(cm3).
Controlled Variables.
- name.
- how to control it.
- the effect on the experiment.
Volume of Hydrogen Peroxide.
I specifically measured 5 cm3 of hydrogen peroxide using a measuring cylinder provided to us.
If the volume of hydrogen peroxide is inaccurate, the rate of reaction varies depending on whether the volume is too little or too large. Should we measure the volume of hydrogen peroxide inaccurately and measure a bigger volume of hydrogen peroxide then we would expect to see the rate of reaction increase. The same goes if we measure too little, in which the reaction rate would be too little. .
Concentration of Hydrogen Peroxide.
We have all been allocated a 20% concentration solution of hydrogen peroxide so this will remain constant as it is all from one batch. If there is a slight difference in the concentration of hydrogen peroxide, the number of substrates to be catalysed by the enzyme varies depending on whether the concentration is higher or lower than 20%. The rate of reaction corresponds to the direction of the concentration gradient (e.g. lower than 20% = slow rate of reactopm).
Reaction Time.
We will give the potential reaction 30 seconds to occur by using a stopwatch to record the time.
We must control this in order to keep our results valid and accurate. All tests must be timed to perfection in order to get a specific amount of gas released into the gas syringe for each pH solution.
Temperature of the Reaction.
The temperature of the surroundings must remain constant throughout this experiment. .
As we know from our fundamental knowledge on enzymes we derived from the IB Course; temperature affects the activity of an enzyme. Any temperature apart from the optimum is unsuitable to work in as it can affect the rate of reaction and we are not looking at how temperature affects the activity but we are looking at how pH affects the activity.
Volume of Catalase in the Enzyme Solution.
We measured 6.