Introduction In this experiment I shall investigate how the enzyme concentration can affect the initial rate of reaction. I will measure the effect of the enzyme in 5 different concentrations against the controlled variable of the reactant. The enzyme which will be used is different concentrations of potato and the reactant used will be Hydrogen Peroxide. Hydrogen Peroxide which will be the buffer solution is a PH of 7. 2. My hypothesis for the experiment is that as the concentration of the enzyme is increased the rate of reaction will be increased, producing oxygen at a faster rate. The results in my opinion will show positive correlation.
The amount of buffer solution (hydrogen peroxide) will be kept the same throughout the experiment in the interest of reliability and the amount of enzyme (potato) will be decreased as the experiment is carried out and a measurement will be taken as to how fast the enzyme is produced. Variables The independent variable for this investigation will be the amount of enzyme which will be reacting with the Hydrogen Peroxide solution. I will be using potato as the enzyme in the reaction and the amount of potato will begin at 5ml and decrease by 1ml increments until it reaches 1ml which will be the final measurement.
The dependent variable in this investigation will be the rate of the reaction between the enzyme and the buffer solution. According to my hypothesis the rate of reaction will decrease as the amount of enzyme is decreased and the reaction will take longer to produce a particular amount of oxygen as the amount of enzyme is decreased. The controlled variables in my experiment are the amount of hydrogen peroxide which acts as the buffer solution, this is necessary in order to ensure accurate results.
The boiling tube in which the reaction takes place will also be kept the same and will be cleaned out with water after each reaction. This is necessary to avoid contamination of the rest of the reactions by surplus potato or hydrogen peroxide. The delivery tube will also be cleaned and kept the same, for the same reasons as the boiling tube. The water which the syringe is collecting the oxygen, will be changed after each reaction and the amount of water will be kept the same, this would not significantly affect the experiment but is controlled in the interest of validity.
The amount of hydrogen peroxide must be kept the same as if the amount were to be changed then the entirety of the experiment would be affected and it would completely compromise the investigation. The boiling tube in which the reaction takes place must be controlled as if it was not then the following experiments could be contaminated by surplus enzyme or hydrogen peroxide. The delivery tube which is used must also be kept the same and cleaned in order to prevent the same contamination as the boiling tube.
The water being changed and the amount of water being kept the same would not significantly affect the results of the reaction but is kept the same in the interest of validity. Method 1. Set up the apparatus: Place the boiling tube in a test tube rack and place the delivery tube’s bung in the top of the tube. Place the other end of the delivery tube in a beaker filled with water, and then place the syringe barrel which is used for collecting the oxygen with the screw clip on the end, over the end of the delivery tube, and this is how the oxygen will be collected. 2.
Blend a quantity of potato and place 5cm3 of it in the boiling tube along with 5cm3 of buffer solution. 3. When the hydrogen peroxide solution is added to the potato juice, immediately place the bung and delivery tube firmly into the boiling tube. Place the other end of the delivery tube under the collecting tube. 4. Start a stop clock as soon as the first bubble of oxygen enters the collecting tube from the delivery tube. Collect any gas produced in a three-minute period. Shake the boiling tube gently throughout the reaction period to keep the contents well mixed.
If no gas bubble is produced within three minutes of adding the hydrogen peroxide record a zero value for the test. 5. Measure the volume of oxygen produced in a three minute period; raise the collecting tube so that the water level in the tube is level with the surrounding water level in the beaker. 6. Wash out the boiling tube thoroughly. 7. Repeat the steps 1 to 6 each time decreasing the amount of potato by 1ml each time, ensuring that no other conditions are unchanged, as this would lead to unreliability. Open the screw clip to refill the collecting
tube and then tighten again. Results This is a table of results that I collected throughout the course of the experiment. Any anomalies are shown in bold. | | Rate of reaction. (time taken for gas to fill syringe) (seconds). | | | | Amount of Hydrogen Peroxide (ml)| Amount of Potato (ml)| Test 1. | Test 2. | Test 3. | Average result (excluding anomalies). | 5ml| 5ml| 9. 00 | 6. 01| 7. 00| 6. 505| 5ml| 4ml| 7. 01| 7. 06| 8. 00| 7. 35| 5ml| 3ml| 17. 01| 17. 00| 19. 00| 17. 67| 5ml| 2ml| 49. 05| 50. 01| 45. 03| 48. 03| 5ml| 1ml| 154. 03| 135. 06| 151.7| 146. 72|
Validity I have a great degree of confidence in the reliability of my results. This is because my experiment was completed to a high degree of accuracy and care and therefore there was only one anomaly. Having the 10% increments in the concentration of ethanol has allowed me to easily see patterns and trends in the data, and on the graph I have drawn it is possible to see this correlation, that as the volume of enzyme was decreased, the rate of reaction decreased and it took longer to collect oxygen in the syringe barrel. Reliability.
Excluding the anomaly which has occurred on the first attempt of the experiment, my method has given me completely consistent results and it shows that the rate of reaction has decreased due to the decreasing amount of enzyme. My repeats give very sufficient replication of my results with only a small error range. The anomaly may have been caused by the delivery tube popping out of the syringe barrel and the gas escaping. Systematic Error There may have been a form of systematic error in the aspect of the syringe barrel which was used to collect and measure the oxygen produced by the reaction.
The syringe being filled with the gas may not have been accurately filled with water before the reaction took place. This would have been the same for each of the experiments which would have made it a systematic error. The syringe itself may not have been the correct piece of equipment with which to collect the gas as it does not function to a particularly good accuracy. Random Error There may have been a number of random errors present in the investigation.
The delivery tube may have escaped from the syringe barrel meaning that some of the oxygen was lost in the beaker before it was reinserted. This would have affected the reliability of the results as the reaction time would have been recorded to have decreased which would not be correct. The time delay between starting the stopwatch and adding the hydrogen peroxide may also have affected the results, as the equipment could not be used to such a degree of precision which would have neutralised the time delay and this could have affected the reliability.
My results do not seem to have been affected by these, and if they were it was not significant so it therefore does not affect the reliability of my results. Conclusion My results show a reliable example of positive correlation. That as the volume of enzyme is decreased, and then the rate of reaction also decreases. By using 1ml increments between my measurements, it has allowed me to easily identify this, and by looking at my graph it is evident that this correlation is the case. The potato enzyme and the hydrogen peroxide are shown to have been proved that they produce oxygen when reacted.
Evaluation Overall throughout my experiment there was one anomaly which somewhat took away from the validity of my first set of results but this outlier was created on the first attempt at the experiment and therefore was likely due to the poor execution of the reaction as it was my first attempt at the experiment. The method allowed the experiment to be conducted to a high degree of accuracy, as the controlled variables such as the cleaning thoroughly of the boiling tube decreased the likelihood of systematic error.
The method however did not provide a way for the delivery tube to be firmly seated beneath the syringe barrel without the risk of it escaping and losing oxygen in the beaker of water, and this may have accounted for the anomaly in my first set of results. The problem of the time delay between starting the stopwatch and actually adding the hydrogen peroxide to the boiling tube was another problem with the method, which could affect the validity. The investigation could be extended by having more repeats of the experiment, than previously as this would have meant that the anomaly in the first set of results could have been completely discredited, and this may have shown the cause of the anomaly.