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

Investigate and find the water potential of baking potatoes and sweet potatoes in (N/mm2) using various strength solutions of sucrose (mol).

Extracts from this document...


16th March Biology Coursework Aim To investigate and find the water potential of baking potatoes and sweet potatoes in (N/mm2) using various strength solutions of sucrose (mol) Hypothesis I believe that the baking potatoes will have a less negative water potential. In the experiment they will not increase in mass at a lower of sucrose molarity than the sweet potatoes. Baking potatoes contain more water than sweet potatoes. This is clearly obvious, cut a baking potato into cubes and it releases a lot of water, more so than sweet potatoes. Water potential determines the rate of osmosis. Water movement form a high concentration to a low one is the means for testing the aim. Distilled water and other strength solutions will flow into the sweet potato more readily than into the baking potato. This is because baking potatoes have more water, and thus a less negative water potential. Sweet potatoes have less water content and will therefore have a more negative water potential. Both potatoes will have a lower water potential then the distilled water and other sugar solutions. As water diffuses into their cells they will increase in mass. The weight difference will be converted into a percentage so that the water potential can be determined. When plotted on a graph, percentage change of mass against solution molarity, the line of best fit will cross the x-axis. At this point the potatoes will not have increase in mass, their mechanical pressure will offset the solute potential. At this point there would be no diffusion gradient and osmosis would cease. The potatoes would have the same water potential as their surroundings. Using tables I can determine what the water potential is in kPa or N/mm2 by means of comparison using the graph obtained by this experiment. (See appendices i) Obviously the sweet potato and the baking potato would have different water potentials. Their lines of best fit would cross at different points. ...read more.


The thermometer must be out of sunlight because that could give a biased reading. Rinse out all components (not electronic like the stop clock or the thermometer) three times to remove impurities that could affect the accuracy of the solutions. Rinsing the equipment three times dilutes impurities by a greater factor than just doing it once. Using a borer cut out a whole cylinder of potato out of the baking potato. Using a white tile as a backboard, cut 108 slices of potato, taking more cylinders out of the potato then needed, of roughly the same width using a scalpel. Take care with the scalpel as it is much sharper than a normal knife. The white tile will protect the surface you are working on. The 108 slices will be sufficient for the entire experiment. 36 slices will be required for the different solutions, six to each test tube. The remainder will allow for two extra repeats. The potato slices must be the same width and diameter to have the approximately same surface area, this is a primary factor over differences in mass as they are generated into percentages later on. The surface area will affect how much water can enter the total volume of the potato slice. Label six test tubes with the values given below. Mix together the quantities of distilled water and 1.0 mol sucrose solution as directed below. Label Add Distilled Water Volume (ml) Add 1.0 Mol Sucrose Volume (ml) 0.0 10 0 0.2 8 2 0.4 6 4 0.6 4 6 0.8 2 8 1.0 0 10 You must cover then shake each test tube to mix up the sucrose and water, this will give an even water potential. The values of the mixtures give the molarity of the solution as said on the label. These molarities give a wide range of possible readings, sufficient enough to give a proper reading. ...read more.


This could also change the position of the line of best fit. Anomalous results could be caused by laziness or fatigue, or because the equipment was not washed well enough with distilled water before use. Also, if you do not keep wiping the scales and resetting it then the weights might be recorded wrongly. When making solutions it is important to check volumes in the pipette by looking at the level of the meniscus on a level plane and not at an angle, this could give differing volumes and inaccurate concentrations. The limitations of the experiment were that the slices were not kept for sufficiently long periods of time in their solutions, and this prevented the maximum effect of osmosis from being carried out and thus a more representative percentage mass change. In subsequent investigations, the time may be extended to seven and a half minutes to allow for extra diffusion of water. More accurate readings for mass change would give a more accurate value for osmotic potential. You could also find the optimum temperature to submerge the slices in, because the efficiency of the protein based water channels is dependent on their hydrogen bonds which are easily affected by temperature changes. A preliminary experiment could find this out by using a sucrose solution of 0.4 mol and trying different temperatures to see which one put on the most weight, which would therefore be the optimum temperature as the protein channels are working their best. Finding the best temperature would give more true values for mass change as the cells would be working at their best. This in turn would give a better osmotic potential value that was more accuracy. Appendices (i) Molarity (mol) Osmotic Potential (N/mm2) 0.05 -0.13 0.10 -0.26 0.15 -0.41 0.20 -0.54 0.25 -0.68 0.30 -0.86 0.35 -0.97 0.40 -1.12 0.45 -1.28 0.50 -1.45 0.55 -1.62 0.60 -1.80 0.65 -1.98 0.70 -2.18 0.75 -2.37 0.80 -2.58 0.85 -2.79 0.90 -3.00 0.95 -3.25 1.00 -3. ...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 Green Plants as Organisms 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 Green Plants as Organisms essays

  1. Peer reviewed

    Osmosis in potato and apple

    3 star(s)

    Also, in the preliminary I used 1 chip of each plant tissue for each concentration, so I had all together 4 results for each plant tissue. If I was to have the same amount of result for my experiment, the conclusion I would come to would not be reliable.

  2. Determination of the water potential of potato tissue by a gravimetric method.

    I would do the experiment along the 0.2M to 0.4M region with a difference of 0.05M so I can get a very accurate account of exactly at what molarity the mass change is zero. I would also do a lot of repeat experiment s to average out any errors and to make sure I get concordant results.

  1. What effect does the sucrose concentration have on osmosis?

    The concentrations will vary by: 5ml in each test tube: Experiment No. Sucrose Amount (ml) Distilled Water Amount (ml) 1. 20 0 2. 15 05 3. 10 10 4. 5 15 5. 0 20 3. I will add the different volumes of sucrose to water into different test tubes. 4.

  2. The effect that different concentrations of salt solution in the water has on strips ...

    These are just a few factors that could have caused a rise at the end of my graph. Improvements could have been made to the method, one would have been taking a wider range of molarities e.g. ) 0.0 M, 0.1 M, 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M, 0.7 M, etc.

  1. Investigate the cell sap concentration of solute in a potato chip using osmosis and ...

    the duration of the experiment and all the equipment used will be kept the same. It is predicted that the chips in 0% solute concentration will gain in weight by roughly 10% - 15% estimated by comparing the two lines of best fit from the predicted graph and the pre-test graph.

  2. To investigate the effects of using different concentration of Sucrose solutions in Osmosis with ...

    * When the solution is very weak (i.e. not much Sucrose) then the cucumber might still gain mass depending on how high the concentration is inside the cucumber. * As the concentration increases, the loss of water from the cells will increase. This will be shown by a change in mass.

  1. Discuss the various adaptations of vertebrates that enable them to live in marine conditions.

    It is important to note here that the senses are only as complex as they need be, see below for an example. Vision is the main form of perception on land but it is usually not the main one in water.

  2. Free essay

    Investigation osmosis in potato cells

    The weight and length are being measured in this investigation. The mass of each chip will be measured before and after so that more results can be obtained and to see if osmosis has occurred. Five potato chips will be placed in each of the five test tubes.

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