However, it is quite useful if we apply it to other substances, especially elements. Scientists have then defined the molar mass of a substance as the mass of 6.02214076 x 10 23 units of that substance. Figure 2: Carbon-12, with 6 protons and 6 neutrons, is the isotope that used to define one mole. Regardless of whether the substance is 12C, electrons, or gray squirrels, one mole represents the same number of each of these things. Experiments counting the number of 12C atoms in a 12-gram sample have determined that this number is 6.02214076 x 10 23.

The International Committee for Weights and Measures-a group that defines the metric system’s units of measurement (for more information, see our module on The Metric System)-defines one mole as the number of atoms in exactly 12 grams of carbon-12 ( 12C, Figure 2). 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. 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, molecules, and electrons-although the mole’s usefulness goes beyond being a helpful scientific term. Obviously, the mole is not a term we need for most things in daily life. And one mole of gray squirrels weighs 301,000,000,000,000,000,000,000,000 grams-more than four times the mass of the moon! Figure 1: An Eastern Gray Squirrel. One dozen gray squirrels weigh about 6,000 grams, or a little more than a medium-sized bowling ball. One gray squirrel weighs roughly 500 grams, or as much as a hardback book. This is a huge number! To help you and any wildlife biologists reading this module get a sense of just how many things are in one mole, we can use an analogy with another small, gray rodent: the gray squirrel (Figure 1). In this case, one mole represents the enormous (and slightly strange) number, 6.02 x 10 23. The term ‘mole’ represents a number, in the same way the word ‘dozen’ represents 12 of something. But when chemists talk about moles, they’re usually referring to a scientific term. When wildlife biologists talk about moles, they’re usually referring to the tiny, gray rodents that dig underground to find delicious earthworms. This is an updated version of The Mole module.

Understanding Scientific Journals and Articles.Using Graphs and Visual Data in Science.Scientists and the Scientific Community.Scientific Notation and Order of Magnitude.The Case of the Ivory-billed Woodpecker.Santiago Ramón y Cajal and Camillo Golgi.Factors that Control Earth's Temperature.Plates, Plate Boundaries, and Driving Forces.Solutions, Solubility, and Colligative Properties.Y-Chromsome and Mitochondrial DNA Haplotypes.Absorption, Distribution, and Storage of Chemicals.

Atomic mass unit