6. "Diamonds Are Just Compressed Coal"
One of those facts that seems mindblowing to a class of 11-year-olds is that coal and diamonds are both made from the same thing, carbon. This is undoubtedly a great way of demonstrating how elements can make up all kinds of different materials, but it's not quite as simple as coal + pressure = diamonds forever. Whilst it's a nice thought that you can take an ugly lump of coal and pressure it into being pretty (societal pressures, amiright?), the carbon in diamonds almost certainly didn't come from coal. Coal and diamonds are almost never found in the same place. Coal is made near the Earth's surface from ancient plant matter, whereas diamonds are forged deep in the Earth's mantle and are carried to the surface by volcanic activity. Although, thanks to the wonders of modern science, you can create diamonds in the lab. If you can afford the initial outlay for the specialised equipment, then perhaps buying up bags of coal and producing bags of diamonds is a good business model.