I'm doing an experiment for Year 11 Biology to model how increasing the surface area of a potato affects the height of bubbles produced during a chemical reaction. It's supposed to show the interaction between the enzyme catalase and hydrogen peroxide. My current method involves cutting a potato into $\pu{24 cm2}$, $\pu{32 cm2}$, $\pu{40 cm2}$ and $\pu{48 cm2}$ pieces and measuring the height of bubbles produced after two minutes. How can I add a control group to this experiment, or am I just not thinking right and I already have one? I'd appreciate any responses:)
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1$\begingroup$ What exactly do you mean by the height of bubbles and why is it a good quantitative parameter? $\endgroup$– PoutnikCommented May 25 at 9:01
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$\begingroup$ @Poutnik Sorry for the confusion! That parameter is mandated by the teachers, I'm pretty sure the amount of bubbles are supposed to reflect how much oxygen (product) is produced in the decomposition reaction of catalase and hydrogen peroxide. $\endgroup$– KatherineCommented May 25 at 10:02
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$\begingroup$ I don't think there can be a control group. For instance, if you were boiling potatoes and then working with them to see how the temperature of the cooking water affects the presence of the enzyme catalase (interaction between the enzyme catalase and hydrogen peroxide), you could have kept an uncooked potato as a control. In the case of surface area, I don't really see a control(unless you have an invisible potato xD) $\endgroup$– RonithCommented May 25 at 10:18
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1$\begingroup$ @Ronith Thank you so much!! That's what I was thinking as well:) I really appreciate the response! $\endgroup$– KatherineCommented May 25 at 10:54
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1$\begingroup$ Negative control: leave out the potato. Positive control: add $\ce{MnO2}$ instead. The purpose is to show that hydrogen peroxide is stable in the absence of the catalyst, and that the bubbles reflect the reaction of hydrogen peroxide and not something else (I don't know, the potato doing photosynthesis or some other red herring). $\endgroup$– Karsten ♦Commented May 25 at 11:58
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