Measurement in Chemistry: - Fundamental and Derived Units

Measurement in Chemistry: - Fundamental and Derived Units:-

Chemistry is an experimental science. An experiment always involves observation of a phenomenon under certain set of conditions. The quantitative scientific observation generally requires the measurement of one or more physical quantities such as mass, length, density, volume, pressure, temperature etc.

A physical quantity is expressed in terms of a number and a unit. Without mentioning the unit (inch, centimeter, meter etc) is associated with the number. The units of physical quantities depens on three basic units, i.e., units of mass, length and time. Since these are independent units and cannot be derived from any other units, they are called fundamentals units. It was soon realized that the three fundamental units cannot describe all the physical quantities such as temperature, intensity of luminosity, electric current and the amount of the substance. Thus, seven units of measurement, namely mass, length, time, temperature, electron current, luminous intensity and amount of substances are taken as basic units. All other units can be derived from them and are, therefore, called derived units. The units of area, volume, force work, density, velocity, energy, etc., are all derived units.