http://www.ck12.org Chapter 3. Measurement
MEDIA
Click image to the left for more content.As the video suggests, chemistry is a discipline in which we study things that are very, very small. We measure
things like the size of an atom, which is approximately 1/10000000000 of a meter. Because individual atoms are so
small, the substances that we can actually see and study, even something as small as a drop of rain, are comprised
of an incredibly large number of atoms. There are literally thousands of billions of billions of particles in a drop
of water. In both of these examples, we expressed size in terms of fractions or multiples of the number 10. When
describing very small or very large physical quantities, we use prefixes to write the unit as a power of 10.Table3.3
displays most of these prefixes.
TABLE3.3: Commonly Used SI Prefixes
Prefix Meaning Abbreviation Numeric value Exponential
Notation
exa- billion billion E 10000000000000000001018
peta- thousand trillion P 1000000000000000 1015
tera- trillion T 1000000000000 1012
giga- billion G 1000000000 109
mega- million M 1000000 106
kilo- thousand k 1000 103
hecto- hundred h 100 102
deka- ten da 10 10
n/a one n/a 1 100
deci- one tenth d 0.1 10 −^1
centi- hundredth c 0.01 10 −^2
milli- thousandth m 0.001 10 −^3
micro- millionth μ 0.000001 10 −^6
nano- billionth n 0.000000001 10 −^9
pico- trillionth p 0.000000000001 10 −^12
femto- f 0.000000000000001 10 −^15
atto- a 0.000000000000000001 10 −^18The Relative Size of Things
We can express the relative size of things with which we are familiar. For instance, theFigure3.1 shows the height
of a human as measured in meters, or 10^0 scale. We see a dust mite, measured in micrometers –10−^6 scale; and a
virus, measured in nanometers –10−^9 scale. These are examples of length related to relative size and scale.