To help you and any bakers or hungry biologists reading this get a sense of just how many things are in one mole, we can use an analogy with something that is often found in dozens (Figure 1). One yeast-raised doughnut weighs approximately 40 grams. One dozen yeast-raised doughnuts weigh about 500 grams. One mole of yeast-raised doughnuts weighs about 301,000,000,000,000,000,000,000,000 grams—more than four times the mass of the moon. Imagine the whole moon made of doughnuts, yummy...

Figure 1: A dozen yeast-raised donuts

Obviously, the mole is not a term we need for most things in daily life. Instead of being used for things we encounter in daily life, the mole is used by scientists when talking about enormous numbers of particles like atoms or molecules. Atoms and molecules are very tiny things. A drop of water the size of the period at the end of this sentence would contain 10 trillion water molecules. Instead of talking about trillions and quadrillions of molecules (and more), it's much simpler to use the mole. However, the mole does more than represent a big number: it provides a key link for converting between the number (amount) of a substance, and its mass.