How brewing time affects tea strength

[deleted-407904]

I did this experiment where I am measuring how brewing time affects strength of tea, using a device that measures light absorption. I am using a photoresistor to measure resistance of tea brewed for different times. I was expecting that the more time I am brewing the tea, the more will be the resistance (because the tea will get darker). I see that for some time intervals when the resistance is increasing as I increase the brew time from 10s to 30s, 60s, 90s, 180s and 240s. But after 300s, the resistance is actually lower than 240s. That is confusing. Why would the resistance be lower after a set amount of time? Any thoughts? Has anyone else done this experiment and found similar results?

[deleted-2131]

Hi rohankohli0820,

I agree that your result is counterintuitive. Kudos to you for trying to figure out why your results turned out the way that they did!

You're doing this project, correct?
https://www.sciencebuddies.org/science- ... p058.shtml

One possibility is that some of the compounds that initially dissolved into the water are breaking down when the tea has for 300 seconds. If the breakdown products don't absorb as much light, then perhaps the resistance would drop because more light would reach the bottom of the cup. I'm not familiar enough with the detailed chemistry of tea making to know how plausible this explanation might be.

Alternatively, something about your measurement setup may have changed in some way. I'n inclined to think that this is the more likely scenario. Perhaps the light in the room was slightly brighter when you measured the 300 second cup? Or the aluminum foil shifted slightly, which let in light from the side?

If your science fair project is due soon, then one way of dealing with this would be to say in your results/conclusion section that the 300 second brew result seemed unusual based on your other results. If you have more time between now and when your project is due, you could also re-run the experiment and see if you get the same results.

It's quite common for professional scientists to re-run an experiment if the result is unexpected. If the result is still unexpected, then the scientist would dig deeper to find out why. But, if the result of the re-run experiment is in line with what the scientist expected, then the scientist would conclude that the first experiment was somehow flawed.

Post back as you have other questions.