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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.

Length

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.

Mass

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

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

what's kinetic energy
Charity Reply
what is anion?
Hussniz Reply
an anion is a positively charge ion
ade
Thnkz
Hussniz
an anion is a negatively charged ion
Johnson
And anion is a negatively charged ion which move towards the anode which is positively charged.
Ngwesse
what is matter
Henry Reply
what is pressure
Henry
what is water?
Scarcies Reply
hydrogen gas burned into oxygen gas which forms a polar molecule, has a defenate shape volume but not shape. at 20 degrees Celsius exists as an aqueous solution. Is a solvent that dissolves many solutes into solution. And can act as an acid or a base.
David
HOW CAN ETHANOL BE PREPARED FORM CASSAVA.... (WITH EQUATION)
Obi Reply
by mixing
Henry
it is less dense than water
Erastus Reply
can cooking gas be durable in gallon. ..
mowete
no
PRINCESS
reason pls
mowete
What is happening
Oluchi Reply
Why does ice float on water?
Ngwesse
As it cools, olive oil slowly soldifies and froms a solid over a range of temperatures. Which best describes the solid?
Tammie Reply
definition of a sample
ashley Reply
a small part or quantity intended to show what the whole is like
Abdull
What does kj stand for ? or just k. example - 371K
Katr Reply
kilojoules or Kelvin
Annie
what is atom
divinegift Reply
atom is anything that has weight and can occupy space
Neutons
atom is the smallest particle of an element that can neitherbe divided nor destroyed
clin
atom is the smallest indivisible particle of an element.
Igbayima
atom is the smallest particle of an element that can neither be created,subdivided or destroyed
Gbolahan
All wrong
Gift
Do you know that atoms can further be devided
Gift
Go and read 📘 up Dalton atomic theory and who disproved.. Read 📘 up atomic theory
Gift
an atom is the smallest particle of an element that can take part in a chemical reaction
Anyebem
good@anyebem
Henry
what is anion?
Hussniz
what is a structure of atomic
Deren Reply
WATS atomic structure?
mowete
what is the meaning of intermolecular force
Eunice Reply
is the force of attraction that exist between two or more molecules
Johnson
What is a primary standard solution ?
Duval
a known solution
Fiko
Characteristic of a primary standard solution
Duval
pauli's exclusion is based on what?
avdhesh Reply
quantum theory
Charles
What is greatest modification made in dalton's atomic theory?
Ngwesse Reply

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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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