1) Using the cork borer take six samples of potato from the same potato. Then using the scalpel cut the pieces of potato so they are twenty millimetres long. Remember to weigh the potato with the blotting paper pieces and record their weight in a table.
2) Take eight test tubes and place them in a rack, then add the different standard solution and distilled water, the distilled should be more than the standard solution.
3) Place the potato pieces in the test tubes; make sure they are covered with solution. Leave them there for ten minutes.
4) Take the potato pieces out carefully and blot it using blotting paper, measure their length and weight with blotting paper, record this in your table and repeat twice more
Diagram:
Key Factor:
The key factor in my experiment is the concentration of the sugar solution ranging from 1ml to 4ml I also used distilled water. I think that this is a suitable range of concentrations. The factors that I will control are the points in my fair test
Fair test:
To make this experiment a fair test I will use the same…
· Length potatoes- so that there is the same length of potato for osmosis to take place in.
· Room temperature- so that this doesn’t affect the rate of reaction.
· Size cork borer- so that the size of the potato doesn’t vary.
· Amount of sugar water- so that the potato pieces have no more or less sugar solution to absorb.
· Amount of time potatoes are left in sugar solution. - so that I can record accurate results.
Safety:
Safety is an important aspect in every experiment, even if the experiment seems to be very harmless. This is why I’ll be taking this into consideration. I will be using a very sharp knife, which could injure someone if not handled properly. I will also be very careful that the solutions don’t get into our bodies internally, because we are not fully aware of the damage it could do to us. I will also wear my lab coats so that I won’t split sucrose solution of cloths.
Obtaining Evidence:
Analysing and Considering Evidence:
The graph gives the line of best fit for the percentage change in mass of the parsnips over the course of the ten minutes experiment. The graph is a correlation goes through the origin, because the line is straight, it means that the percentage gain and loss in mass and concentration are not directly proportional. However, there is a pattern on my graph, and this is, as the concentration of the solution increases, the percentage change in mass decreases. The graph shows that the percentages gain and loss in inversely proportional to the concentration. From the line of best fit that has been added in, it can be seen that all of my points were very close to creating a perfectly smooth curve. This shows that my results are fairly reliable. My graph fits in with my prediction of the experiment graph.
Evaluating:
The experiment was very successful in my opinion. I obtained a large quantity of very accurate results from which I was able to create informative graph. I think I took easily enough results for the amount of concentrations that I was using, and the time that I used for the experiment to last was enough to allow sufficient osmosis to happen and possibly find out the saturation point of the parsnips. The range of the concentrations was adequate but I would possibly create more concentrations if I repeated the experiment so that I would have more varied results i.e. 0.10g, 0.15g, 0.20g and so on. This way would have allowed me to me to also find out the isotonic point far more accurately as the one that I estimated is very approximate.
The cutting of the parsnip was the most difficult part of the experiment as although I was recording my results by mass, it could well have affected the surface area and so the overall rate of osmosis. If I were to repeat the experiment I would have possibly found a machine to cut the parsnip, as it would ensure that all the parsnips would be the same weight and dimension. As well as the parsnip I could have used a burette. This would ensure that I have an accurate amount of fluid in each.
Reference:
www.studentcentral.co.uk/coursework/essays
