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the effect of catalase concentration on the breakdown rate of h2o2

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enzyme coursework: the effect of catalase concentrations on the rate of break down of hydrogen peroxide sara de sousa scientific knowledge and understanding: A rate is a measure of change that occurs in a given time whilst a reaction is the interaction of substances undergoing chemical change. The velocity at which any mix of substances are transformed into a product/s in a given unit of time is the rate of reaction. The speed at which this modification occurs relies on two main factors; the amount of collisions between reacting particles and what portion of these collisions are successful in producing a change within the substances present. Reactions between chemical substances will only occur if the particles collide with enough energy to break their initial bonds. This initial energy is called the activation energy. Collision theory: In order to react, particles must collide with a force sufficient to overcome the activation energy. There are four methods of increasing the rate of a reaction, and all can be explained in terms of increasing the number of collisions between reacting particles; 1. Temperature: when the temperature is increased particles move faster as they have more kinetic energy, encouraged by the heat. The more rapidly particles are moving, the more collisions are going to occur. 2. Pressure (or concentration): the more concentrated a solution, the more particles of a reactant are present. The higher the number of particles present the higher the likelihood of collisions. 3. Surface area: if one of the reactants is a solid then breaking it up into smaller pieces will increase its surface area. This means that particles in the solution around it will have a larger area to work on, so there will be more collisions in a shorter time. If both reactants are dissolved in solution/in a liquid state, surface area does not pertain and they relate directly to pressure/concentration. 4. Catalysts: catalysts work by giving the reacting particles a surface to stick to, where they can bump into each other. ...read more.


As I have increased the concentration of each catalase solution constantly, by the same amount each time, I assume that the initial rate of reaction for each catalase concentration will increase by the same amount each time. I believe that the 55% concentration solution will occur just under half the speed of the 25% concentration and at just over a third of the speed during the 70% concentration. apparatus (and justifications): ? Distilled water; will be used to clean some of the apparatus and to compose the catalase solutions instead of normal tap water, because it has no impurities, which may affect the break down of H2O2, resulting in inaccurate results. ? Celery extracts; will be combined with the distilled water to make the different catalase solutions. ? Hydrogen peroxide; the difference in the rate of break down of H2O2, into water and oxygen, will be observed of different concentrations of catalase solutions. ? 3 10ml and 2 5ml syringes; 1 of the 10ml syringes will be used for the hydrogen peroxide, whilst one of each size is used for both the distilled water and the celery extracts. I will be using syringes rather than measuring cylinder because they are much more accurate in measuring liquids, and are still practical to use, as I will only be using relatively small amounts of each liquid. ? 3 50ml glass beakers; I will pour each of the different liquids into a different beaker, so that they can be 'sucked up' by the syringes. ? 6 25ml glass beakers; to hold each of the catalase solutions. ? Conical flask; the shape of the conical flask allows for the 'swirling' of the liquids which are in it. This is a very important feature, as the H2O2 will need to be stirred with the catalase solution in one way or another to ensure that the enzyme and substrate molecules are evenly dispersed, without any being lost in the process. ...read more.


I concluded that there was no need to carry out the experiment for less than 25% because it would happen too slowly to be bothered with. I decided to choose concentrations that had less of a difference, so that when it comes to plotting my graph I will be able to plot points closer together and get a more accurate line of best fit. During my preliminary investigations I only noted the volume of gas produced every 30 seconds, but found that it was difficult to see the progression, so I decided to shorten the time intervals to 15 seconds for the real experiment so that the difference between the amount of oxygen produced would be more evident. I decided to carry on each experiment for 3 1/2 minutes to end up with 14 results for each concentration. The more results are obtained the easier it is to plot a graph and draw in the line of beat fit. I shortened the time to 3 1/2 minutes from 5, which I did in my preliminary because the volume did not alter very much after 4 minutes and this way I would be able to carry out the same experiment more times, to give me a more accurate average result. safety: Of the apparatus being used some is made of glass, and therefore very fragile. Care must be taken to ensure that none of the apparatus is knocked over/falls and breaks, as the glass would shatter. In the event of any breakages, DO NOT TOUCH ANY BROKEN GLASS, but call the supervising teacher immediately. Hydrogen peroxide must also be handled with caution. It is a corrosive chemical; so a lab coat and goggles must be worn. If contact is made with the skin, wash immediately with soap and water. To reduce the risk of any spillages, the transfer of H2O2 to different vessels should be limited, such as in step 5 of the method where it is transferred from the beaker to the syringe straight to the conical flask. as-level biology coursework, enzyme concentration, sara de sousa ...read more.

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