– , or cd sr kg – m – s , where the kilogram, metre and second are defined in terms of h, c and V Cs . Fig. . Analytical balance .
. 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. You should be careful in using these terms.
The mass of a substance can be determined accurately in the laboratory by using an analytical balance (Fig. . ). The SI unit of mass as given in Table .
is kilogram. However, its fraction named as gram ( kg = g), is used in laboratories due to the smaller amounts of chemicals used in chemical reactions. . .
Volume Volume is the amont of space occupied by a substance. It has the units of (length) . So in SI system, volume has units of m . But again, in chemistry laboratories, smaller volumes are used.
Hence, volume is often denoted in cm or dm units. A common unit, litre (L) which is not an SI unit, is used for measurement of volume of liquids. L = mL, cm = dm Fig. .
helps to visualise these relations. Fig. . Different units used to express volume Table .
Prefixes used in the SI System Multiple Prefix Symbol – – – – – – – – – – yocto zepto atto femto pico nano micro milli centi deci deca hecto kilo mega giga tera peta exa zeta yotta y z a f p n µ m c d da h k M G T P E Z Y In the laboratory, the volume of liquids or solutions can be measured by graduated