Properties of matter and their measurements

Chemistry is an experimental science . An experiment always involves observation of a phenomenon under certain set of conditions. The Qualitative scientific observation generally required the measurements of one or more physical quantities such as mass, length, density,volume, pressure, temperatures etc.

                               A physical quantity is expressed in the term of a number and a unit. Without unit the number has no meaning, for example :- the distance between two points is "4" has no meaning unless a specific unit (inch, centimeter, meter etc) is associated with the number. The unit of physical quantity depends on three basic units, ie; unit of mass, length and time. Since these are independent units, which do not derived from any other units, so they are called fundamental units.

 

Today we have 7 fundamental units or basic units. All other units were derived from these basic units, so all other units are called as Derived units. Examples of derived units are area, volume, force, density, work etc.

Unit system

Various system of units were in use prior to 1960.

The common one are the following

FPS system 

Three basic units are foot, pound and second. This is a english system basically used in english countries like England.

CGS system

Three basic units are centimeter, gram, second. This is decimal system used in France.

MKS system

Three basic units are meter, kilogram, second. This is decimal system used in France. This is also called metric system.

MKS system often known as metric system was very popular through out the world, but the drawback with the system was that a number of different metric units for the same quantity were used in different part of the world. In 1964, the "National bureau of standards" adopted a slightly modified version of the metric system which has been officially recommended in 1960 by an international body, "Genral conference of weight and measure". This revised set of units known as  International system of unit(SI unit)

Now the SI units have been accepted by scientist all over the world in all branches of science.

International system of unit(SI unit)

SI unit system has 7 basic units, this is modification of MKS system in which some other basic units were added. This 7 basic units along with their symbols were tabulated below:-

physical quantities	basic units	symbols
Length	meter	m
Mass	kilogram	Kg
Time	second	S
Temperature	kelvin	K
Current	ampere	amp or A
Luminous intensity	candela	Cd
Amount of substance	mole	Mol

Sometimes sub multiples and multiples are used to reduce or enlarge the size of different units. 

Sub multiples

slno.	submultiples	symbols	values
1	deci	d	10⁻¹
2	hecto	H	10⁻²
3	kilo	K	10⁻³
4	mega	M	10⁻⁶
5	giga	G	10⁻⁹
6	tera	T	10⁻¹²
7	peta	P	10⁻¹⁵
8	exa	E	10⁻¹⁸
9	zeta	Z	10⁻²¹
10	yotta	Y	10⁻²⁴

These submultiples can be remembered by the help of a hindi line.

DC को milli micro nano pic खींचा femto ने आया atto जैसा देखा zepto yocto ने।

Values of power :- first three negative power  is 123 then power become table of 3 

(3×2=6,3×3=9,3×4=12,3×5=15,3×6=18,3×7=21,3×8=24)

Multiples

slno.	multiples	symbols	values
1	deca	D	10¹
2	hecto	H	10²
3	kilo	K	10³
4	mega	M	10⁶
5	giga	G	10⁹
6	tera	T	10¹²
7	peta	d	10¹⁵
8	exa	d	10¹⁸
9	zeta	d	10²¹
10	yotta	Y	10⁻²⁴

These multiples can be remembered by the help of a hindi line.

DHK mega और Giga Teta Pata पूूूछ रहे थे, Exa ने Zeta Yotta बता दिया।

Values of power :- first three positive power  is 123 then power become table of 3 

(3×2=6,3×3=9,3×4=12,3×5=15,3×6=18,3×7=21,3×8=24)

Some Greek alphabet used in measurements

1. Alpha -  ∝
2. Beta-  β
3. Gamma-  y
4. Delta-  δ
5. Epsilon- ε
6. Zeta-  ኢ
7. Eta-  η
8. Nu-  V
9. Pie- π
10. Rho- ρ
11. Kappa-  K
12. Lambda- λ
13. Phi-  ф
14. Chi-  χ
15. Psi-  ψ