Chapter 2
Section 2
Section 2 Objectives
• Be able to define: quantity, measurement,
standard, length, mass, weight, derived unit,
volume, density, conversion factor.
• Be able to state the units of mass, length,
temperature, and time in the SI system
• Be able to explain the difference between
mass and weight.
Section 2 Objectives
• Be able to state the meaning of common
prefixes used in the SI system (Deka-, Hecto-,
Kilo-, Mega-, Giga-, deci-, centi-, milli-, micro-,
nano-.
• Be able to convert units within the SI system.
Section 2: Units of Measure
• Measurements are quantitative information.
• Measurements _______________ quantities.
• A quantity is something that has __________________,
__________, or ________________.
• A quantity is not the same as a measurement.
• Example: A teaspoon is a unit of measurement for
volume (a quantity)
• Nearly every measurement is a number plus a
___________.
Section 2: Units of Measure
• Measurements are quantitative information.
• Measurements represent quantities.
• A quantity is something that has __________________,
__________, or ________________.
• A quantity is not the same as a measurement.
• Example: A teaspoon is a unit of measurement for
volume (a quantity)
• Nearly every measurement is a number plus a
___________.
Section 2: Units of Measure
• Measurements are quantitative information.
• Measurements represent quantities.
• A quantity is something that has magnitude, size, or
amount.
• A quantity is NOT the same as a measurement.
• Example: A teaspoon is a unit of measurement for
volume (a quantity)
• Nearly every measurement is a number plus a
___________.
Section 2: Units of Measure
• Measurements are quantitative information.
• Measurements represent quantities.
• A quantity is something that has magnitude, size, or
amount.
• A quantity is NOT the same as a measurement.
• Example: A teaspoon is a unit of measurement for
volume (a quantity)
• Nearly every measurement is a number plus a unit.
Section 2: Units of Measure
• Scientists all over the world have agreed on a single
measurement system, ____________.
• These units are defined in terms of standards of
______________________________.
• International organizations monitor the defining
process, such as the ____________________
________________ ___ __________ ____
____________________ in the United States.
Section 2: Units of Measure
• Scientists all over the world have agreed on a single
measurement system, SI.
• These units are defined in terms of standards of
______________________________.
• International organizations monitor the defining
process, such as the ____________________
________________ ___ __________ ____
____________________ in the United States.
Section 2: Units of Measure
• Scientists all over the world have agreed on a single
measurement system, SI.
• These units are defined in terms of standards of
measurement.
• International organizations monitor the defining
process, such as the ____________________
________________ ___ __________ ____
____________________ in the United States.
Section 2: Units of Measure
• Scientists all over the world have agreed on a single
measurement system, SI.
• These units are defined in terms of standards of
measurement.
• International organizations monitor the defining
process, such as the National Institute of Standards
and Technology (NIST) in the United States.
Section 2: Units of Measure
For example, the number seventy five thousand
is written ___________________ instead of
____________________________ because the
comma is used in other countries to represent a
decimal point
Section 2: Units of Measure
For example, the number seventy five
thousand is written 75 000 instead of
75,000 because the comma is used in other
countries to represent a decimal point
SI System
• The SI system defines 7
base units for
1. length,
2. mass,
3. time,
4. temperature,
5. amount of a substance
SI Base Units
Quantity
Quantity Symbol
Unit name
Unit abbreviation
1.
Length
l
Meter
m
2.
Mass
m
Kilogram
kg
3.
Time
t
Second
s
4.
Temperature
T
Kelvin
K
5.
Amt of Subst.
n
Mole
mol
SI Base Units: Mass
• Mass is the measure of the ______________
____ ________________.
• The ___________, g, is 1/1000 of a kilogram
and is more useful for measuring masses of
small objects such as flasks and beakers.
• For even smaller objects, such as tiny
quantities of chemicals (think: medicines or
vitamins!), the _____________ or ____ is used.
SI Base Units: Mass
• Mass is the measure of the quantity of
matter.
• The gram, g, is 1/1000 of a kilogram and is
more useful for measuring masses of small
objects such as flasks and beakers.
• For even smaller objects, such as tiny
quantities of chemicals (think: medicines or
vitamins!), the milligram or mg is used.
• 1 milligram = 1/1000 of a gram
SI Base Units: Mass
• The measure of the gravitational pull on
matter (gravity) is _______________.
• Mass does not depend on ____________.
• As the force of Earths’ gravity on an object
increases, the object’s weight
_____________________.
• The weight of an object on the moon is
about ___________ of its weight on Earth.
SI Base Units: Mass
• The measure of the gravitational pull on
matter (gravity) is weight.
• Mass does not depend on gravity.
• As the force of Earths’ gravity on an object
increases, the object’s weight
_____________________.
• The weight of an object on the moon is
about ___________ of its weight on Earth.
SI Base Units: Mass
• The measure of the gravitational pull on
matter (gravity) is weight.
• Mass does not depend on gravity.
• As the force of Earths’ gravity on an object
increases, the object’s weight increases.
• The weight of an object on the moon is
about one-sixth (1/6) of its weight on Earth.
SI Base Units: Length
• The SI standard unit for length is the
______________.
• To express longer distances, the
__________________, ___ is used.
• To express short distances, the
_____________, _____ is used. (add to notes)
• One _____________ is 1000 meters.
SI Base Units: Length
• The SI standard unit for length is the meter.
• To express longer distances, the kilometer,
km is used.
• To express short distances, the
_____________, _____ is used. (add to notes)
• One _____________ is 1000 meters.
SI Base Units: Length
•The SI standard unit for length is the
meter.
•To express longer distances, the
kilometer, km is used.
•To express short distances, the
centimeter, cm is used. (add to notes)
•One kilometer is 1000 meters.
Derived SI Units
•Combination of SI base units form
________ ______.
•For example, area, is
________ x ________.
m
m2
m
Derived SI Units
•Combination of SI base units form derived
units.
•For example, area, is
________ x ________.
m
m2
m
Derived SI Units
•Combination of SI base units form derived
units.
•For example, area, is length x width.
m
Area = L x W
Area = m x m
Area = m2
m2
m
Derived SI Units
Quantity
Symbol
Unit name
Unit abbrev.
1.
Area
A
Square Meter
m2
2.
Volume
V
Cubic Meter
m3
3.
Density
D
4.
Molar Mass M
5. Molar Volume Vm
6.
Energy
E
Kilograms per cubic meter
Kilograms per mole
cubic meters per mole
Joule
Derivation
length x width
l x w x height
kg/ m3
kg/mol
m3/mol
J
mass/volume
m/amt. of sub.
volume/n
force x length
Derived SI Units - Volume
• The amount of space occupied by an object is
____________, and the derived SI unit is
___________ _________.
• This amount is equal to the volumne of a cube
whose edges are each ____ ___ long.
• But in a chemistry laboratory, we need a
smaller unit, so we often use
_________________ ______________, ______.
Derived SI Units - Volume
• The amount of space occupied by an object is
volume, and the derived SI unit is cubic
meters, m3.
• This amount is equal to the volume of a cube
whose edges are each ____ ___ long.
• But in a chemistry laboratory, we need a
smaller unit, so we often use
_________________ ______________, ______.
Derived SI Units - Volume
•The amount of space occupied by an
object is volume, and the derived SI unit is
cubic meters, m3.
•This amount is equal to the volume of a
cube whose edges are each 1 m long.
•But in a chemistry laboratory, we need a
smaller unit, so we often use cubic
centimeter, cm3.
Derived SI Units - Volume
(1 m3) x (100 cm/1m) x (100 cm/1 m) x (100 cm/1 m)
= 1 000 000 cm3
Derived SI Units - Volume
• When chemists measure the volumes of liquid and
gases, they often use a non-SI unit called the ________.
• **Another non-SI unit, the ________________, or ___,
is used for smaller volumes. There are _____________
mL in 1 L.
• Because there are also __________ cm3 in a liter, the 2
units, ____________ and __________
_______________ are interchangeable.
• View this in a equation: 1 L = 1 dm3 = ___________
cm3 = _________ mL
Derived SI Units - Volume
• When chemists measure the volumes of liquid and
gases, they often use a non-SI unit called the liter, L.
• **Another non-SI unit, the ________________, or ___,
is used for smaller volumes. There are _____________
mL in 1 L.
• Because there are also __________ cm3 in a liter, the 2
units, ____________ and __________
_______________ are interchangeable.
• View this in a equation: 1 L = 1 dm3 = ___________
cm3 = _________ mL
Derived SI Units - Volume
• When chemists measure the volumes of liquid and
gases, they often use a non-SI unit called the liter, L.
• **Another non-SI unit, the milliliter, or mL is used for
smaller volumes. There are 1000 mL in 1 L.
• Because there are also __________ cm3 in a liter, the 2
units, ____________ and __________
_______________ are interchangeable.
• View this in a equation: 1 L = 1 dm3 = ___________
cm3 = _________ mL
Derived SI Units - Volume
• When chemists measure the volumes of liquid and
gases, they often use a non-SI unit called the liter, L.
• **Another non-SI unit, the milliliter, or mL is used for
smaller volumes. There are 1000 mL in 1 L.
• Because there are also 1000 cm3 in a liter, the 2 units,
milliliter and cubic centimeter are interchangeable.
• View this in a equation: 1 L = 1 dm3 = ___________
cm3 = _________ mL
Derived SI Units - Volume
• When chemists measure the volumes of liquid and
gases, they often use a non-SI unit called the liter, L.
• **Another non-SI unit, the milliliter, or mL is used
for smaller volumes. There are 1000 mL in 1 L.
• Because there are also 1000 cm3 in a liter, the 2 units,
milliliter and cubic centimeter are interchangeable.
• View this in a equation: 1 L = 1 dm3 = 1000 cm3 =
1000 mL
Derived SI Units - Density
• Ever heard the riddle: Which is heavier, a pound of
feathers or a pound of lead?
• Answer: Neither is heavier, a pound is a pound no matter
what the object….but when you want to answer “lead”
you are thinking about the object’s density.
• For another example, an object made of cork feels lighter
than a lead object of the same size.
• What you are comparing in such cases is how massive
objects are compared with their size.
Derived SI Units - Density
• This property is called __________________, which is the
ratio of __________ to ______________, or ____________
divided by _______________________.
• Mathematically, the relationship for density can be written:
Density = mass/volume
or
D = MV
• By the SI base units of measurement, density is expressed as
kg/m3. Again, for a chemistry laboratory, we make the units
smaller, ___/____ or _______/ ________.
Derived SI Units - Density
• This property is called Density, which is the ratio of mass
to volume, or mass divided by volume.
• Mathematically, the relationship for density can be
written:
Density = mass/volume
or
D = M/V
• By the SI base units of measurement, density is
expressed as kg/m3. Again, for a chemistry laboratory, we
make the units smaller, ___/____ or _______/ ________.
Derived SI Units - Density
• This property is called Density, which is the ratio of mass
to volume, or mass divided by volume.
• Mathematically, the relationship for density can be
written:
Density = mass/volume
or
D = MV
• By the SI base units of measurement, density is
expressed as kg/m3. Again, for a chemistry laboratory, we
make the units smaller, g/cm3 or g/mL.
Derived SI Units - Density
• Densities of some familiar materials (Table 4):
• Solids
Density at 20oC (g/cm3)
Liquids
Density at 200C (g/mL)
• Cork
.24
Milk
1.031
• Ice
.92
Water
.998
• Sucrose (table sugar)
1.59
Sea Water
• Diamond
3.26
Gasoline
.67
• Lead
11.35
Mercury
13.6
1.025
Derived SI Units - Density
• Sample Problem A:
• A sample of aluminum metal has a mass of 8.4g. The
volume of the sample is 3.1 cm3. Calculate the density of
aluminum.
-Given: mass (m) = 8.4g & volume (v) = 3.1 cm3
- Unknown: Density (D)
Density = mass/volume = 8.4 g/3.1 cm3 = 2.7 g/cm3
Conversion Factors
• A ratio derived from the equality between two different
units that can be used to convert from one unit to the
other is a _______________________
___________________.
• For example, suppose you want to know how many
quarters there are in a certain number of dollars.
• To figure out this answer, you need to know how
_______________ and _________________ are related.
• There are ____________ quarters in __________ dollar.
Conversion Factors
• A ratio derived from the equality between two different
units that can be used to convert from one unit to the
other is a conversion factor.
• For example, suppose you want to know how many
quarters there are in a certain number of dollars.
• To figure out this answer, you need to know how
_______________ and _________________ are related.
• There are ____________ quarters in __________ dollar.
Conversion Factors
• A ratio derived from the equality between two different
units that can be used to convert from one unit to the
other is a conversion factor.
• For example, suppose you want to know how many
quarters there are in a certain number of dollars.
• To figure out this answer, you need to know how quarters
and dollars are related.
• There are 4 quarters in 1 dollar.
Conversion Factors
• There are 4 ways to express this:
1. 4 quarters/1 dollar = 1
2. 1 dollar/4 quarters = 1
3. 0.25 dollar/1 quarter = 1
4. 1 quarter/0.25 dollar = 1
• Notice that each conversion factor equals _________.
• That is because the top and bottom quantities divided in any
conversion factor and ____________ to each other. In this
case 4 quarters = 1 dollar.
Conversion Factors
• There are 4 ways to express this:
1. 4 quarters/1 dollar = 1
2. 1 dollar/4 quarters = 1
3. 0.25 dollar/1 quarter = 1
4. 1 quarter/0.25 dollar = 1
• Notice that each conversion factor equals ONE.
• That is because the top and bottom quantities divided in any
conversion factor and ____________ to each other. In this
case 4 quarters = 1 dollar.
Conversion Factors
• There are 4 ways to express this:
1. 4 quarters/1 dollar = 1
2. 1 dollar/4 quarters = 1
3. 0.25 dollar/1 quarter = 1
4. 1 quarter/0.25 dollar = 1
• Notice that each conversion factor equals ONE.
• That is because the top and bottom quantities divided in any
conversion factor and equivalent to each other. In this case
4 quarters = 1 dollar.
Conversion Factors
• You can use conversion factors to solve problems
through __________________ ____________________;
which is a mathematical technique that allows you to
use __________ to solve problems involving
________________.
• For example, to determine the number of quarters in 12
dollars, you would use a unit conversion that allows
you to change from dollars to quarters:
• Number of quarters = 12 dollars x conversion factor
Conversion Factors
• You can use conversion factors to solve problems
through dimensional analysis; which is a mathematical
technique that allows you to use units to solve
problems involving measurements.
• For example, to determine the number of quarters in 12
dollars, you would use a unit conversion that allows
you to change from dollars to quarters:
• Number of quarters = 12 dollars x conversion factor
Conversion Factors
• Then you have to decide which conversion factor gives
you an answer in the desired unit.
• In this case, you have _____________ and you want
__________________, to eliminate dollars, you must
divide the quantity by ____________________.
• That factor would be __________________ /
___________________
Conversion Factors
• Then you have to decide which conversion factor gives
you an answer in the desired unit.
• In this case, you have dollars and you want quarters, so
to eliminate dollars, you must divide the quantity by
dollars.
• That factor would be __________________ /
___________________
Conversion Factors
• Then you have to decide which conversion factor gives
you an answer in the desired unit.
• In this case, you have dollars and you want quarters, so
to eliminate dollars, you must divide the quantity by
dollars.
• That factor would be:
4 quarters/1 dollar
Conversion Factors
• And the calculation would be set
up as follows:
? quarters = 12 dollars x conversion
factor
12 dollars x 4 quarters/1 dollar = 48
quarters
• Notice that the dollars have
divided out, leaving the answer in
the desired unit, quarters.
Conversion Factors
**For review of this section, it is imperative to be
familiar with the SI Prefixes Table on page 35.**
GREEK
LATIN
10
Deka-
10 x
deci-
1/10
100
Hecto-
100 x
centi-
1/100
1000
Kilo-
100 x
milli-
1/1000
Million
Mega-
Million x
micro-
millionth
Billion
Giga-
Billion x
nano-
billionth
Deriving Conversion Factors
• You can derive conversion factors if you know the
relationship between the unit you HAVE and the unit you
WANT.
• For example, from the fact that deci- means “1/10”, you
know that there is a 1/10 of a meter per decimeter and that
each meter must have 10 decimeters. (1m = 10dm).
• You can write the following conversion factor relating
meters and decimeters:
(1 meter/10 decimeter) and (.1 meter/1 decimeter) and
(10 decimeter/1 meter)
Deriving Conversion Factors
• Sample Problem B: Express a mass of 5.712 grams in milligrams and in
kilograms.
• Given: 5.712 grams
• Unknown: mass in mg and kg
• 1 g = 1000 mg
• Possible conversion factors:
• 1000 mg/1 g and 1 g/1000 mg
• To derive an answer in mg, you’ll need to multiply 5.712 g by
1000mg/g:
• 5.712 g × 1000 mg/1 g =5712 mg
• Answer in kg:
• 5.712 g × 1 kg/1000 g= .005712 kg