Chapter 1:Unit 7. Metric System and SI System of Measurements

Metric and SI system of Units

Metric system is the oldest method of measurement. In each type of measurement, there is a base unit. The other units are related to the base unit by power of 10. These are called metric prefixes. The prefix of the unit name indicates if the unit is larger or smaller than the base unit.

Length is measured by determining the distance between two points. Mass is determined by the amount of matter in an object. Volume is determined by the amount of space occupied by a three -dimensional object.

Modern version of metric system is called International System of Units (SI).

Metric Base Units

The metric system uses the following base units:

Unit of Measurement          Name of Unit         Abbreviation

Length                                            Meter                              m or cm

Mass                                                Gram                              g

Volume                                           Liter                               L

Find below common metric prefixes.

Therefore 9 ml= 9/1000= 0.009 l(liter)

12 kg= 12*1000= 12000g

23 cm= 23/100= 0.23 m

Metric prefixes can be equally applied for SI units. Please find below common SI units.

SI Units

***The new definition of the kilogram sets it equal to the mass of 1.4755214 x 10⁴⁰ photons from a cesium atom.

Kelvin is defined in terms of Boltzman constant

Mol is defined in terms of Avogadro number 6.02214076 × 10²³ mol⁻¹.

Liter: It is a nonstandard metric unit. Liter is defined as volume of 0.1 m cube or 1 decimeter cube. A smaller non SI unit is often used to measure volume which is 1 milliliter. Since 1000ml = 1L and 1 L contains 1000 cm3, therefore 1 cm3= 1ml. Usually 1 cm3 is used for solid substances and 1 ml is used liquid substances.

Watch out this video and have fun!!!

Questions:

1. 1. What is the unit of length in metric system?
   2. 1 cc is the unit of what quantity?

Ans: 1. Meter

2.volume