Basic chemistry

              UNITS OF MEASUREMENT       Many  properties of matter are quantitative in nature.  When you measure something, you are  comparing it with some standard. The standard  quantity is reproducible and unchanging.       Many properties of matter such as mass,  length, area, pressure, volume, time, etc.  are quantitative in nature. Any quantitative  measurement is expressed by a number  followed by units in which it is measured.  For example, length of class room can be  represented as 10 m. Here 10 is the number and  'm' denotes metre-the unit in which the length  is measured. The standards are chosen orbitrarily  with some universally acceped criteria. ''The  arbitrarily decided and universally accepted  standards are called units.''      There are several systems in which units  are expressed such as 1.C.G.S. System  :Length (centimetre), Mass (gram), Time (second) 2.M.K.S. System : Length (metre), Mass (kilogram), Time  (sec