The correctly sized key - Sample Essay

I am going to try and find out how varying the concentration of Hydrogen peroxide changes the time it takes for the yeast alginate ball to rise from the bottom of the test tube with different concentrations of Calcium Carbonate and Water. Normally the decomposition of hydrogen peroxide takes a long time, but the catalyse will speed up the reaction. Introduction: Catalyse breaks down the Hydrogen Peroxide into water and Oxygen. We are measuring the production of Oxygen because it is a visible reaction, whist Hydrogen and Water are both clear fluids, so it would be impossible to see the actual reaction occurring.

During the production of Oxygen, Oxygen sticks to the beads and cause them to rise to the surface. Enzymes are useful because they are catalyses and speed up the reaction. The basic mechanism by which enzymes catalyse chemical reactions begins with the binding of the substrate (or substrates) to the active site on the enzyme. The active site is the specific region of the enzyme which combines with the substrate. The specific action of an enzyme with a single substrate can be explained using a Lock and Key analogy. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).

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Theory of reaction rates that states that effective collisions between reactant molecules must occur in order for the reaction to occur. Increasing the concentration (in solution). Increasing the concentration of a substance in solution means that there will be more particles per dm3 of that substance. The more particles that there are, the more will collide per second, and so the rate of the reaction increases Activation energy: the minimum energy necessary to form an activated complex in a reaction. Pilot: Results: Concentration of Hydrogen Peroxide (%).

Concentration of Water (%) Time (s) Preliminary Trial 100 0 6. 43 50 50 37. 89 10 90 59. 63 For preliminary work, I set up the apparatus up as show in the diagrams and dripped the yeast-alginate beads into a beaker of Calcium chloride solution three times. I chose the two extremes and the middle amount of concentration of both water and hydrogen peroxide. I found that many of my beads floated when I used the yeast-alginate solution with a ratio 1:1. To prevent the beads from floating, I made the beads thicker by adding some extra alginate.

I concluded that for my actual experiment I will need a higher ratio of alginate to yeast (2:1) to prevent my beads from floating. Hypothesis: I hypothesise that as the concentration of water compared to hydrogen peroxide solution increases so will the rate at which the bead rises in the calcium chloride solution. This will happen 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.

Safety: Since the hydrogen peroxide solution is highly corrosive I must take into account the following things:  I must wear goggles at all times in case hydrogen peroxide splashes anywhere near my face.  I must wear a lab coat in case any hydrogen peroxide may spill on my clothes or skin  There must be a sink near by so if and hydrogen peroxide spills on my skin I can wash it off as quickly as possible.  There must be a mop or paper towels near by in case there is a spillage of the hydrogen peroxide solution.



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