MEASUREMENTS AND CALCULATIONS
The student of chemistry must be able to make good observations. Observations
are either qualitative or quantitative. Qualitative observations involve
descriptions of the nature of the substances under investigation. Quantitative
observations involve making measurements to describe the substances under
observation. The chemistry student must also be able to use correct measurement
terms and the required mathematical skills to solve the problems. The following
sections review these topics.
Metric System
It is important that scientists around the world use the same units when
communicating information. For this reason, scientists use the modernized metric
system, designated in 1960 by the General Conference on Weights and Measures
as the International System of Units. This is commonly known as SI, an
abbreviation for the French name Le Système International d’Unités. It is now the
most common system of measurement in the world. There are minor differences
between the SI and metric systems. For the most part, the quantities are
interchangeable.
TIP
Only metric units are used on the SAT test.The reason SI is so widely accepted is twofold. First, it uses the decimal
system as its base. Second, many units for various quantities are defined in terms
of units for simpler quantities.