Science Buddies: "Ask an Expert"

Hi,
My friend and I are doing the "How Blue is your Sports Drink?" Science fair project. We are having trouble understanding the analyzing your results part of the procedure. What does it mean by resistance readings and calibration curve?
The graphing is a little bit shaky with us, it says "Graph the average resistance of your three readings on the y-axis versus the concentration of the standard solutions in µM on the x-axis." Can you explain this further?
And last, did the sports drinks have to be diluted? We just measured them in the same level (2000).
Thank you so much

Hi Phoebe820,

I’m assuming that you’re working on the project described here:

https://www.sciencebuddies.org/science- ... ml#summary

In this project you measure the amount of light passing through the various solutions with a photoresistor. So “resistance readings” in the procedure section refers to your measurements of resistance for the blue dye and the sports drink solutions.

The resistance of the photoresister changes with the concentration of blue dye in the solution. You need to make a “calibration curve” to use the relationship between concentration and resistance to find out the concentration of blue dye in sports drink samples. And Part 2 of the procedure outlines the steps for collecting the data you need to make the calibration curve.

After collecting the data for the calibration curve, you need to make a graph of the data. You should have a table of data with the resistance values you measured for each blue dye concentration. Plot the concentration data on the x-axis and the corresponding resistance data on the y-axis. If you made 3 resistance measurements for each concentration you can plot all of them on the graph.

Some information on making x-y graphs that you may find useful can be found at the following links:

https://www.sciencebuddies.org/science- ... ml#keyinfo

http://serc.carleton.edu/mathyouneed/gr ... index.html

https://www.khanacademy.org/math/probab ... atter-plot

https://www.mathsisfun.com/data/scatter-xy-plots.html

You might need to dilute one or more of your sports drink samples. You should dilute if the resistance reading for the undiluted drink is greater than the highest resistance in your calibration data. In other words, you want all of your sports drink resistance readings to be within the range of your calibration resistance data.

I hope this helps. Please post again if you have more questions.

A. Norman