Every substance has unique or characteristic properties. 

These properties can be classified into two categories – 

Physical properties and chemical properties. 

Physical properties are those properties which can be measured or observed without changing the identity or the composition of the substance. 

E.g. colour, odour, melting point, boiling point, density etc. 

The measurement or observation of chemical properties requires a chemical change to occur. e.g. Burning of Mg-ribbon in air 

Chemical properties are characteristic reactions of different substances; these include acidity or basicity, combustibility etc.Many properties of matter such as length, area, volume, etc., are quantitative in nature. Metric System was based on the decimal system. 

The International System of Units (SI) 

The International System of Units (in French Le System International d‘Unites– abbreviated as SI) was established by the 11th General Conference on Weights and Measures (CGPM from Conference Generale des Poids at Measures). The SI system has seven base units.