The International System of Units ( SI )
Prefixes in SI system
Multiple Prefix Symbol 10
-12 pico p
10 -9 nano n
10 -6 micro µ
10 -3 milli m
10 -2 centi c
10
-1 deci d 10 deca da 10 2 hecto h 10 3 kilo k 10 6 mega M 10 9 giga G
10
12 tera T
Mass and Weight-- Mass of a substance is the amount of matter present in it while weight is the force exerted by gravity on an object . The mass of a substance is constant whereas its weight may vary from one place to another due to change in gravity . The mass of a substance can be determined very accurately by using an analytical balance
Volume-- Volume has the units of ( length ) 3 . So volume has units of m 3 or cm 3 or dm 3 . A common unit , litre ( L ) is not an SI unit , is used for measurement of volume of liquids . 1 L = 1000 mL , 1000 cm 3 = 1 dm 3
Density : Density of a substance is its amount of mass per unit volume . SI unit of density = SI unit of mass / SI unit of volume = kg / m 3 or kg m – 3 This unit is quite large and a chemist often expresses density in g cm – 3 .
Temperature--There are three common scales to measure temperature — ° C ( degree celsius ), ° F ( degree Fahrenheit ) and K ( kelvin ). Here , K is the SI unit .