Introduction to physical chemistry/general chemistry (simple tool kits)
chemistry involves the separation and detailed examination of selected kinds of matter. in the study of chemistry, the relative quantities of matter and associated energy are measured.
THE METRIC SYSTEM
For a universal, unified and self consistent system of measuring units, the international system, commonly referred to as SI, after the initials of Systeme International was adopted. the metric system of measurement was defined for seven base units listed in the table below.
BASIC UNITS
BASIC QUANTITY
|
NAME
|
SYMBOL
|
Lenght
|
Metre
|
m
|
Mass
|
Kilogram
|
kg
|
Time
|
Second
|
s
|
Electrical Current
|
Ampere
|
A
|
Temperature
|
Kelvin
|
K
|
Amount of substance
|
mole
|
mol
|
Luminuos intensity
|
Candela
|
cd
|
Many important units with special names and symbols can be derived from the SI base units. examples of some SI-derived units, expressed in terms of base units, are shown below;
QUANTITY
|
DEFINITION
|
NAME OF DERIVED UNIT
|
UNIT SYMBOL
|
Area
|
Length x length
|
Square meter
|
M2
|
Volume
|
Area x length
|
Cubic metre
|
M3
|
Speed, Velocity
|
Distance per unit time
|
Metre per second
|
m/s
|
Acceleration
|
Change in speed per unit time
|
Meter per second squared
|
M/S2
|
Mass density
|
Mass per unit volume
|
Kilogram per cubic meter
|
Kg/m3
|
Energy
|
Force x distance
|
joule
|
J or kgm2/s2
|
Force
|
Mass x acceleration
|
Newton
|
N or kgm/s2
|
pressure
|
Force per unit area
|
pascal
|
Pa or N/M2
|
UNIT CONVERSION
During measurement, calculation involving different units occur and a quantity described in one unit can be converted to another equivalent quantity with a different unit using a conversion factor.
the conversion factor expresses the relationship between the two units and can be used in changing from one unit to the other using;
Original quantity X conversion factor = Equivalence quantity
several conversion factors between units common in physical chemistry are given below
1 foot = 12 inches
1 hour = 60 minutes
1 minute = 60 seconds
1 inch =2.54 cm
1 nm = 10
1 A (Angstrom) = 10-9 m = 10-7cm
1 erg (energy) = 10-7 J
1 eV (energy) = 1.602 x 10
1 dyn (force) = 10-5 J
1 calorie = 4.184 J
1 micron = 10-6 m = 1µm
for example to convert 69.5 inches to cm
the relationship between the two units is 1 inch = 2.54 cm and can be written as;
equivalence = 69.5 X 2.54 = 176.53 cm
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