Topic 1
Matter and Measurements
AP Chemistry
How to be Successful in
AP Chemistry
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Memorize strategies not equations!
Study a lot!
Work ALL the problems.
Self-evaluate after test results.
Make use of Tutorial.
Start a Study Group
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Chapter 1: Matter and Measurement
Overview:
 The Study of Chemistry
 Classifications of Matter
 Properties of Matter
 Units of Measurement
 Uncertainty in Measurement
 Dimensional Analysis
 Basic Math Concepts
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Chemistry
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The study of matter and the changes it
undergoes
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Matter
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Anything that has mass and occupies
space
Characterized by physical and chemical
properties
Law of the Conservation of Mass - matter
is neither created nor destroyed in
chemical reactions
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Element
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An element is a pure substance composed of
one type of atom.
An atom is the smallest particle of an element
that retains the chemical properties of the
element.
An element is the most basic form of matter
under ordinary circumstances
Simplest chemical substance
Only a few elements are found in their free state
(nitrogen, oxygen, gold, etc.)
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Elements and the Periodic Table
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Each element is represented by a name and
a symbol. (Periods/groups - alkali metals,
alkaline earth metals, halogens, noble gases)
The first letter is always capitalized the
second (and third) are never capitalized.
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Compound
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A unique substance composed of two or more
elements that are chemically combined (i.e.
joined intimately, not just mixed together)
Pure compounds have definite compositions and
properties
Require complex chemical procedures to
separate into simpler substances (elements)
Compounds include water, table salt, sugar, etc
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Properties of Substances
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Elements and Compounds are pure substances.
Properties describe the particular characteristics of a
substance
Pure substances have definite composition and
definite, unchanging properties
Physical properties - can be observed without
changing the substance
Chemical properties - require that the substance
change into another
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Physical States
The three physical states are solid, liquid
and gas
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solids - have a definite shape and volume
liquid - have a definite volume but not a
definite shape
gas - neither a definite volume or shape
A substance exists in a particular physical
state under defined conditions
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Phase Changes
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Melting point or freezing point
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temperature at which a substance changes from solid to liquid
Boiling point or condensation point
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temperature at which a substance changes from liquid to gas
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Density
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ratio of the mass of a substance to the volume of
that mass
usually measure in g/mL for solids and liquids; g/L
for gases
also a conversion factor relating the mass of a
substance to it’s volume
Specific gravity is the ratio of the mass of a
substance to the mass of an equal volume of water
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What’s happening?
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Density Calculation
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Equation
d=m/V
Example:
If an object has a mass of 15.0 g and a
volume of 10cm3 what’s the objects
density?
d = 15.0 g/ 10.0 cm3 = 1.50 g/cm3
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Temperature and its Measurement
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Temperature - measure of the intensity of the
heat of a substance
Thermometer - device to measure
temperature
Kelvin - K - SI unit of temperature
Celsius - °C - commonly used unit
Fahrenheit - °F - only used in USA
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The Kelvin scale
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The idea of negative temperatures is a
problem for any mathematical treatment of
temperature dependent properties.
It was found that a practical minimum
temperature did exist (absolute zero) which
has a value of
-273.15°C
This is defined as 0 K (no degree sign)
The Kelvin degree is the same size as the
Celsius degree (K = °C + 273.15)
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Temperature Scale Comparison
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Chemical Properties
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Chemical properties - involve how a
substance changes into another
Sometimes quite difficult to determine
Some examples are burning (as opposed to
boiling) and color changes
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A mixture is a combination of two or more substances
in which the substances retain their distinct identities.
1. Homogenous mixture – composition of the
mixture is the same throughout.
2. Heterogeneous mixture – composition is not
uniform throughout.
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Mixtures
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Combinations of two or more substances
Can be separated by exploiting different physical
properties (filtration, distillation, crystallization,
chromatography)
Have chemical and physical properties that are
different from the substances that make them up
The percentages by mass of the components of
a mixture can be varied continuously
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Heterogeneous Vs. Homogeneous
Mixtures
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Physical means can be
used to separate a
mixture into its pure
components.
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Physical means can be used to separate a mixture
into its pure components. (Mechanical process)
magnet
distillation
filtration
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Physical Change: the composition of the
substance remains the same but the state
changes.
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Chemical Change: a new substance is
formed.
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Physical Properties: Identifying properties
of a substance.
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Density
Solubility
Color
Melting/Boiling Point
Crystalline Shape
Malleability, Ductility, Conductivity, Luster
Etc.
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Extensive and Intensive Properties
An extensive property of a material depends upon
how much matter is is being considered.
• mass
• length
• volume
An intensive property of a material does not
depend upon how much matter is is being
considered.
• density
• malleability
• color
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1.6
Solutions
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A type of homogeneous mixture
Usually involves a liquid phase, but can be
solid-solid, liquid-liquid, solid-liquid, etc.
The pure substances can be in different
phases but form a homogeneous mixture
(table salt and water, for example)
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Measurements and Units
Measurement - determines the quantity,
dimensions or extent of something
1.Consist of two parts
a. a numerical quantity (1.23)
b. a specific unit (meters)
Unit - a definite quantity adapted to as a
standard of measurement
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Features of Measured Quantities
When we measure a number, there are physical
constraints to the measurement
Instruments and scientists are not perfect, so the
measurement is not perfect (i. e., it has error)
The error in the measurement is related to the
accuracy and the precision of the measurement
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Accuracy and Precision
Accuracy – how close the measurement is to
the “true” value (of course we have to know
what the “true” value is)
Precision – is a measure of how closely
individual measurements agree with one
another.
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Example: Accuracy and Precision
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Equations for Precision and Accuracy
1. Precision
2. Accuracy
Absolute Error
% AE = (True value-Avg Value) X 100
True Value
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Significant Figures
•Any digit that is not zero is significant
1.234 kg
4 significant figures
•Zeros between nonzero digits are significant
6006 m
AP Chemistry
Exam Hint:
You must be within
1 sig fig – it does
not need to be
perfect, but sig
figs DO count!
4 significant figures
•Zeros to the left of the first nonzero digit are not significant
0.08 L
1 significant figure
•One or more final zeros to the right of the decimal point are
significant
2.00 mg
3 significant figures
0.00420 g
3 significant figures
10.006000
8 sig figs
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Counting Significant Figures
Atlantic / Pacific Method
a. Absent Decimal- Start on “atlantic” side of
number & cross out all zeroes until 1st nonzero
digit is reached, remaining digits are significant
b. Present decimal- start on the “pacific” side of
the number & cross out all zeros until the 1st
nonzero digit Is reached, remaining digits are
significant
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2. Examples:
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How many significant figures are in
each of the following measurements?
24 mL
2 significant figures
3001 g
4 significant figures
0.0320 m3
3 significant figures
6.400 x 104 molecules
4 significant figures
560 kg
2 significant figures
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Significant Figures
Addition or Subtraction
The answer cannot be more accurate than any of the
original numbers.
89.332
+1.1
90.432
one significant figure after decimal point
round off to 90.4
3.70
-2.9133
0.7867
two significant figures after decimal point
370
-291.33
78.67
Number is rounded to “tens” place
round off to 0.79
round
off to 80
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Significant Figures
Multiplication or Division
The number of significant figures in the result is set by the original
number that has the smallest number of significant figures
4.51 x 3.6666 = 16.536366 = 16.5
3 sig figs
round to
3 sig figs
6.8 ÷ 112.04 = 0.0606926 = 0.061
2 sig figs
round to
2 sig figs
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Significant Figures
Exact Numbers
Numbers from definitions or numbers of objects are considered
to have an infinite number of significant figures
The average of three measured lengths; 6.64, 6.68 and 6.70?
6.64 + 6.68 + 6.70
= 6.67333 = 6.67 = 7
3
Because 3 is an exact number
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Scientific notation format
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Scientific notation and significant
figures
1. When using scientific notation the base
must be written with the correct number of
significant digits
2. All zeroes are significant when using
scientific notation
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Measurement of mass, length and
volume
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In the United States, we use a fairly awkward
system of measurement for most things - the
English system Scientists use the metric and SI
systems of units for the measurement of physical
quantities
This system using standard units based on very
precisely known properties of matter and light
Prefixes are used in from of the units to indicate
powers of ten
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SI Units
Measurement
Unit
Symbol
Mass
Kilogram
kg
Length
Meter
M
Time
Second
s
Temperature
Kelvin
K
Quantity
Mole
mol
Energy
Joule
J
Pressure
Pascal
Pa
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SI Prefixes
Prefix
Symbol Power
Prefix
Symbol Power
tera-
T
1012
deci-
d
10-1
giga-
G
109
centi-
c
10-2
mega-
M
106
milli-
m
10-3
kilo-
k
103
micro-
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10-6
hecto-
h
102
nano-
n
10-9
deca-
da
101
pico-
p
10-12
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. Base Units
Mass - the quantity of matter that a sample contains
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Note that weight is a measure of the attraction of
gravity for a sample and it varies depending on the
distance of the mass to a planet or moon
Scientists often speak imprecisely of the “weight” of
an amount of substance. They really mean mass.
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Basic SI units/Derived units
Used to generate new Units
 Volume - space a given quantity of matter
occupies
 Volume - expressed in terms of length - m3
 m3 - an inconveniently large volume, so we
use liter (L; one cubic decimeter)
 We often use a mL (1 cubic centimeter) for
more manageable amounts of matter
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Converting between units
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The standard method to convert between two
different units is the factor-label or
dimensional analysis method
Dimensional analysis converts a
measurement in one unit to another by the
use of a conversion factor
Conversion factors are developed from
relationships between units
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The speed of sound in air is about 343 m/s. What is
this speed in miles per hour?
meters to miles
seconds to hours
1 mi = 1609 m
1 min = 60 s
1 mi
60 s
m
x
x
343
s 1609 m
1 min
1 hour = 60 min
60 min
mi
x
= 767
hour
1 hour
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