Investigating the effect of Sucrose Concentration on the Rate of Osmosis in Potato Chips.

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G.C.S.E Science:

Investigating the effect of Sucrose Concentration on the Rate of Osmosis in Potato Chips

Sophie Chapman

25th March 2003 

Aim:

 

I shall carry out a sequence of independent experiments in order to investigate how the rate of osmosis in a potato chip is affected when the concentration of sucrose solution is varied.

Apparatus: 

                   

                   300ml Sucrose concentration

                   300ml Distilled Water

                   2 x 100ml beaker

                   1 x 100ml Measuring Cylinder

                   1 x Potatoes

                   1 x Forceps (Tweezers)

                   1 x Scalpel

                   Chipper

                   12 x Polystyrene Cups

                   1 x Stop - clock

                   Tissues

                   12 x Sticky Labels

                   1 x Pen

                   1 x Calculator

                   1 x Ruler (measuring mm)

                   1 x Balance

                   1 x Polythene Food Bag

                   Cardboard

                   

Apparatus Justification:

To complete the experiment, I need 300ml distilled water and 300ml sucrose concentration as I intend to carry out 12 tests (using 6 different volumes but each shall be repeated twice) each using a 100ml of liquid whether it be pure water, pure sucrose concentration or a solution containing both. I will detail about the exact volumes of water and sucrose concentration that I want to use in each experiment, in the written procedure. I shall use varied amounts of sucrose solution for each test in order to adjust the concentration – a solution containing more sucrose has a greater concentration than a solution containing less sucrose solution. It is essential that the concentrations be varied throughout the investigation for I am analysing the effect of sucrose concentration upon the rate of osmosis in potato chips.

   Distilled water is required to reduce the concentration of the sucrose solution. I shall use distilled water as opposed to tap water because it is de – ionised and contains fewer impurities therefore is unlikely to contaminate the experiment and affect the results achieved.

  I have chosen to use a measuring cylinder that can measure out 100ml of liquid without having to constantly refill a smaller measuring cylinder (such as a 50ml one) to obtain a given amount of liquid that exceeds the capacity of the measuring cylinder used e.g. 60ml. The constant refilling of a small measuring cylinder to gain a larger amount increases the chance of error, as spillage is more probable.

    There is no need to use a 200ml to measure either the distilled water or the sucrose concentration as the maximum amount of each that I plan to use is only 100ml, a measuring cylinder of the same amount is sufficient. A measuring cylinder that does not exceed 10ml is not suitable neither to measure out bigger amounts of either water or sucrose concentration as there is more chance of spillage. Consequently there is more chance of obtaining inaccurate results because the initial amounts used to make the solution would be wrong.  Using a measuring cylinder that is 10 times smaller (such as 10ml) than the largest amount needed (100ml) not only creates a chance of causing inaccurate results but is also a waste of time when there are measuring cylinders that can capacitate for the maximum quantity, available.

   I shall use two 100ml beakers. Approximate volumes of sucrose concentration will be poured into one of these and transferred into the measuring cylinder. This is because one is likely to make fewer mistakes using this method rather than pouring the sucrose directly from a large, heavy container where it is likely to spill and possibly affect other components in the experiment. The other beaker will be used to transfer water into the measuring cylinder for the same reasons.

  I will use one potato because I want to obtain results that are accurate. Using the same potato throughout the experiment means that each potato should share the same genetic make – up whereas two different potatoes are likely to have dissimilar genetic features. Two potatoes might have dissimilar sucrose concentrations that could distort the results and prevent one from identifying how the concentration of sucrose solution affects the rate of osmosis in potato chips.

    I will cut the exact lengths of the potato chips using a scalpel. I shall also use a pair of forceps to pick up and move the potato chips. Forceps are better to use as opposed to fingers because one might have germs on their hands that could contaminate the experiments or excess moisture that would distort the mass shown on the balance when each potato chip is weighed.

   I shall use a chipper. This is a piece of apparatus that cuts potatoes fairly accurately. Unlike the inaccuracies when using a knife, the chipper ensures that each potato chip has the same cross – sectional area. There will still be errors due to the length at which the potato chips are cut and any inaccuracies in the lengths of the chips will be dependent on the accuracy of the human eye needed to judge the correct length at which they should be sliced. If the potato chips have roughly the same area, the results shouldn’t be drastically distorted.

   I shall use a ruler that measures mm as well as cm in order to measure the potato chips to the nearest degree of accuracy. Therefore when the results are obtained, they are not inaccurate due to a ruler that is not as precise as the one I intend to use. Accuracy throughout the experiment will improve the exactness of the results I find.

   The experiments will take place within 12 separate polystyrene cups and a stop – clock will be used to measure the time periods for which the chips are left immersed within the liquids and when they should be removed from the liquids and dried and weighed.

   I shall use tissues to dry the potato chips when they are removed from the liquids in order to remove excess moisture on the chips from the fluids that they have been placed in. It is essential that the chips are dry so that the results are not distorted due to surplus water affecting the actual weight of the potato chips when they are weighed between intervals.

   Sticky labels are needed to label each cup (with a pen) where the experiments occur to prevent confusion and the wrong figures being recorded for an experiment that didn’t actually provide those results.

  I shall use a calculator to calculate the average weights using the results from both sets of experiments. A balance is essential to the experiment in order to weigh the potato chips before and after they are immersed in pure water or a solution containing sucrose concentration. When the potato chips for the second series of experiments are not in use, I shall store them in polythene food bags so that they don’t oxidise and affect the results.

Method:

  • Collect apparatus.
  • Label 6 polystyrene cups each with a different letter, i.e. 1, 2, 3, 4, 5, and 6.
  • Pour a random amount of distilled water from its larger beaker into a smaller 100ml beaker.
  • Measure 100ml of distilled water (taken from the 100ml beaker) using the 100ml measuring cylinder.
  • Pour this amount into cup 1. The concentration of sucrose in cup 1 is 0.0 mol/litre.
  • Pour a random amount of distilled water from its larger beaker into a smaller 100ml beaker.
  • Pour a random amount of sucrose concentration also from its larger beaker into another smaller 100ml beaker.
  • Measure 80ml of distilled water (taken from the 100ml beaker) using the 100ml measuring cylinder and pour into cup 2.
  • Rinse measuring cylinder and dry it off with tissues ensuring that there is no excess moisture inside before the next quantity is measured.
  • Measure 20ml of sucrose concentration (taken from the 100ml beaker) using the 100ml measuring cylinder.
  • Pour the amount measured into cup 2. The concentration of sucrose in cup 2 is 0.2 mol/litre. 
  • Repeat the stages above which are written in red ink replacing the bold, black, underlined quantities for the values of cups 3, 4, 5, and 6, recorded in the table below:

  • Set out the cups containing specific amounts of liquid as shown below:

  • Take potato, cut into smaller chips with exact cross –sectional areas using the chipper.
  • Select 6 of the potato chips and line them up next to each – other (as shown below). Place the other potato chips into the polystyrene food bag and ensure that it is airtight.
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  • N.B: When selecting suitable potato chips, choose those that are longer than 7cm so that they can be cut down to the exact length.

  • Using a ruler, measure 5cm across from the end highlighted by the red arrow above.
  • Using a pen, mark off 5cm on each potato chip.
  • Place ruler horizontally so that it joins the pen marks each showing 5cm, together.
  • Run the scalpel firmly along the ruler so that excess potato is severed from the chips that are now 5cm and will be used for the experiments.
  • ...

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***** This write up is extremely detailed and includes a thorough analysis using appropriate scientific language which demonstrates a clear understanding of concepts.