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Define Mass and Weight. |
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Answer» The mass of a substance is constant whereas its weight may vary from one place to another due to the CHANGE in gravity. The mass of a substance can be determined very accurately in the laboratory by USING an analytical balance. ( see figure) The SI unit of mass is kilogram. Its fraction gram `(1kg=1000g)`, is used to laboratories due to the smaller amounts of chemicals used in chemical reactions.  Volume has the units of `("length")^(3)`. So in SI system, volume has units of `m^(3)`. But again, in chemistry laboratories, smaller volumes are used . Hence, volume is often denoted in `cm^(3)` or `dm^(3)` units. A common unit, litre (L) which is not an SI unit, is used for measurement of volume of liquids. `1 L = 1000 kL, 1000 cm^(3) = 1 dm^(3)`. To visualise these relations see figure:  In the laboratory, volume of liquids or solutions can be measured by graduated cylinder, burette, pipette etc. A volumetric flask is used to prepare a known volume of a solution. These MEASURING devices are SHOWN in figure. 
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