measurementsystems

Measurement Systems

• The United States uses the English/Imperial System of units (pounds, ounces, cups, inches etc)
• The rest of the world uses Metric or System International (SI) system
• In Chemistry (and nearly all other science classes) we will be using the metric & SI system.

Units are the letters that come after a number, like cm (stands for centimeters). A unit describes the type of measurement. The base units, and their notation (in parenthesis) you should know are:

SI Units to Know

The ampere (A) - unit of measurement of electric current

The kilogram (kg)* - unit of measurement of mass.

The meter (m) - unit of measurement of length

The Liter (L) - unit of measurement of volume

The second (s) - unit of measurement of time

The kelvin (K) - unit of measurement of thermodynamic temperature

The mole (mol) - unit of measurement of amount of substance. 6.02 X 10²³ of anything!

The candela (cd) - unit of measurement of luminous (light) intensity

* The base unit for conversion purposes is the gram.

-Units above in bold are the main units we will use in Chemistry. You should ABSOLUTELY know these.

-A notable Exception is Celsius. We often still use Celsius (which is a metric unit) in Chemistry.

Check out the video below: "The Roundest Object in the World" about why the kilogram (and not the gram) is the standard unit of the SI system:

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