Osmosis in potato and apple

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Investigating The Effect Of Osmosis On Two Different Plant Tissues

The aim of the investigation is to find out the effect water potential has on osmosis in two different plant tissue; apple and potato.

To help me on this investigation I decided to conduct a preliminary experiment. This allowed me to have an overall impression of the experiment, and I could spot any weaknesses in my experiment which I can modify to ensure that the real experiment has no flaws, so that the result obtained are accurate and reliable.

The preliminary experiment involved cutting five ‘chips’ of each tissue sample, to equal size, and placing each into different concentrations of salt solutions. After an hour, the samples were taken out of the solution and measured. The results and graph are in appendix 1.

Possible variables

There are a number of factors I shall be keeping the same:

  1. Temperature: the temperature must be kept constant throughout the experiment as it may affect the results, and the movement of water molecules.

  1. Volume of salt solution: the volume must be kept the same; in this experiment, each ‘chip’ will be immersed in 40ml of salt solution.

  1. Initial volume of plant tissue ‘chips’: this will be kept the same using a core borer.

  1. Initial length of plant tissue ‘chips’: this will be cut to 50mm

  1. Initial mass of ‘chips’: this is difficult to control, however each ‘chip’ will be the same mass and to 2 decimal place.

  1. Plant tissue type: all the samples will come from the same type (and age) of potato/apple to ensure that the investigation is kept fair and accurate.

  1. Time in solution: all the ‘chips’ will be kept in the solutions for the same period of time. The timing will be staggered, each chip will be placed in the solution two minutes after the previous so each have been in the solution for an equal period of time, and measured.

The factor that will be changed during the experiment is the concentration of salt solution.

Measurements

The measurements I will be taking during this experiment are mentioned above; the volume of salt solution, volume, length & mass of ‘chips’ and the time in solution. Also the concentration of the salt solution is measured when making the dilutions.

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In my preliminary experiment, I used 4 concentrations of solution; 0.00M, 0.25M, 0.50M 1M. This would not give me a reliable and precise conclusion therefore I will use a more varied range of concentrations.

Serial dilutions were made, the table below shows how the dilutions were made:

In my preliminary work, I used a measuring cylinder (accuracy of +/- 0.1ml) to measure the solution for the serial dilution. It is more accurate to use a pipette (accuracy of +/- 0.05ml), so I will use a pipette to enhance the reliability of the results.

The mass of the ...

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Here's what a star student thought of this essay

This piece is written coherently and uses technical terms throughout. One query is that the first person is used throughout: a more sophisticated piece would be able to write fluently without saying "I decided to". Tables were used well to support the investigation, and diagrams aided in explaining osmosis. This was a very well thought out piece of work, so it was a shame not to see any post-experiment analysis!

This essay is able to pick out the variables which could affect the investigation, posing a solution to keep them controlled. It is made clear that the controlled variable is the concentration of salt solution. Terms regarding precision and reliability are used well, but validity is not mentioned. Validity could've been mentioned if the essay had analysed the results, comparing the outcomes with their hypotheses. The scientific terms when describing osmosis are strong, including water potential and partially permeable membrane.

This piece of coursework lays out the experiment incredibly well, including a preliminary experiment and a hypothesis, but it was a shame not to see any analysis of the final results. Without an inclusion of the results, a graph and some relevant analysis, this essay doesn't directly answer the question. If this was available, this piece would be a very strong example of an investigation.