Ch. 2 Sec. 1
Measures in Science
Metric System & SI Units
 French Scientists adopted metric system in 1795
 Metric system uses powers of 10
 10 millimeter = 1 centimeter
 10 centimeter = 1 decimeter
 10 decimeter = 1 meter
 There are 7 base units
Base units Chart
Base Quantity
Length
Mass
Time
Temperature
Amount of Substance
Electric Current
Luminous Intensity
SI Base Units
Base Unit
Meter
Kilogram
Second
Kelvin
Mole
Ampere
Candela
Symbol
m
kg
s
K
mol
A
cd
Derived units
 Combination of the base units
 Speed or velocity = meters per second, m/s
 Energy = joule, kg m2/s2
SI Unit Prefixes
Prefix
Symbol
Multiplier
Sci. Notation
Pico
p
1/1,000,000,000,000
10-12
Nano
n
1/1,000,000,000
10-9
Micro
µ
1/1,000,000
10-6
Milli
m
1/1,000
10-3
Centi
c
1/100
10-2
Deci
d
1/10
10-1
Kilo
k
1000
103
Mega
M
1,000,000
106
Giga
G
1,000,000,000
109
Tera
T
1,000,000,000,000
1012
Scientific Notation
 Able to make using really large or small numbers easier
 Expressing decimal numbers in powers of 10
 N x 10n
 Move decimal point until only one non-zero digit remains
 Count the number of spaces and use that as exponent
 Earth to Mars = 227 800 000 000m
 2.278 x 1011m
 Mass of electron = 0.000 000 000 000 000 000 000 000 000 000 911
kg
 9.11 x 10-31kg
Express in Sci. Notation
 5800
 450 000
 302 000 000
 86 000 000 000
 0.000 508
 0.000 000 45
 0.0003600
 0.004
Express in Sci. Notation
 5800 = 5.8 x 103
 450 000 = 4.5 x 105
 302 000 000 = 3.02 x 108
 86 000 000 000 = 8.6 x 1010
 0.000 508 = 5.08 x 10-4
 0.000 000 45 = 4.5 x 10-7
 0.0003600 = 3.600 x 10-4
 0.004 = 4 x 10-3
Converting Units
 What is the equivalent in km of 670 m?
 1 km = 1000 m
 (1000 m)/ (1 km) = 1
 Using a Conversion Factor you can determine the
relationship between two units
 Multiplier equal to one
 670 m = (670 m) (1 km / 1000 m)
 (670 m x 1 km) / 1000 m = 0.670 km
 Label units will cancel out
Converting Units Practice
 1.1 cm  meters
 76.2 pm  millimeters
 2.1 km  meters
 2.278 x 1011 m  kilometers
 147 g  kilograms
 11 Mg  kilograms
 7.23 µg  kilograms
 478 mg  kilograms
Converting Units Practice
 1.1 cm  1.1 x 10-2 m
 76.2 pm  7.62 x 10-8 mm
 2.1 km  2.1 x 103 m
 2.278 x 1011 m  2.278 x 108 km
 147 g  1.47 x 10-1 kg
 11 Mg  1.1 x 104 kg
 7.23 µg  7.23 x 10-9 kg
 478 mg  4.78 x 10-4 kg
Adding and Subtracting in Sci. Notation
 When adding or subtracting, make sure the powers of 10 are
the same (10N)
 4 x 108 + 3 x 108
 (4 + 3) x 108
 7 x 108
 (4.1 x 10-6) – (3.0 x 10-7)
 (4.1 x 10-6) – (0.30 x 10-6)
 (4.1 – 0.30) x 10-6
 3.8 x 10-6
Multiplying & Dividing in Sci. Notation
 Multiply or divide the values and the units
 Add (if multiplying) or subtract (if dividing) the exponents
 (4 x 103 kg)(5 x 1011 m)
 (4 x 5) x 103 + 11 kg•m
 20 x 1014 kg m  2 x 1015 kg m
 (8 x 106 m3) / (2 x 10-3 m2)
 (8/2) x 106 – (-3) m(3-2)
 4 x 109 m
 If units have powers, add or subtract accordingly