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Potato cylinders

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Introduction

Potato cylinders VARIABLE NON- VARIABLE Solution concentration Surface area Solution volume Duration of experiment Temperature Solution Conditions The variable I am going to change is the sugar concentration. Prediction I think that the potato cylinder will get shorter if the sugar concentration is increased. This will happen because of osmosis, osmosis is the movement of a liquid through a cell membrane from a lower to a higher concentration. The water in the potato is a lower density than the sugar solution, therefore when the water exits the potato through the membranes the potato will gradually shrink. A diagram to show osmosis Water = Sugar = The water molecules can pass through the gaps but the sugar particles cannot fit through. The water molecules are passing through to the left-hand side to balance the quantities. Further information on potato plant cells: Plant cells always have a strong cell wall surrounding them. When they take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in dilute solutions. ...read more.

Middle

Sections of potato will be cut using a scalpel and will be measured using a ruler. This part of the preparation must be done very accurately as a change in the surface area may allow more or less osmosis to occur. I will be placing one potato cylinder in each test tube I am also working with two other people so I can take an average for each tube. I will use 10 ml of each concentration of sugar solution and once in the test tubes they each will be labelled. The potato pieces will then be placed in the different test tubes and then left for 24 hours. Then the potato cylinders will be removed, the surface solution removed using paper towels and then they will be re-measured. This will hopefully produce more accurate results from which I will be able to draw a more accurate conclusion. Method 1. I took two average sized ground potatoes and checked that they were both healthy and hard. 2. Using a potato core of about 0.5cm in diameter I cut 5 little sections of potato. ...read more.

Conclusion

The graph is a curve that slopes downwards and does not go through the origin. Because the line is not straight and does not pass through the origin, it means that the percentage gain and loss in length 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 length decreases. The graph shows that the percentage 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. It shows that the potato cells increase in mass in solutions with a high water concentration and decrease in mass in solutions with a low water concentration. Carrying the experiments a few more times to make sure the results were more accurate could have extended the investigation. We could have also tried a few more concentrated solutions to see if the rate of osmosis increased. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

***This is a nicely presented piece of work but it needed to be organized more carefully to enable the reader to follow the experimental plan. The recording of results was confused and the data analysis was weak. There was no evaluation or background research to help inform the plan.
To improve:
Planning:
The candidate decided for themselves factors such as the range, interval and number of repeat readings that they should take, and the variables that needed to be controlled, but key statements such as the name of the sugar to be used were omitted in some sections. The candidate should ensure that all details are recorded so that someone else could carry out their plan without asking for further information.
The candidate should independently research their experiment and include background references to help inform the plan and carry out a more thorough risk assessment.
Carrying out:
The student appears to have collected some sensible data but needs to ensure that all data in tables has the correct heading and units. There were several other data tables included with no indication as to what they refer to.
Analysis and Evaluation:
The candidate did link their results to the prediction but did not explain them fully using relevant background theory. The analysis was confused by references to other results of unknown source.
The candidate referred to using percentage change in length to analyse the data which is a good idea but these calculations or graphs using these figures were not in evidence.
They need to evaluate the method of collection and the quality of the resulting data and analyse further secondary data drawn from the same topic area as their investigation.

Marked by teacher Stevie Fleming 29/05/2013

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