Science Buddies: "Ask an Expert"

Hi I just finished my 1st trial and the readings I got were water - 0.0mA, juice - 0.2mA and gatorade - 0.1mA. Am I on track??? I am guessing that the juice is reading higher because of the higher amount of sugar in it???

Guidance please!

mrscience - The readings you are getting are based on the following factors:

1) Pure water is not a conductor as it has no free ions to conduct electricity. It actually could be considered a pretty good insulator.
2) Gatorade or other similar sports drinks do replace the bodies electrolytes and have certain salts in their composition which are very ionic and therefore conductive to electric current.
3) The juice you tested as having higher conductivity than the sports drink probably has even more ionic salts than the sports drink, giving you more conductivity, and a higher current reading, but it is not a factor of the sugar content.
4) Sugar, or more precisely, sucrose, is not an ionic material, so the sugar content in the juice is not a contributor to the conductivity you have observed.

Hope this helps.

Rick Marz

If you really want to understand more of the technical aspects of electro chemistry involved in this experiment, you should do some more reading on pH, ions, and ion concentration, acids, bases, and salts.

If the juice you measured was orange juice or grapefruit juice, both of which are acidic, the pH would be much lower than gatorade. The pH is an indication of the balance between free +ions and -ions. The lower the pH, the stronger the acid and the more free +ions there are which means the more conductive the liquid.

Gatorade is designed to be a netral pH (balanced + and - ions) which means there the ionic forces between + and - ions must be overcome in order to conduct electricity which means some of the voltage in your conductivity measurement circuit will be used to overcome the ionic forces so the conductivity will be slightly less than if the pH were lower (more + ions) or higher (more - ions) for the same number of ions per volume of solution.

In other words, there are at least two factors to conductivity: 1) ion concentration, and 2) pH.

The previous responder was correct to point out that sugars are non-polar and do not contribute to the ion concentration.

possibly could you use a smaller scale to measure on? that way you would see a difference more clearly.