"Oh, and one more warning...never carry 9 volt batteries in your change pocket. :-)
I'm not even going to ask how you learned that bit of information.
I'll never forget my very first experience with 9v batteries. my dad had given me a little 2 transistor radio when it came time to replace the battery I somehow managed to pinch the tiny wires of the contact clip between the radio and the battery A few minutes later the radio was getting warm in my pocket by the time I got the battery out it was hot enough to burn my fingers after getting the wires separated and taped the radio was fine but I didn't have any finger prints on my thumb and fore finger for a while. Lesson learned 7 year olds don't always know as much as they think they do.