◆ We begin with a brief introduction to the study of chemistry and describe its role in our modern society. (1.1 and 1.2) ◆ Next, we learn the basic SI units and use the SIderived units for quantities like volume and density. (1.3) ◆ We become familiar with the significant figures. In calculations or measurements, every quantity must show the proper number of significant figures, which are the meaningful digits.◆ We study the four major types of concentration units—percent by mass, mole fraction, molarity, and their interconversions.