When a mole of a substance is considered, how is the atomic mass usually expressed?

The atomic mass of a substance is usually expressed in grams when considering a mole of that substance because of the relationship defined by the mole concept. The mole is a unit that relates the amount of substance to the mass of that substance. Specifically, one mole of a substance has a mass in grams equal to its molecular or atomic mass expressed in atomic mass units (amu). This is known as the molar mass.

For example, the atomic mass of carbon is about 12 amu, meaning one mole of carbon weighs approximately 12 grams. Therefore, when discussing a mole of a substance, it is common practice to express the atomic mass in grams, aligning with the definition that integrates the macroscopic scale with the microscopic properties of matter. This approach allows chemists to easily convert between the amount of substance in moles and its corresponding mass in grams for practical calculations in chemical reactions and analyses.