcome would maybe be to plan it so that it was when you didn't actually have school and could come into get the results exactly when it has been 24hours. The other way that it could have been done would be to leave the experiment for exactly a week. The problem though that then may be encountered would be that with a substance like potato it starts to rot. Also the liquid surrounding the potato might start to evaporate and * Improvements choice of equipment * Future work ...read more.

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Here's what a teacher thought of this essay

3 star(s)

***
An okay attempt at the investigation but it is still largely incomplete. The aim of the investigation was investigate the effect of osmosis on potato chips at varying concentrations, but there was no analysis of the results. The experiment seemed to have been completed accurately but the results were not recorded in an appropriate fashion to clearly show the reader how much length / mass had been gained or lost. The graphs reflected this, it was unclear what they were showing.
The analysis should have gone through the effect each concentration had on the potato chip and this should have been explained in an evaluation using the theory of osmosis. The theory that was included on osmosis was very good but it was not linked to the results; the control of the variables at the start of the report was also very good.

Marked by teacher Jon Borrell 08/01/2013

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