30 Minutes The Potato Piece Needs example essay topic

GCSE Biology: Osmosis in a PotatoAimTo investigate the effect of placing a piece of potato in a given strength of sugar solution. Prediction predict that, as the solution becomes more concentrated the more the cell will shrink, as the water, of higher concentration inside the potato cells, flows down a concentration gradient into the solution, which has a lower concentration of water molecules. If we say that the percentage change when the potato is placed in the 1 M solution is x%. I predict that when the solution is 0.5 M the percentage change will be 0.5 x%, and when the solution is 0.25 M strength I hypothesis e the change will be 0.25 x%. Variables Description: Dependant Variables The dependant variable is plotted on the y-axis.

In this experiment this is the change of mass of the potato when it is placed in different strengths of sugar solution. Variables Description: Independant Variables The in dependant variable is plotted on the x axis and is what you choose to change in the experiment. In this experiment it is the strength of the sugar solution. Variables Description: Constant Variables These stay the same all the way through the experiment and are the fair test rules. In this experiment that are that the amount of sugar solution used must always me 10.0 ml. This is to be placed into the test tube.

The solution needs to always be at the same temperature. We will make sure that all experiments are at 20 degrees centigrade before we start the experiment. The size of the potato sample that we place into the solution also needs to be kept constant. A mass of 2.5-2.6 g is sensible. The diameter is fixed as the potato cork borer always measures to the exact same measurement. We also needs to make sure that the potato is left in the solution for the same time, 30: 00 minutes.

Equipment Potato o Standard Sugar Solution o Wash Bottle o Test Tubes and Test Tube Rack o Cork Borer o Scalpel o Cutting Board o Scales accurate to 2. d. p o 10 ml Syringe o Paper towels o Ruler o Stop Watch Method 1. Firstly, the cork borer needs to be used to cut out a piece of potato at least 4 cm in length. This allows room for trimming off untidy edges. 2.3. On the cutting board the cylindrical piece of potato needs to be cut to 35 mm. Using a ruler, measure this as accurately as possible and cut the potato to 35 mm in length using a scalpel. 4.

Using the scaled weigh the potato to 2. d. p. and record the weight. 5. The test tube rack and test tubes need to be assembles. Fill a syringe with exactly 10 ml or sugar solution (strength 1 M) and empty into a test tube.

6. Now the timing device needs to be reset and readied. An extra pair of hands to aid in the timing may be useful. Ths potato piece can now be placed into the test tube containing 10 mb of 1 M sugar solution. 7.

As the potato piece is placed in the test tube, the timer should be started. After 30 minutes the potato piece needs to be removed from the test tube. 8. Place the potato piece once again on the scales and work out the percentage change. 9. Repeat this experiment for 0.5, 0.25 and 0.125 concentration solutions of sugar solution.

Results Mass of Chip at... This disagrees with my prediction. My prediction hypothesis ed that there would be a difference and that half the solution concentration would result in half the percentage change in mass of potato. There was one anomalous result (0.125, 16) appeared a 16% change, whereas all the other results appeared as a 12% change.

No obvious factors can be found for this result, the piece was 2.5 g as many of the others were, yet it increased to 2.9 rather than 2.9 as had the others. As the scales were only correct to 1. d. p. it is possible that the amount was very near to the others and yet the measuring was less accurate and the rounding and inaccuracy in measurements caused this result. Evaluation The results from this experiment do not agree with my prediction. To get accurate results more precise equipment needs to be used and to be repeated many more times. The test was as fair as it could be made by the imposed constraints. These constraints were factors such as time, and availability of equipment meaning there was not enough time for each experiment to be properly completed.

Each potato piece was only got 15 minutes in the solution, whereas 30 would have been more preferable. This could partly explain why the results did not support the prediction. The dependant variable, the change in mass of the potato could not be measure to a satisfactory degree of accuracy because we were using small test tubes we require more sensitive equipment that if the experiment were being performed on a larger scale. Unfortunately this was unavailable and so we could only measure the masses to 1. d. p. The solution strength could also have been measured more accurately if syringes had been available instead of measuring cylinders it would have made the solutions more accurate as measuring 0.0625 ml with the available equipment was near impossible. This along with weighing the mass of the potato piece were the two biggest sources of possible errors with the experiment.

If the experiment were to be performed again, more accurate equipment as describes above would be needed. The experiment would need to be tested for ratio's that are equally spread and with a smaller gap between testing values.