In the preceding chapters, you should have gained an appreciation of the scale of chemistry, with regard to the physical size and mass of individual atoms and compounds. Because a typical samples of a substance (such as a copper penny) contains so many atoms, chemistry have defined a unit by which we can easily county these large numbers; this units is called a mole. However, we will see that a mole is more than a just a large number; a mole is also directly related to the atomic weight of atoms and compounds and the mole concept will give us the tools to consider chemical reactions in a quantitative manner. This chapter serves as an introduction to the concepts and we will continues to build upon this foundation when we consider stoichiometry in the following chapters.
Thumbnail: A photograph of Scalopus aquaticus. The eastern American mole (Scalopus aquaticus linnacus) showing the large forelimbs used to excavate tunnels. (CC BY-SA 3.0; Kenneth Catania, Vanderbilt University).