Science Buddies: "Ask an Expert"

Hello, I am doing a project related to electrolytes.
With reference to https://www.sciencebuddies.org/science- ... nk#summary,
I am doing a comparison of electrolytes of different juices.
The project procedure says to measure conductance, but considering the voltage will be the same throughout (9v battery), can we determine electrolytes with just the current from multimeter?

Thanks

Hi itshsu,

In the Electrolyte Challenge, you use a conductance sensor to measure the current in orange juice and sports drink samples. The current is directly proportional to the conductance (as shown by equation 1 in the project background) so you could just report the current. But the conductance is a property of an electrolyte solution and its more relevant to report the conductance values.

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

A. Norman

norman40 wrote:Hi itshsu,

In the Electrolyte Challenge, you use a conductance sensor to measure the current in orange juice and sports drink samples. The current is directly proportional to the conductance (as shown by equation 1 in the project background) so you could just report the current. But the conductance is a property of an electrolyte solution and its more relevant to report the conductance values.

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

A. Norman

Thanks for the help! I have more questions
I seem to only get results when I turn the multimeter to the green 200 and green 20, whereas when I try with 200u and 200m, the reading remains as 0.
In what units do I measure these results in?
And why don't the 200u and 200m settings work, the circuit is properly connected. thanks!

Hi itshsu,

Science Buddies has an excellent tutorial on using multimeters that may be helpful to you:

https://www.sciencebuddies.org/science- ... eroverview

You want to measure current using the 200 u range (microamp) for distilled water and the 200 m (milliamp) for the orange juice and sports drink.

If you've set up the circuit as shown in the project procedure and the multimeter displays 0 when set to the 200 u range there's no current in the circuit. First, check to be sure that all of the wires are properly connected in the circuit. Make sure the conductance sensor is immersed in water as shown in the project procedure. Also, make sure you have a good 9 volt battery installed in the circuit.

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

A. Norman

Hi. I am i need of desperate help for my science project.

Does pH level of a certain fruit affect electrolytes inside?
For example, if a lemon is more acidic compared to orange, would it mean that there would be more electrolytes in a lemon?
Is there anything else that affects electrolyte value of a fruit?

moderator note: Please keep your posts together in the same thread so the expert who has been helping you can see that you have posted a follow-up. Thank you and best of luck with your project.

Hello itshsu,

An electrolyte is something that dissociates into ions when dissolved in a solution. An acid is an example of an electrolyte because hydrogen ions dissociate from acids in solution.

The pH is defined as the negative logarithm of the hydrogen ion concentration. So the pH of a solution is lower when the concentration of hydrogen ions is higher. And a higher concentration of ions equates to a higher concentration of electrolytes.

In your example, lemon juice has a lower pH than orange juice. That means that the hydrogen ion concentration is higher in lemon juice. Since hydrogen ions are electrolytes, the lemon juice has a higher electrolyte concentration.

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

A. Norman