Numbers and Chemistry Numbers play a major role in chemistry. Many topics are quantitative (have a numerical value). Concepts of numbers in science Units of measurement Quantities that are measured and calculated Uncertainty in measurement Significant figures Dimensional analysis Units of Measurements?SI Units Syst?me International d?Unit?s (?The International System of Units?) A different base unit is used for each quantity. 3 Units of Measurement?Metric System The base units used in the metric system Mass: gram (g) Length: meter (m) Time: second (s or sec) Temperature: degrees Celsius (oC) or Kelvins (K) Amount of a substance: mole (mol) Volume: cubic centimeter (cc or cm3) or liter (l) Units of Measurement?Metric System Prefixes