The volume of oxygen gas produced in a certain time Essay Example for Free

The volume of oxygen gas produced in a certain time Essay I will also being doing 3 repeats of each reaction in order to get a set of more reliable and accurate results because they results will vary. The reactions will be as follows: 1) 5 cm3 of H2O2 and 5 cm3 of yeast (100% of yeast) 2) 5 cm3 of H2O2, 4 cm3 of yeast and 1 cm3 of water (80% of yeast) 3) 5 cm3 of H2O2, 3 cm3 of yeast and 2 cm3 of water (60% of yeast) 4) 5 cm3 of H2O2, 2 cm3 of yeast and 3 cm3 of water (40% of yeast) 5) 5 cm3 of H2O2, 1 cm3 of yeast and 4 cm3 of water (20% of yeast) 6) 5 cm3 of H2O2 and 5 cm3 of water (0% of yeast) (Control of experiment). This is how the experiment will be carried out after setting up the apparatus: 1) Use syringe to add y cm3 of yeast into the conical flask. 2) Use a second syringe to add the x cm3 of water depending on how much yeast is going to be used. (Look at the list above) Make sure volume of gas in syringe is still 0 cm3. 3) Use a third syringe to put 5 cm3 of H2O2 into the conical flask and use the other hand to start the timer on the stop watch at the same time as the H2O2 is added. (Leave syringe in the tube so it stays air tight). 4) Note the volume of gas given off in cm3 when the timer reaches 15 seconds. 5) Rinse conical flask and then repeat with 80%, 60%, 40%, 20%, 0% of yeast (use the list of reactions above for volumes) 6) Repeat each reaction 3 times Safety Always wear lab coats, glasses and gloves because H2O2 is a substance that very corrosive and can cause lots of damage to the skin and it can also blind if there is contact with the eyes. If there are any spillages onto the skin or it seems you have a burning sensation on your skin, rinse immediately and inform teacher. If there is any contact between eyes and H2O2 inform the teacher quickly and rinse until the teacher attends to you. Variables and Fair Test In this experiment I will have to keep certain variable the same in order to get accurate and reliable results. In total there are 7 variables in this experiment and they are the following:   pH   Temperature   Enzymes Concentration   Substrate Concentration Total volume   Time   Oxygen produced Out of all of these variables there is one Dependent Variable, this is oxygen produced variable because this is what I am measuring by altering one of the other variables. Apart from the dependent variable all of the rest are independent variables and so therefore any one of these could alter the dependent variable giving me unreliable results. Therefore I will now explain what these variables can do and what to do with them in order to keep them constant. The variable pH is important because if the pH of the solution in which the enzyme is present is too low or too high the enzyme will not function properly because the pH will damage the shape of the enzyme and the shape of the active site making it so that the substrate molecule will not be able to fit into the active site, thus not allowing the enzyme to break it down. This will mean that the rate of oxygen produced will slow down. In my experiment I will keep the pH about 7 because this is Catalases optimum pH and this maintaining of pH is not difficult because all the substance that I am going to use will be neutral pH. This damaging of the enzyme is called Denaturing and is permanent.. Enzymes as I said earlier were proteins and this is why they can be denatured very easily. Temperature is important because it is able to increase the rate of oxygen produced and also decrease the rate of oxygen produced. I know it can increase the reaction rate because if there is a higher temperature the particles would have more kinetic energy and therefore there would be a faster rate of collisions and a higher % of successful collisions because since the particles would have more energy it would be easier to reach the activation energy and so more reactions (this would be the opposite if it was a lower temperature). The rate of oxygen produced could be decreased by the fact that proteins can easily be damaged by heat so if there is a high temperature the enzyme can be denatured and if there is a low temperature they can become inactive. My experiment will be done at room temperature. Enzyme concentration is not a problem because this is the variable which I am changing to find out the effects it has on the dependent variable. Substrate concentration can alter my results in two ways. One is that it will make my results quicker than they should be, if I put a higher volume in some and lower in others because from Collision Theory I have learnt that if there is a higher concentration of a substance in a solution it will have more collision which means more reactions and therefore this will make my results quicker than if I used a lower concentration of it. I can solve this problem by using the same volume of H2O2 in all my reactions. The second way that substrate concentration can affect my results is that it can level off the rate of oxygen made, if all the substrate is catalysed within my time range. I can solve this problem by simply using excess substrate but at the same time I will still have to keep the volume the same because of the problem I discussed earlier. Total volume must also be kept the same because otherwise the experiment would be unfair due to collision theory. This is because if the numbers of particles are changed, the number of collisions would be changed and therefore this means the number of reactions would change leading to a different amount of gas produced in my experiment. I can solve this by adding water when I use a smaller amount of enzyme. Time is another one of the variable that must be kept the same because if not the reaction would have more or less time to react and so producing different volumes of gas. I can solve this by always letting the reaction go on for the same amount of time; this will be 15 seconds in my experiments.