I did an experiment where I tested the conductivity of different solutions and some substances. We connected a 9 bolt battery, some aluminum foil sticks, and a multimeter that reads the voltage. It connects like liquid --> aluminum --> multimeter --> battery --> aluminum --> liquid.
My understanding is that if a liquid contains more ions, it conducts electricity better. Here's my question. We tested the battery just by itself and it read about 9 volts. When we tested with baking soda, it reads about 9.2 volts. How can it be higher than the energy source? Does baking soda produce its own electricity? Also, when we tested deionized water, it came out to be about 8.5. It seems close to 9, but it was one of the lowest of the tested solutions. Why is it like this? If it's deionzed, shouldn't it be nearly zero? since it doesn't conduct electricity at all? (although there can be impurities so it can have some, but I think 8.5 is still too much). I don't really understand. Can someone explain why the results came out like this?