One super awesome idea: Check!
One lemon, some copper wire, a copper nail, a zinc-coated nail, a 1.5 V tiny light bulb: Check!
One battery made from a lemon used to power above-mentioned light bulb: Ready for lift-off!
You see? See the LCD display ALL LIT UP?! See it working?! (Battery placed nearby so you can tell it's not a rigged shot). It really, truly worked. I was beside myself with glee. "Wooooow coooool" I said, congratulating myself heartily.
There was an eerie silence from the children. My point earlier: most science resources are aimed at older kids. My children don't know how a regular battery works let alone one made from a lemon. They see things lit up from batteries all the time and lighting up the pedometer didn't impress them one bit. As well, all the problem-solving was done by me- I wired up the extra lemons, then knew enough to know we'd need something with a lower voltage drain. They had no investment in this experiment at all, and conseqently no interest. Back to the drawing board then.
Something simpler. Something visual. Something that they can do themselves with tools they use all the time: A simple circuit with a battery and a tiny light. The kids connect the wires to the battery all by themselves using cellotape. (Approximate cost: $3.00 for the battery and $0.86 for the little light from Dick Smith Electronics). They soon worked out that both wires must be attached (it must be a complete circuit) and that the wires must be touching the metal itself. That's pretty good problem solving and they did that all by themselves.
And this is the reaction I was looking for:
The light they made all by themselves was carried around all day, taped to a hat to make a head light, pushed into tiny spaces to see what they could see in there, and was frequently connected and disconnected. That's what I call an experimental success.
(P.S. Even though my very little children weren't interested in the lemon battery, it would be great for older kids. I have loads of copper wire, copper nails, and zinc coated nails leftover and I will gift them to NZ readers until I run out. Email me at firstname.lastname@example.org if you would like me to post some to you, along with the wiring layout for making a lemon battery. NZ readers only, sorry, postage costs get a wee bit prohibitive to anywhere else.)