CHEM 101 Lecture Notes - Lecture 2: Thermal Energy, Significant Figures, Metric System
Document Summary
The units of measurement: units are quantities used to specify measurements, which are critical in chemistry. The two most common unit systems are as follows: Metric system, used in most of the world. English system, used in the united states. Scientists use the international system of units (si), which is based on the metric system. The abbreviation si comes from the french phrase syst me international d"unit s. Reliability of measurements: precision and accuracy: accuracy refers to how close the measured value is to the actual value, precision refers to how close a series of measurements are to one another or how reproducible they are. Precision and accuracy: measurements are said to be, precise if they are consistent with one another; accurate only if they are close to the actual value. Scientific measurements are reported so that every digit is certain with the exception of the last digit, which is estimated. Consider the following reported value of 5. 213:
