3 Mass Mass is the quantity of matter which an object contains. It is a scalar quantity. Weight is a force; it is the gravitational pull of the earth on an object. SI unit of weight is thus newton. The standard unit of mass is the kilogram. The kilogram is the mass of a particular cylinder of platinum-iridium alloy. The cylinder is kept at the International Bureau of Weights and Measures at Sevres, near Paris. Sub multiples are: 1 microgram = 1µg = 10−6g = 10−9kg (mass of a very small dust particle) 1 milligram = 1mg = 10−6kg 1 gram = 1g = 10−3kg (mass of a grain of salt) (mass of a paper clip) The mass of an object remains the same everywhere, but the weight of an object varies from place to place across the surface of the earth. The weight of an object increases slightly as we go from the equator to the poles. Weight also decreases as we go further away from the surface of the earth. Chemical balance, lever balance and some direct reading balances are used to measure the mass of an object. Spring balance is used to measure the weight of an object.