An Investigation to see how water with different concentrations of sugar affects the weight of potato chips
...not be accurate. „h Permeability of potato: we will use the same potato, because the thickness of membranes differ between potatoes „h How much water the potato contains: we will use the same potato, as water concentrations will differ between potatoes. „h Volume of solution: 10mls of solution will be placed in each test tube. This will be measured using syringes rather than measuring cylinders because it is far more accurate. Hypothesis When the potato chip is in pure distilled water it will gain weight because there are more free water molecules outside the partially permeable membrane than inside. Therefore more water molecules will diffuse into the potato chip causing a gain in mass and an increase in turgor because it will be filled with water. When the potato chip is in saturated sugar solution it will decrease in mass because water will move down its concentration gradient. Because the sugar solution is stronger than the cell sap of the potato cells, theses cells will lose water by osmosis. The cells will lose their turgor and the potato chip will become flabby. To keep the investigation fair, variables must be taken into consideration. The temperature must be kept constant because at different temperatures water can hold more sugar therefore the saturation of water will change. For example when it is warm molecules get more kinetic energy and osmosis quickens. However, if temperatures are too high the cell membrane will denature and osmosis will stop. It is also very important too use the same potato for all the potato chips because the permeability and the amount of water the potato contain differs between potatoes, and this could affect our results. Risk Assessment When carrying out the experiment you must be careful of breakage¡¦s when handling boiling tubes as they are made of glass. When using borers to cut your potato chips you must be careful, as they can be sharp. Also, the saturated sugar solution must be handled with care as it is very sticky and if you dropped it it would take a while to clean up. Apparatus „h 5 boiling tubes „h Potato „h 5 potato chips „h Borer „h Caliber „h Test tube rack „h Balance „h Syringe Diagram Method Five potato chips will be cut out of the same potato using a borer. The skin will be taken off because the skin is impermeable and water would not be able to enter the potato. The potato chips will be dried and cut accurately to the same length. They will be weighed on a balance and their mass will be recorded. Five test tubes will be filled with 10mls of water with different concentrations of sugar. „h Test tube 1 will have 100% saturated sugar solution „h Test tube 2 will have 75% saturated sugar solution „h Test tube 3 will have 50% saturated sugar solution „h Test tube 4 will have 25% saturated sugar solution „h Test tube 5 will have 0% saturated sugar solution ¡V pure distilled water A potato will be placed into each test tube and then left for thirty minutes so that osmosis can occur. The potato chips will then be taken out of the test tubes, dried and their mass re-weighed. The results will be recorded and from these a percentage mass change can be calculated and shown on a graph. The experiment will be repeated twice more so that we have have a reliable set of results, from which we can then take an average. The range that we have chosen is 100%, 75%, 50%, 25%, and 0% saturated sugar solution. As the range is quite broad it will provide us with a good set of results that show us how different concentrations of sugar affects osmosis in potatoes. We were able to decide how we carried out the experiment: 1. We could measure the length and breadth of the potato chips before and after osmosis occurred 2. We could weigh the mass of the potato chips before and after osmosis occurred. We chose to weigh the mass of the potato because it was easiest to do and provided more reliable results. Also, when carrying out our pilot study we found that by measuring the length of the potato chips, the difference was very small, so we decided not to use this. To change the concentration of water we used serial dilution. This is when 100% saturated sugar solution is taken and the percentage saturation required is filled using a syringe. For example, if you want a solution with 25% sugar, you would fill the syringe with 2.5mls saturated sugar solution and 7.5mls distilled water, so that the volume of each solution is 10mls. To keep the experiment fair: „h The same potato will be used for each of the potato chips. The same borer will be used to cut the potato chips so that they all have the same surface area. „h The temperature will be kept constant at room temperature, so that osmosis will not speed up or slow down. Results Mass change: Concentration of saturated sugar solution % 1st readings 2nd readings 3rd readings Before g After g Before g After g Before g After g 100 3.95 3.53 3.43 3.23 2.53 2.31 75 4.05 3.78 3.38 3.32 2.69 2.60 50 3.85 3.67 3.27 3.15 2.72 2.69 25 4.11 4.02 3.33 3.32 2.50 2.47 0 3.99 4.18 3.38 3.59 2.61 3.13 To convert my results into the percentage mass change I used this equation: FINAL MASS ¡V INITIAL MASS * 100 =¡K... % INITIAL MASS Percentage Mass Change: Concentration of saturated sugar solution % 1st reading 2nd reading 3rd reading Average 100 -8.6 -5.7 -8.0 -7.4 75 -6.6 -5.0 -6.1 -5.9 50 -4.6 -3.7 -3.1 -3.8 25 -2.2 -0.3 -1.2 -1.2 0 4.8 6.2 19.9 10.3 Analysis From my result tables and the graph, you can see when the concentration of sugar solution is low, the potatoes mass increases. This happens because free water molecules diffuse through the partially permeable membrane into the potato chip, therefore keeping the concentration of sugar and water equal. When the concentration of sugar solu...