Notes 1 Measurement
Name_______________________________
Date___________ Block________
When we MEASURE, we determine the dimensions, volume, or quantity of something.
Dimensions such as height, width, and length are used to determine the size of an object.
For example: a room may be 10.0 meters wide, 20.0 meters long, and 3.0 meters high.
Volume refers to how space the object takes up.
For example: You may pour 250.0 milliliters or 1.0 liter of water.
Quantity can be how many or how much. “How many” is used when you can count things, such
as 25 apples. “How much” is used when you can’t count the thing(s) and you determine the
mass of the object, such as 25.0 grams of aluminum. In chemistry, we usually mean “how
much” when we say quantity.
These measurements are often called “quantitative measurements” because numbers are used.
Quantitative measurements involve using an instrument or tool such as a metric ruler for
distances, a graduated cylinder for volume, and a balance for mass. For counting things, we
usually just use our brain to keep track of how many, but there are times when we might have to
use a “counter” – a tool that keeps track of how many.
Quantitative measurements not only use numbers but UNITS as well. No numerical
measurement is ever given without a unit or label.
In science, we use the metric system (a.k.a, Systéme Internationale d’Unités, or SI). Everything
is based on powers of 10. There is a base unit and then different prefixes are used to indicate the
power of 10. For example, in length, the base unit is the meter. One-tenth of meter would called
a decimeter, one one-hundredth of a meter would be a centimeter, etc. There are some non-SI
units that we also use for certain quantities.
QUANTITY
length
mass
volume
time
temperature
how much
of a substance
pressure
energy
BASE UNIT
meter
kilogram
cubic meter
second
kelvin
SI UNIT
Non-SI Unit and
ABBREVIATION
Symbol
m
kg
m3
liter (L)
s
K
degree Celsius (oC)
mole
pascal
mol
Pa
joule
J
atmosphere (atm)
millimeter of
mercury (mmHg)
calorie (cal)
The most common prefixes used in measurements are:
PREFIX
kilodeci-
SYMBOL
k
d
centi-
c
milli-
m
micro-
μ
MEANING
1 000 or 10 times larger than the unit it precedes
10 times smaller than the unit it precedes ; or 1/10 of the unit it
precedes
100 times smaller than the unit it precedes; or 1/100 of the unit
it precedes
1000 times smaller than the unit it precedes; or 1/1000 of the
unit it precedes
1 million times smaller than the unit it precedes; or 1/1 000 000
of the unit it precedes
3
For example, using the SI symbol for length:
UNIT
kilometer
meter
(base unit)
decimeter
centimeter
millimeter
micrometer
EXAMPLES
SYMBOL RELATIONSHIP
(APPROXIMATE VALUES)
km
1 km = 103 m
length of 5 city blocks ≈ 1 km
m
dm
cm
mm
μm
1m = 1m
101 dm = 1 m
102 cm = 1 m
103 mm = 1m
109 μm = 1 m
height of door knob from floor ≈ 1 m
diameter of large orange ≈ 1 dm
width of shirt button ≈ 1 cm
thickness of a dime ≈ 1 mm
thickness of RNA molecule ≈ 1μm
A reminder about powers of 10:
1 000 000
100 000
10 000
1 000
100
10
1
=
=
=
=
=
=
=
106
105
104
103
102
101
100
0.000 001
0.000 01
0.000 1
0.001
0.01
0.1
1
=
=
=
=
=
=
=
10 -6
10 -5
10 -4
10 -3
10 -2
10 -1
100