Reader Maddy nominated a classmate as today's example of what not to say when trying to impress science buffs (or for that matter, anyone else):

From the mewling spastic who sits in front of me in chemistry... "Sir! What's the chemical formula for wood?"

Now, in this idiot's defense, there is one type of wood that has a chemical formula -- the petrified variety, which of course isn't really wood at all but a fossil in which all of the wood's organic matter has been replaced by minerals. Usually, the mineral that seeps into the wood is a silicate such as quartz. So, to answer this unfortunate student's question, the chemical formula for (petrified) wood is usually SiO2.