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The temperature should be kept at the same throughout the experiment to create a set of fair and even results. The volume of Hydrogen peroxide must be kept the same otherwise the alginate balls would travel different distances. The shape of the measuring cylinder must be kept the same otherwise the alginate balls would travel different distances. The size of the yeast beads must be kept the same. The height I drop the beads at must remain the same otherwise the distance that the bead has to travel will be faster for different beads. Independent Variable:
During the experiment, I changed the concentration of both hydrogen peroxide and water. Concentration of Hydrogen Peroxide (%) Concentration of Water (%) Dependant Variable: I measured the time it took for the bead, after being dropped into the hydrogen peroxide and water solution, to sink to the bottom of the test tube and rise again to the top. The bead rises due to the production of Oxygen (O2) bubbles surrounding the bead. Apparatus: Diagrams: Making the beads Timing the rising of the beads List: Alginate Water.
First of all I placed 3ml of alginate preparation into a small beaker. I then added 3ml of well stirred yeast suspension. This means that the yeast-alginate solution was 1:2. After that I mixed the contents of the beaker very thoroughly using a glass rod. In a further beaker, I placed enough calcium chloride solution to give a depth of 3 ml.
Using the glass rod, by holding it level with the rim of the beaker, I was able to drop some of the yeast-alginate mixture into the calcium chloride solution. Following that I produced a bead of 5ml which lied at the bottom of the beaker. I stirred the yeast-alginate mixture continuously with the glass rod, then I repeated this procedure to produce about 32 beads. I examined the beads that I made. I then removed and discarded any which were obviously different in size, distorted in shape, or which floated. The beads were picked up with a pair of tweezers. Method of the timing of the beads:
First of all I set up the apparatus shown in the second diagram. I then drop each bead in to the hydrogen peroxide and water solution (10ml). As soon as the bead is dropped from the tweezers I start the stop watch and stop it again when the bead reaches the surface. I will repeat each experiment 4 times and at 10 different concentrations of hydrogen peroxide and water. Each time, I will change the concentration of the solution by 10%. Prediction I predict that if I halve the concentration of Hydrogen Peroxide the time taken for the alginate balls to rise will double.
I think this because of the particle collision theory, which states that if there are twice as many particles there is twice the probability that the particles will collide. Therefore if there are half as many there is half the probability that the particles will collide. Results Table Concentration of Hydrogen Peroxide (%) Concentration of Water (%)
Time (s) Conclusion/Analysis I think that my results turned out like I predicted in my prediction, but at the end of the results the alginate balls take longer than I predicted. By looking at the graph I have drawn you can see that if you take a point on the X axis (e. g. 40) then follow it along to the Y axis and read the result and then do the same twice as far up the X axis (e.g. 80) the number you get on the Y axis should be double the previous number.
I have highlighted this on the graph to show that the results are correct to my prediction. The results turned out this way because of the particle collision theory that states that if there are twice as many particles there is twice the probability that the particles will collide. Therefore if there are half as many there is half the probability that the particles will collide. I could make this experiment better by making more accurate measurements.
For example if I measured every alginate ball and weighed them to make sure all the balls are the same the results are likely to be more accurate. Also if I repeated the results many more times I would get a more accurate set of results. Another important factor to consider is that Human accuracy in measuring the time is not terribly accurate. You could make your results more accurate by using light gates to sense the alginate balls passing certain points (Top and bottom). By looking at my graph I think you can see that my results are good enough to support my conclusion.