Sanghoon Lee<br />IB Biology SL Pd. 2<br />Mr. Harned<br />October 4, 2010<br />Rate of Diffusion Affected by the Change o...
바오 랩
바오 랩
바오 랩
바오 랩
바오 랩
바오 랩
바오 랩
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바오 랩

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바오 랩

  1. 1. Sanghoon Lee<br />IB Biology SL Pd. 2<br />Mr. Harned<br />October 4, 2010<br />Rate of Diffusion Affected by the Change of Temperature<br />Introduction<br />When red dye chemicals are released in a colorless solvent, they spread out gradually until the color of the solution turns into red. This is an example of diffusion. Diffusion is the movement of materials from areas of high concentration to areas of low concentration until equilibrium is reached. <br />Osmosis is a special case of diffusion. It is the diffusion of water across a semipermeable membrane. Osmosis depends on how much water (%) there is on each side of the semipermeable membrane. The difference occurs when there are different amounts of solutes in the water on each side.<br />When a cell is placed into a solution, the solution can have more solutes, less solutes, or equal solutes as compared to the cell. When the solution has more solutes, the solution is said to be hypertonic. The cell shrinks in hypertonic solution. When the solution has less solute less solute but more water, it is called hypotonic. The cell expands in hypotonic solution. When the solution has equal solute with the cell, it is defined as isotonic. The cell stays without change in isotonic solution.<br />The rate of diffusion is unstable and various, since many different factors including size, shape, concentration, and temperature affect diffusion directly or indirectly. In this research, the effect of temperature on the rate of diffusion will be investigated. Therefore, other factors besides temperature are controlled equally on each trial.<br />Research Question<br />How does the temperature in solution affect the rate of diffusion?<br />Hypothesis<br />If the temperature of the solution is high, then the rate of diffusion will increase.<br />Variables<br />VariableTypeHowTemperatureIndependentBy using ices and heating deviceRate of diffusionDependentBy comparing the before and after mass of the potato in percentageSurface areaControlledBy using cork borer and ruler to measure and cut the potatoShapeControlledBy using cork borer and ruler% saltControlledBy using one big beaker to make the salt solution, and then pouring it into each test tubeTimeControlledBy limiting the time to 5 minutes per trialFirmness and humidity of the potatoControlledBy using one potato for every piece of samplesshape of each cup holding the potatoControlledBy using the same test tubeAmount of water in each test tubeControlledBy limiting the amount of water as 10 ml in each tube<br />Materials<br />One potato<br />Cork borer<br />Ruler<br />Knife<br />Electronic scale<br />Beaker big enough to contain 120mL of salt solution<br />Plain water<br />Salt<br />Cylinder with measures<br />12 test tubes<br />Test tube holder<br />Ice<br />Heating device<br />Thermometer<br />Tissues<br />Time watch<br />Procedure<br />Use cork borer to dig potato samples from one potato.<br />Use knife and ruler to cut 12 pieces of potato samples with same lengths and shapes.<br />Measure each piece on an electronic scale.<br />Record each mass of each piece.<br />Fill one beaker with plain water<br />Pour the salt in the water to make 5% salt solution. (5% salt solution is consisted of 5% salt and 95% water, not 5% salt and 100% water. Therefore, the mass of the salt should be controlled as 595 of the mass of water.)<br />Pour the solution in 12 test tubes. (10 ml each)<br />Put four potato samples in four different tubes.<br />Place those tubes on a test tube holder and locate it on the table with normal room temperature. (Avoid places where air conditioner is directly blowing)<br />Wait for 5 minutes.<br />Take out the potato samples and dry them carefully with tissues.<br />Measure the mass of each sample and record.<br />Pour plain water in a new beaker and put ices.<br />Locate test tubes with 10 ml salt solutions in the beaker<br />Wait until the temperature of the salt solutions become about 3℃.<br />Put the potato samples in each tube<br />Wait for 5 minutes<br />Take out the potato samples and dry them carefully with tissues.<br />Measure the mass of each sample and record.<br />Pour plain water in a new beaker.<br />Locate test tubes with 10 ml salt solutions in the beaker<br />Locate the beaker inside the heating device.<br />Wait until the temperature of the salt solutions become about 53℃.<br />Put the potato samples in each tube<br />Wait for 5 minutes<br />Take out the potato samples and dry them carefully with tissues.<br />Measure the mass of each sample and record.<br />Data Collection and Processing<br />TrialsTemp(℃±.1)Mass of the potato (g±.01) before & after the trialTrial 1Trial 2Trial 3Trial 422.2Initial mass (g)1.081.111.101.08Final mass (g)0.930.970.980.9352.8Initial mass (g)1.081.131.131.07Final mass (g)0.830.920.930.883.1Initial mass (g)1.121.121.091.09Final mass (g)1.021.001.010.98<br />Table 1: Raw data of the mass of the potato samples (before & after the experiment)<br />Chart 1: The rate of decrease(%) in mass of potato samples in each trial according to the temperature(℃).<br />According to the chart, the rate of decrease in mass of the potato samples is highest in the warm temperature, lowest in the cool temperature, and medium in the room temperature. This information is interpreted as; the diffusion is most active in the high temperature, and relatively inactive in low temperature. <br />Graph 1: The rate of diffusion (%) in potato according to the change of temperature(℃) including uncertainty rate.<br />According to the graph, the linear line nearly matches the data line. Since the slope of the line is positive(+0.1849), it can be stated that the correlation between two aspects (percentage and temperature) is positive. Therefore, it is predictable from this graph that as the temperature of the solution increases, the rate of diffusion also increases.<br />Sample Calculations<br />The percentage of decrease in potato’s mass in each trial<br />= (1-Final massInitial mass) × 100<br />Ex) (1-0.931.08) × 100 = 13.9%<br />Arithmetic mean of the rate of diffusion(%) according to the temperature(℃)<br />= (Sum of the % diffusion rates of each trial according to temperature of) / 4<br />Ex) (13.8 + 12.6 + 10.9 + 13.9) / 4 = 12.8<br />Conclusion<br />Hypothesis was supported. As the temperature of the solution got higher, the rate of diffusion increased. And the rate of diffusion decreased as the temperature of the solution got lower. The average percentage of diffusion in high temperature was 19.0%, while the average percentage of diffusion in low temperature was only 9.9. Therefore, it was concluded that there is a positive correlation between the temperature rate and the diffusion rate. <br />Increase in temperature increases the molecules’ speed (kinetic energy). Since diffusion is a passive movement of molecules, this faster movement of molecules translates into quicker diffusion. In other words, the molecules spread from high to low concentration more rapidly. <br />Evaluation<br />In general, the results of the experiment appeared to be significant, with clear differences according to the change of temperature. <br />However, there were critical limits in the experiment as well. First of all, the range of temperature was severely limited. The lowest degree of temperature measured in the experiment was 3.1℃, which is relatively high compared to the absolute zero, which is-273.16℃. The highest temperature was 52.8℃, which is relatively low compared to the boiling degree of water, 100℃. The results may have appeared to be different if those lowest and highest temperatures had been measured. <br />Another limit of the data was found from the process of the experiment. After the potato samples were taken out from the test tube, they had to be dried gently with the tissues. However, some of the samples were dried with strong rubs with the tissues, which may have resulted in errors in the data. The problem was that some of the samples were extra-dried while others were not dried enough. The mass of the extra-dried samples may have appeared lower than real, because the tissues had absorbed most of their water within. <br />This limit can be improved by naturally drying the potato samples in a given period of time rather than depending on human hands, which are relatively inaccurate. The potato samples would be controlled more easily and accurately by simply waiting for a short period time until they naturally dry enough.<br />The limit in the range of temperature can be improved by using freezer and alcohol lamp in a sealed room, where temperature can be measured in higher range without the risk of losing heat through the air.<br />

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