There are many molecules underground that turn into gases/vapors when they are released from their underground reservoir. Many of them are molecules made of one, two, three, or four carbon atoms, and enough hydrogen atoms to “saturate” the carbon. In other words, the carbon is completely surrounded by hydrogen atoms unless it is connected to another carbon atom. This link allows you to see four common molecules and learn their names, formulae, and structure. As you complete this matching exercise, note that the list goes from lightweight molecules at the top to heavier molecules at the bottom. After you match the names, try building the molecules using our model kits.