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Investigating the factors that affect the rate of hydrogen peroxide.

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Investigating the factors that affect the rate of hydrogen peroxide Hydrogen peroxide is found in the body as a waste product of respiration, it is broken down by the enzyme catalase, which is found in all cells of the body. The enzyme is present to prevent the build of hydrogen peroxide, which is toxic; it acts a catalyst to speed up the break down of hydrogen peroxide to water and oxygen: One molecule of catalase is able to break down 40,000 molecules of hydrogen peroxide per second. The kinetic theory of matter summarizes al of the ideas about the movement of particles in solids, liquids and gases, the main points concerning liquids (the state of hydrogen peroxide) are summarizes below: * All matter is composed of tiny, insoluble particles. * In liquids, the particles are slightly further apart than in solids and possess larger amounts o f energy. Thus they are able to overcome the forces between each other to some extent and can mover freely around each other whilst in close proximity. The liquid particles have vibrational and rotational and translational motion. * An increase in temperature causes an increase in the average kinetic energy of particles. The kinetic energy is manifested as vibrational, rotational, and translational energy in liquids. According to the Brownian motion, particles in a liquid are moving around constantly colliding with each other. In reactions, when the molecules collide, and they collide with enough force (activation energy) a reaction occurs. An enzyme acts as a catalyst speeding up the reaction. Under normal conditions, hydrogen peroxide will take very long to break down to water and oxygen. And catalase speeds up the reaction in two ways: * It brings the molecules closer together, increasing the chance of a collision. Therefore more collisions would occur per unit of time, increasing the chance of a collision. Therefore more collisions would occur per unit of time, and hence the rate of reaction increases. ...read more.


The timer will still start when the chips are dropped into the boiling tubes. However, this time, the gas released from the reaction will be bubbled through water into the measuring cylinder. Oxygen is very insoluble in water and it will displace water in the measuring cylinder. As it is less dense than water it will rise to the top, and the volume of gas can be measured and the results can be recorded. To make sure the experiment is a fair test, all of the potato chips will be measured to 30 mm and as the chips are cut from the same chipper they will be of the same diameter. If the diameters or lengths were not the same, the number of potato cells will not be the same, and thus the concentration of enzymes would not be the same and therefore the experiment would not be fair. The phosphate buffer is added to make sure that the pH inside the boiling tubes will be constant. Any changes in the pH will affect the enzymes and would therefore disrupt the investigation. In addition to the devices set up in the previous method to make sure that investigation is a fair test, the reaction will also be put into a water bath to keep the temperature of the reaction constant. The temperature is the average speed at which the particles move, the higher the temperature, the greater the speed. The particles of reactant collide and release enough energy a reaction occurs. Particles moving at greater speed would have a greater chance of colliding, but also, as they are moving at a greater speed, they have greater kinetic energy. This increases the number of successful collisions per unit of time, thus increases the rate of reaction. That is why it is very important to keep the temperature of the reaction constant. The independent variable in this experiment will be the number of potato chips used, and the dependent variable will be the height of the froth produced. ...read more.


There were 10 readings in all for each of the enzyme concentrations to draw the graphs. There were enough results to draw accurately a line of best fit, these lines of best fit, were sufficient in pointing out a conclusion. As there were 2sets of results, there were enough correct results collected to draw a conclusion. There is one extension to the investigation in particular that could be carried out. As only the straight-line part of the graph of the relationship between the rate of reaction and the concentration of enzymes, an extension would be to investigate the point at which the graphs gradient begins to decrease and gradually decreases so that increasing the concentration gradient of enzymes would not have increased the rate of reaction. This would mean increasing the number of chips up to 75 chips. But the scale of the investigation would have to increase as the boiling tube would not be able to take 50 potato chips. Or instead of adding potato chips, the enzyme catalase itself could be added. This would be a better way of measuring the amount of catalase breaking down the hydrogen peroxide. The gap of chips would continue to be 2 chips, starting from 1 chip to 3 chips to 5 chips and etc. I think continuing to 75 chips would usually allow me to obtain results that would allow me to find out at what enzyme concentration Point X on the graph below will be reached. However, as time was limited for this investigation, it was not possible to carry on the experiment to that extent. And the graph plotting the rate pf reaction against the concentration of enzymes was still a straight line. This would involve using the second method of the investigation, but with the improvements that has already been suggested. There would be more repetitions of the investigations, and the amount of hydrogen peroxide be measured as well as the amount of oxygen released from the reaction. The reasons for these modifications to the method have already been given. Peter Cui GCSE Biology 1 ...read more.

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