Science Buddies: "Ask an Expert"

Hi. I am a ninth grader doing the Electrolyte Challenge science fair project. I completed my project in December, and I wound up changing my procedure a little bit. I used a M-2625 Autoranging Digital Multimeter to record the current and the voltage of my substances (Orange Juice, water, Gatorade, Choc Milk). However, to do this I put the probes directly in the substances to measure the current and voltage. I then plugged the results into the equation (Current/Voltage= Conductance). I was wondering if the way I completed the experiment is still accurate, because if otherwise I do not enough time to redo the experiment .


The results of my experiment are here: https://docs.google.com/a/ndapa.org/doc ... sp=sharing

Please help me with this, it is extremely important!

Hello jlanzalotto,

If I understand your procedure correctly, you put the probes from the multimeter directly into the various liquids. This suggests that you did not use the 9V battery. (Other experts please correct me if I'm wrong) It seems that the objective is to measure how the current from the battery is conducted through the liquid. So without the 9V battery, you wouldn't have any current to be conducted. If you didn't use the 9V battery, then it would seem that, sadly, your results aren't measuring what you want to measure.

If you look at the section "Make It Your Own", you'll see that the water should have a conductance of 1.0.

It would help if you could clarify if you did use a 9V battery, and how you connected it to the probes.

I did not use a battery

Hello jlanzalotto,

Thank you for that clarification. I suggest that the measurements will not be meaningful unless you use the 9V battery with the conductance sensor and alligator clips as illustrated here:

https://www.sciencebuddies.org/science- ... #procedure

I realize that you might feel frustrated at having to remeasure the conductance. Doing science often means having to repeat experiments!

Please let us know your new results!

Thanks for helping. I will redo my experiment and share my results.

Hooray jlanzalotto!

Your report will be even better, since you can show the results obtained using the 9V battery and the results obtained without the battery.
Best wishes!

Thanks! I have successfully completed my experiment and will compete this weekend!

Fantastic! And good luck!