Conversion flow chart
Conversion of units:
Mass(m): The mass of a physical quantity is expressed in kilograms (kg), grams (gm), milligrams (mg),
pounds (lb), ounce (oz), tons etc. Some of the conversion factors of mass are given below:
1 kilogram = 1000 gm
1 gram = 1000 mg or 10−3 kg
1 milligram = 10−3 gm or 10−6 kg
1 pound = 453.59 gm or 0.45359 kg
1 ounce = 28.349 gm or 0.028349 kg
The chemist do come across many conversion factors during calculations
Volume(V): The volume of a liquid or a solution is expressed in gallons, liters (L), milliliters (mL), cubic meters (m3), cubic centimeters (cm3), cubic decimeter (dm3) etc. The conversion factors used are given below:
1 liter = 1000 mL = 103mL = 10−3 m3
1 milliliter = 10−3L = 10−6 m3
1 m3= 1000 L = 106 mL
1 cm3 = 10−3 L = 1 mL
1 dm3 = 10−3 m3 = 1 L
A chemist needs 30 kg of ethyl alcohol for a synthesis. If the density of the alcohol is 0.789 g/ml, how many
liters of alcohol is used?
Solution: Volume = Mass / density
For getting the answer the quantities of mass and density should be in same units.
Conversion factor : 1000g = 1 kg
| ∴30 kg of alcohol | = | 30×1000 g of alcohol |
| = | 3 × 104 g | |
| ∴Volume of the alcohol | = | 3×104 g / 0.789 g/ml |
| = | 38022 ml. |
The answer should be in liters.
| Conversion factor: 1000 ml | = | 1 liter |
| ∴Volume of the alcohol | = | 38022/1000 ml |
| = | 38.02 liters. |
Worked out example
Calculate the mass of 65.0 cm3 of water in kilograms (Density of water is 1 g/cm3)
Solution:
| Mass | = | Volume × density |
| = | 65.0 cm3 × 1 g/cm3 | |
| = | 65 g | |
 |
Length(l):The length of an object is expressed in meters (m), millimeters (mm), centimeters(cm), inches (in.), yards (yd), miles (mi), angstroms (Å) etc. Following are the conversion factors for length:
1 meter = 100cm = 1000mm
1 centimeter = 10−2m = 10 mm
1 millimeter = 0.1 cm = 0.001 m
1 inch = 25.4mm = 2.54 cm = 0.0254m
1 feet = 12 inches
1 yard = 3 foot
1 mile = 8 furlong = 5280 feet
1 angstrom (Å)= 10−8cm = 10−10m = 0.1 nm
Usually, Å units are used for wave length(λ) calculations.
Density (d or ρ): The density of a substance is expressed as gram per cubic centimeter (g/cm3), kilogram per cubic meter (kg/m3), gram per liter (g/L), pounds per cubic inch (lb/in3) etc. Following are the few conversion factors:
1 g/cm3 = 103 kg/m3 = 0.036 lb/in3
1 kg/m3 = 1 g/L = 10 − 3 g/cm3 = 3.6 × 10 − 5
lb/in3
1 lb/in3 = 2.76 × 104 kg/m3 = 27.6 g/cm3
Worked out example
Calculate where the magnitude of Fahrenheit and Centigrade temperature are same?
Solution: From the given problem consider X°C = X°F
−40°C = −40°F.
At −40°C, Celsius scale = Fahrenheit scale.
Temperature (T):
The temperature of any substance is expressed in Kelvin (K),
degree Celsius (°C), degrees Fahrenheit (°F). The conversion factors for temperature are given below:
Fahrenheit to Celsius:
Celsius to Fahrenheit: °F = (1.8 × °C) + 32
Celsius to Kelvin: K = °C + 273
Pressure(P):
The pressure of a gas has units of millimeter of Hg (mm Hg), pascals (Pa),
pounds per square foot (psf), pounds per square inch (psi), torr etc., The conversion factors are:
1 mm of Hg = 133.3 Pa = 1 torr
1 pascal = 0.0075 mm Hg = 0.0075 torr
1 psf = 0.359 torr
1 psi = 144 psf = 51.71 torr
1 torr = 1 mm Hg
| Prefix | Factor | Symbol | Prefix | Factor | Symbol |
| yotta | 1024 | Y | deci | 10−1 | d |
| zeta | 1021 | Z | centi | 10−2 | c |
| exa | 1018 | E | milli | 10−3 | m |
| peta | 1015 | P | micro | 10−6 | μ |
| tera | 1012 | T | nano | 10−9 | n |
| giga | 109 | G | pico | 10−12 | p |
| mega | 106 | M | Femto | 10−15 | f |
| kilo | 103 | k | atto | 10−18 | a |
| hecto | 102 | h | zepto | 10−21 | z |
| deka | 101 | da | yocto | 10−24 | y |
Energy, heat and work (E, Q, W):
The units of energy are joules (J), kilo joules (kJ), calories (cal), kilo calories (kCal), electron volt (eV) etc.
The conversion factors of energy, heat and work include:
1 joule = 2.38 × 10−4 kCal = 10−3 kJ
1 kCal = 4.184 kJ = 4184 J
1 Cal = 4.184 J = 10−3 kCal
1 J = 107 ergs
1 eV = 1.602 × 10−19 J = 1.602 × 10−22 kJ
Concentration (C):
The concentration of a solution is expressed in units of moles per
liter or molarity (mol/L or M), parts per million (ppm), parts per billion (ppb) etc.
