Units of Measurement
2.2
Definitions
 Weight –measure of the gravitational
pull on matter
 Diff between mass and weight
 Quantity – something that has
magnitude, size or amount
 Every measurement must have a unit
 SI-Le Système International d’Unitès
 We use 7 base units and prefixes to
express all units
Quantity
Length
Symbol Unit
l
Meter
Abbreviation
m
Mass
m
Kilogram kg
Time
t
Second
s
Thermodynamic
Temperature
Amount of a
Substance
Electric Current
Luminous
Velocity
T
Kelvin
k
n
Mole
mol
I
Iυ
Ampere
Candela
A
cd
 Mega - M 1 000 000 (b.u.) = 1M(b.u.)
 Kilo - k 1 000 (b.u.) = 1k(b.u.)
 hecto - h  100 (b.u.) = 1h(b.u.)
 deka - da  10 (b.u.) = 1da(b.u.)
Base Unit
 deci - d  10 d(b.u.) = 1 (b.u.)
 centi - c 100 c(b.u.) = 1 (b.u.)
 milli - m 1 000 m(b.u.) = 1 (b.u.)
 micro - µ 1 000 000 µ(b.u.) = 1 (b.u.)
 nano - n1 000 000 000 n(b.u.)=1 (b.u.)
Derived Units
 Combination of SI base units
 Examples – m3, g/cm3, kg/mol
 Volume – the amount of space
occupied by an object
 1000mL = 1 L = 1000cm3
Conversion Factors
 Ratio derived from the equality b/t 2
different units that can be used to
convert from 1 unit to another
 Ex: there are 4 quarters in 1 dollar
 Dimensional analysis – math
technique that allows you to use
units to solve problems involving
measurments
Conversion Factors
 Quarters and dollars conversion
factor – 4 quarters = 1 dollar
 Convert 18 quarters to dollars
 Start with what you know
 What you are going to goes in the
top and coming from goes in the
bottom
 Convert 3 dollars to quarters
Conversions
 Convert 45 minutes to hours.
 Convert 2.5 hours to minutes.
 Convert 100 millimeters to
meters
 1 meter = 1000millimeters
 Convert 3 hours to seconds
Conversions
 Convert 0.12 kg to mg
 Must convert to base unit first if
going from one side to the other.
 Convert 130 cm to Mm
Conversions with Derived Units
 Convert 60 miles/hour to
kilometers per second
 1 mile = 1.609 kilometers
 How many grams per milliliter are
there in 34 kilograms per liter
Density
 The ratio of mass to volume
D = m
Know this
v
equation!!!
 Typically expressed as g/cm3.
 Predict the order of the following from
the most dense to the lease dense…
 Milk, mercury, gasoline, ice, a
diamond, a cork
Density
 Silver Bracelet
 Mass is 100.0 g and when it
displaces water, volume is 20.5
cm3
 Density of silver is 10.5 g/cm3
 Is this a silver bracelet?
Density Calculations
 A piece of an unknown material
has a mass of 5.85 g and a
volume of 7.57 cm3. What is the
density of the material?
Density Calculations
D = m
v
 D = m = 5.85 g
v
7.57 cm3
 Density = 0.77 g/cm3
Density calculations
 A 200 g piece of metal has a volume
of 25 cm3. Calculate the density of
the metal.
 An unknown mass of silicon
occupies a volume of 350 cm3.
Calculate the mass of Si knowing
that the density of Si is 2.34 g/cm3.
Density
 What is the volume that a 50
gram piece of gold occupies?
The density of gold is
19.30g/cm3.
Density
 A block of lead with dimensions of
2.0dm x 8.0cm x 35mm, has a
mass of 6.356kg. Calculate the
density of lead in g/cm3.
Density
 A flask weighs 345.8 g and is
filled with 225 mL of carbon
tetrachloride. The weight of the
flask and carbon tetrachloride is
found to be 703.55 g. Calculate
the density in g/ml and g/L
Density
 A 28.5 g of iron shot is added to a
graduated cylinder containing
45.5 mL of water. The water level
rises to the 49.1 mL mark.
Calculate the density.
Density
 A cylindrical tube of length 27.75
cm and radius of 2.00 cm is filled
with argon gas. The empty tube
weighs 188.25g. The tube filled
with argon weighs 188.87g .
Calculate the density.
Assignment
 Complete the section review on
page 42 and do numbers 1-5.
 This is due tomorrow!