1. Units of Measurements and Uncertainty
Objectives:
1. Identify the metric units of measurement for length, mass, and volume.
2. List the common metric prefixes and demonstrate how metric prefixes can be used to change units
3. Explain why measuring always involves estimation.
4. Describe two causes of uncertainty in measurements.
5. Explain the difference between accuracy and precision.
Key Terms:
metric system, International System of Units (SI), base unit, mass, derived unit, volume, metric prefix, precision, accepted value, accuracy

2. Measurements are required for scientific inquiry
Measurements are required for scientific inquiry. In order to have meaning a unit must be attached to the measurement. Throughout the different scientific disciplines you will find the use of the metric system. Becoming familiar with the standard prefixes will make solving equations and converting units easier.

3. Metric Prefixes Prefix Prefix Symbol Meaning Scientific Notation exa-
1,000,000,000,000,000,000
1018
peta- P
1,000,000,000,000,000
1015
tera- T
1,000,000,000,000
1012
giga- G
1,000,000,000
109
mega- M
1,000,000
106
kilo- k
1,000
103
hecto- h
100
102
deka- da 10
101
meter 1
deci- d
0.1
10-1
centi- c
0.01
10-2
milli- m
0.001
10-3
micro-
10-6
nano- n
10-9
pico- p
10-12
femto- f
10-15
atto- a
10-18

4. SI Units The units used in science are those primarily used throughout the world. The International System of Units (SI) is a system based on the metric system. There are 7 fundamental units of measure
Name
Symbol
Unit of Measure
Unit Symbol
Unit Dimensions
length (distance)
l (d)
meter m
mass
kilogram kg
time t
second s
electric charge Q
coulomb C
temperature T
Kelvin K
amount of a substance n
mole
mol

5. English to Metric Conversions:
Distance
Mass
Volume
Pressure / Energy
Temperature
1km = 0.62 mi
1kg = 2.2lbs
3.744L = 1 gal
101,325Pa = 1atm
oC = 5/9 (oF-32)
1m = 39.37in
kg = 1ton
1 L = 1.06qt
4.184J = 1cal
oK = oC + 273
1m = yd
28.3g = 1oz
250ml = 1c
1cm = in
453.59g = 1lb

6. Other SI units derived from the base units
Name
Symbol
Unit of Measure
Unit Symbol
Unit Dimensions
acceleration a
meter per second squared
m/s2
area A
square meter m2
capacitance C
Farad F
C2*s2/kg*m2
density D
kilogram per cubic meter
kg/m3
electric current I
Ampere
C/s
electric field intensity E
Newton per coulomb
N/C
kg*m/C*s2
electric resistance R
Ohm d
kg*m2/C2*s
emf x
Volt V
kg*m2/C*s2
energy
Joule J
kg*m2/s2
force
Newton N
kg*m/s2
frequency f
hertz Hz
s-1
heat Q
illuminance
lumens per square meter lx
cd/m2
inductance L
Henry H
kg*m2/C2
luminous flux
lumen lm cd
magnetic flux
Weber Wb
kg*m2/C*s
magnetic flux density B
Tesla (weber per square meter) T
kg/C*s
potential difference
power P
Watt W
kg*m2/s3
pressure p
Pascal (Newton per square meter) Pa
kg/m*s2
velocity v
meters per second
m/s
volume
cubic meter m3
work

7. Some commonly used values in science.
Speed of light in a vacuum
x 108 m/s
Speed of sound
m/s (depending on temperature)
Acceleration due to Gravity
9.8 m/s2
Average Earth - Sun distance (1 AU)
1.50 x 1011 m
Average Earth - moon distance
3.84 x 108 m
Average radius of the Sun
6.96 x 108 m
Average radius of Jupiter
6.99 x 107 m
Average radius of Earth
6.37 x 106 m
Average radius of the moon
1.74 x 106 m
Average radius of the hydrogen atom
~5 x m
Mass of the Sun
1.99 x 1030 kg
Mass of Jupiter
1.90 x 1027 kg
Mass of Earth
5.98 x 1024 kg
Mass of the moon
7.35 x 1022 kg
Proton mass
x kg
Neutron mass
x kg
Electron mass
9.11 x kg
Atomic mass unit (amu)
x kg
Electron charge
1.6 x C
Avogadro's number
6.02 x 1023
Planck's constant (h)
x J-s
Gas constant (R)
atm-L/mol-K
Molar volume of gas
22.4L