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Common Unit Prefixes
Prefix Symbol Factor Example
femto f 10 −15 1 femtosecond (fs) = 1 × 10 −15 s (0.000000000000001 s)
pico p 10 −12 1 picometer (pm) = 1 × 10 −12 m (0.000000000001 m)
nano n 10 −9 4 nanograms (ng) = 4 × 10 −9 g (0.000000004 g)
micro µ 10 −6 1 microliter (μL) = 1 × 10 −6 L (0.000001 L)
milli m 10 −3 2 millimoles (mmol) = 2 × 10 −3 mol (0.002 mol)
centi c 10 −2 7 centimeters (cm) = 7 × 10 −2 m (0.07 m)
deci d 10 −1 1 deciliter (dL) = 1 × 10 −1 L (0.1 L )
kilo k 10 3 1 kilometer (km) = 1 × 10 3 m (1000 m)
mega M 10 6 3 megahertz (MHz) = 3 × 10 6 Hz (3,000,000 Hz)
giga G 10 9 8 gigayears (Gyr) = 8 × 10 9 yr (8,000,000,000 Gyr)
tera T 10 12 5 terawatts (TW) = 5 × 10 12 W (5,000,000,000,000 W)

Si base units

The initial units of the metric system, which eventually evolved into the SI system, were established in France during the French Revolution. The original standards for the meter and the kilogram were adopted there in 1799 and eventually by other countries. This section introduces four of the SI base units commonly used in chemistry. Other SI units will be introduced in subsequent chapters.


The standard unit of length    in both the SI and original metric systems is the meter (m)    . A meter was originally specified as 1/10,000,000 of the distance from the North Pole to the equator. It is now defined as the distance light in a vacuum travels in 1/299,792,458 of a second. A meter is about 3 inches longer than a yard ( [link] ); one meter is about 39.37 inches or 1.094 yards. Longer distances are often reported in kilometers (1 km = 1000 m = 10 3 m), whereas shorter distances can be reported in centimeters (1 cm = 0.01 m = 10 −2 m) or millimeters (1 mm = 0.001 m = 10 −3 m).

One meter is slightly larger than a yard and one centimeter is less than half the size of one inch. 1 inch is equal to 2.54 cm. 1 m is equal to 1.094 yards which is equal to 39.36 inches.
The relative lengths of 1 m, 1 yd, 1 cm, and 1 in. are shown (not actual size), as well as comparisons of 2.54 cm and 1 in., and of 1 m and 1.094 yd.


The standard unit of mass in the SI system is the kilogram (kg)    . A kilogram was originally defined as the mass of a liter of water (a cube of water with an edge length of exactly 0.1 meter). It is now defined by a certain cylinder of platinum-iridium alloy, which is kept in France ( [link] ). Any object with the same mass as this cylinder is said to have a mass of 1 kilogram. One kilogram is about 2.2 pounds. The gram (g) is exactly equal to 1/1000 of the mass of the kilogram (10 −3 kg).

The photo shows a small metal cylinder on a stand. The cylinder is covered with 2 glass lids, with the smaller glass lid encased within the larger glass lid.
This replica prototype kilogram is housed at the National Institute of Standards and Technology (NIST) in Maryland. (credit: National Institutes of Standards and Technology)


Temperature is an intensive property. The SI unit of temperature is the kelvin (K)    . The IUPAC convention is to use kelvin (all lowercase) for the word, K (uppercase) for the unit symbol, and neither the word “degree” nor the degree symbol (°). The degree Celsius (°C)    is also allowed in the SI system, with both the word “degree” and the degree symbol used for Celsius measurements. Celsius degrees are the same magnitude as those of kelvin, but the two scales place their zeros in different places. Water freezes at 273.15 K (0 °C) and boils at 373.15 K (100 °C) by definition, and normal human body temperature is approximately 310 K (37 °C). The conversion between these two units and the Fahrenheit scale will be discussed later in this chapter.

Questions & Answers

who are the alchemist?
Victor Reply
alchemy science of transmutation. typically it is aim at tranforming lead to or other base metals to gold and the creation of the philosophers stone which in reality isn't a stone it's something priceless something we all need for coming times. don't be fooled
read Corinthians 5 verses 50 to the end of the chapter then read revelations chapter 2 verse 17
The word "Alchemy" comes from the forgotten name for Ancient Egypt, Khemmet. Khem was the name for the Egyptian Empire, but the actual land of Egypt was called Khemmet because the "T" on the end of a word denoted a physical location on Earth and not just an idea.
What's the mass number of carbon
Charlie Reply
first Faraday's law
mass number of carbon is 12.
wat d atomic number of oxygen
atomic number of oxygen is 8
which quantum number divides shell into orbitals?
Tomiwa Reply
what is atom
Desmond Reply
an atom is a smallest indivisible part of an element
an atom is the smallest part of an element that takes part in a chemical reaction
wat is neutralization
Dubem Reply
when any acid reacts with base to decrease it's acidity or vice-versa to form salt and solvent.. which is called neutralization
explain buffer
buffer is a solution which resists changes in pH when acid or alkali added to it..
hello, who is online
buffer is the solution which resist the change in pH by addition of small amount of acid or alkali to it
neutralisation is the process of mixing of a acid and a base to form water and corresponding salt
how to solve equation on this
Princewill Reply
what are the elent of ionic and covalent bonding
what is gases
Wesike Reply
Its one of the fundamental sate of matter alone side with liquid, solid and plasma
What is chemical bonding
To my own definitions. It's a unit of measurement to express the amount of a chemical substance.
Ozoaniehe Reply
What is mole
It's the unit of measurements used to express the amount of chemical substance.
What is pressure
Stellamaris Reply
force over area
force applied per unit area
force applied per unit area
Why does carbonic acid don't react with metals
Aditya Reply
Why does carbonic acid don't react with metal
Some metals will react depending on their Standard Electrode Potential. Carbonic acid is a very weak acid (i.e. a low hydrogen ion concentration) so the rate of reaction is very low.
sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Emokiniovo Reply
a sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Sharmin Reply
an object of weight 10N immersed in a liquid displaces a quantity of d liquid.if d liquid displaced weights 6N.determine d up thrust of the object
ugonna Reply
how human discover earth is not flat
Jason Reply
We don't fall off. If set off in any direction in a straight line and keep going. You'll end up back where you started.
earth is spherical
Also, every other planet is spherical as that is the most energy efficient shape. gravity pulls equally on all areas. Sphere.

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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