Science Buddies: "Ask an Expert"

I am having trouble with my science fair project. I did the electrolyte challenge: sports drink vs. Orange juice. According to my research, I should be getting the Gatorade with the highest conductance, therefore the one with the most electrolytes but my project keeps on resulting with the orange juice. What is happening? Can you give me some advice?

We keep on getting orange juice. The results from our test showed the orange juice with the most electrolytes. Do that make sense or is it wrong? If it is wrong, what caused it to happen? Why do we keep on getting that? (we've done the test 5 times already and it's due this Friday!)

tom and dad - Actually, orange juice has a pretty high electrolyte value. What are you comparing it with? If you did readings on tap water and distilled water you might have noticed much lower conductivity readings. Some sports drinks like Gatorade and others usually measure higher conductivity than orange juice. At this point it can't be said that your measurements are wrong, but you should review them in comparison with your other readings and expectations. By the way, what current measurements were you observing?

Rick Marz

Rick, O.J in comparison to the Gatorade was higher. The current measurements we were observing were: distilled water average: 49.36 micro amps, tap water average: 5.23 milliamps, sports drink average: 38.6 milli amps, and orange juice average: 51.56 milli amps. In the end, the sports drink to the orange juice conductivity was 0.0042888 to 0.0057288 meaning the orange juice had the most electrolytes. Does that make sense? Or did we do something wrong to end with these results?
Thanks,
Tom

tom and dad - In general, your readings are very consistent with the way they should turn out. It appears that your setup is probably correct. I have done this experiment several times and agree that your values for distilled and tap water are pretty consistent. The reading for orange juice is similar with what I have measured, the outlier seems to be the sports drink. My experience is that OJ tends to measure 30-50 milliamps. I have seen the value for Gatorade be about twice the OJ value at around 80 milliamps. I suggest you check that your battery is good, and try another sample of Gatorade. While it's possible that you have a unique batch of OJ that is uniquely 'ionic', I think the problem is the sports drink. Perhaps try another brand or lot.

Rick Marz