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An Investigation to find the Water Potential of Plant Tissue

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An Investigation to find the Water Potential of Plant Tissue Benjamin Doughty Aim: To find the water potential of plant tissue by investigating the effects of varying concentrations of sugar solutions on the amount of osmotic activity between the solution and potato cylinders. Hypothesis: Osmosis is defined as the net movement of water from regions of high water potential to regions of low water potential. This movement must take place across a partially permeable membrane such as a cell wall, which lets smaller molecules such as water through but does not allow bigger molecules to pass through. The molecules will continue to diffuse until the area in which the molecules are found reaches a state of equilibrium, meaning that the molecules are randomly distributed throughout an object, with no area having a higher or lower concentration than any other. Prediction: Pure Water has the highest water potential (zero). For this particular investigation I think that the lower the concentration of the sugar solution in the test tube the larger the mass of the potato will be. This is because the water molecules pass from an area of high sugar concentration, i.e. in the water itself, to an area of low concentration, i.e. ...read more.


2.07 0.485436893 0.50m: 1st attempt 1.69 1.62 -4.142011834 2nd attempt 1.78 1.67 -6.179775281 0.75: 1st attempt 1.76 1.6 -9.090909091 2nd attempt 1.71 1.56 -8.771929825 1.0m: 1st attempt 1.74 1.59 -8.620689655 2nd attempt 1.4 1.25 -10.71428571 Percentage change Concentration Average % change 0.00m 4.94128412 0.25m -2.11022273 0.5m -5.16089356 0.75m -8.93141946 1.0m -9.66748768 These preliminary results gives me the overall impression of the change in mass, gain and loss when placing potato chips in varying concentrations of sucrose solution. To carry out this investigation I will use the following apparatus: * Sucrose Solutions * 2 different sized measuring cylinders (10ml and 25ml) - More accuracy * Ceramic Tile - To cut potato on using scalpel * Ruler - To Measure potato chips * Scalpel - To cut potato into appropriate sizes * Forceps - to hold the potato chips * Stopwatch - to measure the time the experiment is taking accurately * 10 boiling tubes - to place potatoes and sucrose solutions in * A boiling tube rack - to hold boiling tubes * Potato borer - To cut pieces from potato - more accurate than cutting * Scales - To measure mass of the potatoes (g) ...read more.


I will then write all results in a table like this: All length and masses in this table are averages taken from three different potato chips per solution. Molarity of Sucrose Solution Starting mass Starting Length Mass 10min Length 10min Mass 20min Length 20min Final Mass Final Length 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 To Make this a fair test, all Variables (except the independent variable), must be kept constant to allow for a fair test. Some of these are: * The length, mass, diameter of the potato tubes. * The volume of solutions used, giving consistency * The temperature, increasing temperatures lead to an increase in kinetic energy and thereby the rate of diffusion will increase. * The time the potato tubes are left in their solutions. More exposure equals more osmosis taking place. * To follow consistency, the same apparatus used. * It is best not to touch the potato to avoid contact with cell surface membranes, so I will use forceps. When working on an experiment, it is easy forget how to handle things safely and conduct yourself in a safe manor. * Unused surfaces to be kept clear during the experiment. * Wash your hands before and after using the lab * Proceed with care when working with glassware and electrical light sources. * Always take care when handling chemicals. ...read more.

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*** Plan and trial experiment only. The mark has only been awarded for the planning section as no results, conclusion or evaluation have been included. The candidate has planned and carried out a trial experiment and achieved some sound results. To improve more care needs to be taken to ensure all experimental details are included and that tables are recorded clearly with fully labeled headings. There is also some confusion in the relevant background theory which could have been clarified with the inclusion of clear annotated diagrams and some relevant selected material from textbooks or websites. These should be added as references at the end of the report.

Marked by teacher Stevie Fleming 29/05/2013

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