Experiment 1 Diffusion through a Liquid In this experiment you will observe the effect that different molecular weights have on the ability of dye to travel through a viscous medium Materials Red and Blue Dye Solutions Blue molecular weight 793 g mole Red molecular weight 496 g mole 1 Bottle Corn Syrup 1 9 cm Petri Dish top bottom halves Stopwatch Ruler 2 Micropipettes Tape Procedure 1 Use tape to secure one half either the bottom or the top half is fine of the petri dish over a ruler Make sure that you can read the measurement markings on the ruler through the petri dish The dish should be positioned with the open end of the dish facing upwards 2 Carefully fill the half of the petri dish with corn syrup until the entire surface is covered 3 Place a single drop of blue dye in the middle of the corn syrup Note the position where the dye fell by reading the location on ruler 4 Measure the diameter of the dye the distance it has traveled every ten seconds for a total of two minutes Record your data in Tables 1 and 2 5 Repeat Steps 1 4 using the red dye the second half of the petri dish and fresh corn syrup 2013 eScience Labs LLC All Rights Reserved Table 1 Rate of Diffusion in Corn Syrup Time sec Blue Dye Red Dye Time sec Blue Dye Red Dye 10 25 4 mm 25 4 mm 70 44 45 mm 50 8 mm 20 38 1 mm 31 75 mm 80 44 45 mm 57 15 mm 30 40 64 mm 31 75 mm 90 44 45 mm 57 15 mm 40 44 45 mm 44 45 mm 100 44 45 mm 63 5 mm 50 44 45 mm 44 45 mm 110 44 45 mm 63 5 mm 60 44 45 mm 50 8 mm 120 44 45 mm 63 5 mm Table 2 Speed of Diffusion of Different Molecular Weight Dyes Structure Molecular Weight Total Distance Traveled mm Speed of Diffusion mm hr Blue Dye 793g mol 44 45 mm 1 333 5mm hr Red Dye 496g mol 63 5 mm 1 905mm hr Multiply the total distance diffused by 30 to get the hourly diffusion rate Post Lab Questions 2013 eScience Labs LLC All Rights Reserved 1 Examine the plot below How well does it match the data you took in Table 2 Submit your own plot if necessary My data matches the plot below pretty well My red dye diffused faster and farther than the blue just like in the plot 2 Which dye diffused the fastest They both diffused about the same rate at the beginning but the red dye continued to diffuse and the blue stayed the same after about 50 seconds 3 Does the rate of diffusion correspond with the molecular weight of the dye Yes the dye with the smaller molecular weight diffused the fastest 4 Does the rate of diffusion change over time Why or why not Yes the rate of diffusion decreased over time The red dye kept diffusing but it was at a slower pace 2013 eScience Labs LLC All Rights Reserved
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