• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16

Osmosis Investigation

Extracts from this document...

Introduction

Skill Area P: Planning and Experimental Procedures Aim The aim of this experiment is to demonstrate the process of osmosis in potato tissue. To do this I will cut strips of potato, immerse them in various concentrations of sucrose solution and examine the change in length of the strips, if any. Preliminary Study To set up a range and interval for my experiment I carried out some preliminary work to give me an indication of what the change in length would be like. I used three concentrations, 0, 0.5 and 1.0 molar (1M) and immersed three 50mm strips in each solution for 15 minutes. The results are shown in the following table: - Molarity Length after immersion Average length after immersion Change in length Percentage change 1st strip 2nd strip 3rd strip 0 53mm 50mm 47mm 52mm 2mm 4% 0.5 51mm 49mm 49mm 50mm 0mm 0% 1.0 52mm 51mm 48mm 48mm -2mm -4% In this preliminary study, the equilibrium concentration, that is where there is no change in length, is approximately 0.5M. A range of concentrations either side of this value should therefore give me a satisfactory set of results. Apparatus/Materials 6 test tubes Test tube rack Scalpel Cutting board Vernier 20cm3 Graduated pipette Stopwatch Various sucrose solutions Potato Distilled water Planned method I will first obtain 5 sucrose solutions - 0M, 0.2M, 0.4M, 0.6M, 0.8M and 1.0M. (These are all available from stock and made up by science technicians). ...read more.

Middle

As the difference between the water potential is less however, I think less water will be taken in than in the 0M solution and the increase in length will be smaller. In solutions stronger than 0.4M, I predict the potato strips will decrease in length. This is because above 0.4M the external solution will be of a higher concentration than the cell sap. The sucrose solution will have a more negative water potential than the cell. This means that water will leave the cell by ex-osmosis and give a plasmolysed state to the cell. A plasmolysed cell is one where the protoplast is completely pulled away from the cell wall (see diagram below). As the concentrations increase, the difference between the two water potentials of the cell and the solution will increase so I predict more water will leave the cell. Skill Area O: Obtaining Evidence I followed my original plan and did not make any changes to the proposed method. I used all the apparatus listed in the planning section. All safety procedures were carried out and no-one was injured during the experiment. All results obtained are shown in the table below. Results Molarity Length at end of experiment (mm) Average length after immersion (mm) Trial 1 Trial 2 Trial 3 0 53.46 53.24 52.40 53.03 0.2 51.52 52.63 52.24 52.13 0.4 49.96 50.71 49.68 50.12 0.6 48.64 48.13 48.84 48.54 0.8 48.45 48.39 48.15 48.33 1.0 47.80 48.09 48.23 48.04 Skill Area A: Analysing Evidence and Drawing Conclusions In the table below, ...read more.

Conclusion

If I were to redo this investigation I would suggest the following changes: * I would make sure a number of people were placing the strips in the solutions reducing the risk of one set of strips having more time for osmosis to occur. * I would use a cork borer as this would give me a uniform shape and keep the surface area constant. * To improve the reliability of my results, I could increase the number of concentrations by going up in intervals 0.1M not 0.2M (i.e. 0M, 0.1M, 0.2M, 0.3M...). This would give me more points to plot to improve my line of best fit. * If I didn't have time restrictions, I would leave the potato strips in the solutions for 24 hours, as this would give more time for osmosis to occur and stabilise. * Finally I would put strips in separate test tubes, as this would prevent the risk of strips touching and reducing the surface area for osmosis. To provide additional evidence for conclusions, I could repeat this investigation measuring the mass of the potato strips because this would mean that all over change was taken into account (change in all 3 dimensions). I could also investigate the effect of various concentrations of sucrose solution on different types of potatoes (e.g. sweet potato, new potato). Also I could compare the effect of various concentrations of sucrose solution on different types of vegetables (e.g. swede, parsnip, and carrot) and also see if the dynamic equilibrium varies with different tissues. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Life Processes & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Life Processes & Cells essays

  1. Marked by a teacher

    Find the rate of osmosis in different vegetables (Carrot, Potato, Swede, Parsnip and Sweet ...

    3 star(s)

    natural sugar in it, hence more osmosis will occur, and the vegetable will have a larger size gain, of water. Due to the vegetables being in 0.2M sucrose solution I predict they will all gain mass, but varying concentrations of sugar will alter the results.

  2. Osmosis Coursework. Investigation Of The Effect of Different Concentrations of Sucrose Solution on Potato ...

    In this case the cell will stay its original shape and there will be no change in mass or size. This is called an isotonic solution. This is when the solution inside the plant cell is of equal osmotic potential to the solution surrounding the cell.

  1. Osmosis investigation

    blot both sides of my potato chip as this careless mistake has made deemed my results unreliable. Another reason for anomalies may be that in every boiling tube there were 3 potato chips. This could have affected the rate of osmosis because all the potatoes were touching, leaving some surface area covered and therefore unable for osmosis to take place.

  2. The endeavour of this investigation is to ascertain if there is any effect of ...

    The experiment also showed that the equilibrium point was changing between each trial so therefore they should have used an average of the three trials and used this as the final set of results to actually be able to find or conclude any findings Advantages Good assortment of sucrose concentration

  1. Osmosis is defined as 'the movement of water molecules from an area of high ...

    2g salt lost around the same mass, whereas with the chips in 3g salt G and F lost more mass than E. The second graph shows the change in mass of the chips. In theory this graph should be quite useful as I can guess the change in mass of the chip that has 5g salt in the water.

  2. Planning and Experimental Procedures.

    Fair Test: To create a fair test certain aspects of the experiment will have to remain constant whilst one key variable is changed. I have chosen to vary the concentration of the sugar solution to provide a varied set of results.

  1. Determination of molarity of cell sap in potato tubers.

    The solution on the left is more concentrated because the sugar molecules are now hydrated and so have stopped the water molecules from moving freely and thus there are less water molecules present in the solution. This is usually called water of crystallisation.

  2. An investigation to demonstrate the effect of different sucrose concentrations on potato tissues.

    After the 40 minutes had passed, I drained out the solutions in the sink 11. The potato chips were taken out of the test tubes and dried using a paper towel. 12. Each chip was then weighed using accurate electronic scales and the results were recorded.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work