Ask A Scientist Chemistry Archive

name         Elizabeth E.
status       other
age          40s

Question -   On the lemon battery experiment, does the pH of the electrolyte (lemon vs. lime vs. potato vs. whatever) affect the voltage create by a pair of zinc and copper electrodes?  If so, how? And could you explain why?  Or, does it affect the conductivity, and thus the current of the charge?
Any insight will be much appreciated.  I am trying to do this experiment at home for my children who say they hate science and I am trying to change their minds!
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Elizabeth,

The most important factor influencing the voltage is the electrochemical differences between the 
metals. All that's necessary is that the lemon/lime/potato be sufficiently conductive so that 
electron flow is enabled. Different metal pairs will produce different voltages.

Try this experiment; the kids will love it. By the way, the demonstration is safe and harmless:

Polish the metal strips so that maximum conductivity is possible and then hook a sensitive 
voltmeter between the metal strips. Have the child hold one metal strip in each hand so as to 
make a complete circuit between the plates and the voltmeter. Different people have different 
bodily conductivity. Those with the greatest conductivity will en
able the greatest voltage reading -- up to the maximum allowed by the metal pairs selected.
For further excitement and debate, try this:
Instead of having the child hold one metal strip in each hand, have two children each hold one 
strip in one hand, and then have them join their free hands. Different pairs of children will 
produce different results. You can then make whatever you like of these differences -- a sort of 
"love" meter, if you will.

Regards,
ProfHoff 646
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