At the beginning of every unit on electricity, it helps to discuss conductivity. This is a great lab for letting students investigate the differences between conductors and insulators. If you are able to extract a thick pencil lead, students can even observe a resistor (the graphite of the lead conducts electricity, with increasing resistance as the distance between the test leads increases).
I have included both PDF and Word files. I have made a suggested list of items to try, but you may modify this as you see fit. The dry sponge does not conduct, and the wet sponge does (but depending on your bulbs, the wet sponge may not conduct enough current to light the bulb. You can still measure the current with a multi-meter).
I have included an answer key for the fill-in the blank questions, but I will leave it to you to decide how much detail you would like on the long answer questions.
I like to precede this lab with a short introduction to the periodic table of elements and the basic structure of atoms - not a chemistry unit, but enough to let the students understand that electricity is a physical thing.