The Basics of
AP CHEMISTRY
This is a PowerPoint that is
designed for people who have
skipped a year in between
Chemistry and AP Chemistry
and do not remember a single
thing that they learned.
OVERVIEW
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The History of
Chemistry
The Scientific Method
Laws and Theories
Units of Measurement
Weight/Mass
Correct way to Measure
Significant Figures
Rounding
Precision/Accuracy
Density
Matter
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Mixtures
Physical/Chemical
Changes
Compound/Element
Important Laws
Dalton’s Atomic Theory
Atomic Weight/Mass
Electrons
Radioactivity
Atoms
Protons/Neutrons
Isotopes
Bonding
The Periodic Table
Acids/Bases
What is Chemistry?
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According to the internet
(dictionary.com), chemistry is the
science of the composition, structure,
properties, and reactions of matter,
especially of atomic and molecular
systems.
Historic Chemistry
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The Greeks were the first to use
Chemistry to try to explain why
chemical changes occur.
– Demokitos, Leucippos
Historic Chemistry
Continued
There was also a time period where
alchemy took over chemistry (this was
about 2000 years).
 They discovered several elements and
were able to prepare mineral acids.
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Historic Chemistry
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Continued
Modern Chemistry ~ 16th century
– Bauer ~ systematic metallurgy
– Paracelsus ~ medicinal chemistry
Historic Chemistry
Continued
The first real chemist to actually
perform experiments that gave him
quantitative results was Boyle.
 We all know him for the law that he
founded…Boyle’s Law.

– This law states the relationship between
pressure and the volume of air.
Historic Chemistry
Continued
Oxygen was first observed by
Scheele/Priestley.
 Stahl studied combustion and learned of
all its properties and exactly how it
works.
 Oxygen was originally called
dephlogisticated air
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The Scientific Method
This method was developed in order for
scientists to have guidelines for solving
problems.
 The steps of the scientific method
include making observations,
formulating a hypothesis, and
performing experiments to get results
and make conclusions.
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A theory…
A theory is also known as a model.
 A theory is specifically a hypothesis that
has been tested to such an extent that
the explanation for the outcome of the
experiment remains constant.
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A Natural Law
This is a summary of the observed
behavior that has been taking place.
 A law summarizes what has happened
and what should happen if a similar
experiment were to be performed.
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Units of Measurement
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There are 7 basic SI (International
System) units that are needed:
– Mass - kilogram (kg)
– Length - meter (m)
– Time - second (s)
– Temperature - kelvin (K)
– Electric Current - ampere (A)
– Amount of Substance - mole (mol)
– Luminous Intensity - candela (cd)
Units of Measurement
P R E F IX
E xa
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There are
also prefixes
that are used
in the SI
system.
P eta
T era
G ig a
M eg a
K ilo
H ecto
D eka
D eci
C en ti
M illi
M icro
N an o
P ico
Fem to
A tto
Continued
E X P O N T E N T IA L
N O T AT IO N
18
10
15
10
12
10
9
10
6
10
3
10
2
10
1
10
0
10
-1
10
-2
10
-3
10
-6
10
-9
10
-1 2
10
-1 5
10
-1 8
10
IMPORTANT INFORMATION
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Something that is important to
remember when taking AP Chemistry:
– 1 liter = (1 dm)3 = (10 cm)3 = 1000 cm3
– 1 liter = 1000 cm3 = 1000 mL
Weight vs. Mass
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Mass is a measure of the resistance of
an object to change in its state of
motion.
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Weight is the response of mass to
gravity.
Weight vs. Mass
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YOU CANNOT USE MASS AND WEIGHT
INTERCHANGABLY.
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We are correctly supposed to use the
term weight because we are comparing
the object’s mass to the standard mass,
however, mass is used consistently in all
types of scientific equations.
The CORRECT Way to Measure
When measuring a volume or the length
of an object, it is necessary to record all
of the numbers that are known and then
estimate the last place value when not
using a measuring device that measures
the object’s exactly.
 This should be done consistently,
accurately, and precisely.
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Significant Figures
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Significant figures are always used in
scientific calculations.
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They can be very confusing, but once
they are understood, they are a piece of
cake.
Significant Figures
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Continued
When recording data, all the known
values are recorded and the last digit is
an estimated value.
Significant Figure Rules
Nonzero integers always count as
significant figures.
 Leading zeros do not count. They just
show the position of the decimal point.
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– Example: 0.00065
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There are only two significant figures in this
number. The zeros that precede the 65 do not
count.
Significant Figure Rules
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Any zero that is in between two
nonzero numbers always counts
– Example: 6.00045
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There are six significant figures in this number.
Zeros like these always count as significant
figures.
Zeros that are found at the end of
numbers never count.
– Example: 4.7800
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There are only three significant figures in this
number. The two zeros at the end do not
count.
Significant Figure Rules
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A final rule to abide by is the exact
number rule. Exact numbers cannot be
changed and are assumed to have an
infinite number of significant figures.
– Example: We performed 5 experiments
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The five experiments cannot be changed in any
way.
– Example: 1 liter = 1000 mL
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This is also an exact number and cannot be
changed.
Mathematical Operations
Involving Significant Figures
When multiplying or dividing numbers,
the number of significant figures needs
to be taken into account.
 The answer needs to have the same
amount of significant figures as the
number with the least amount of
figures.
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– Example: 5.677 * 3.4 = 19
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3.4 only has two significant figures and
therefore the answer can only have two
significant figures
Mathematical Operations
Involving Significant Figures
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When adding and subtracting numbers
you would go by the number of decimal
places that the number has. The
number with the least amount is the
one that you use as your reference in
the answer.
– Example: 4.0089 + 2.4 = 6.4
Rounding Rules
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In case you forgot how to round
properly, you can simply follow these
directions
– ALWAYS carry digits through until the final
answer. Then you can round.
– When rounding numbers, if a number after
the number that you are stopping at is at 5
or above, round up. If it is less, then keep
the number as it is.
Review of Previous Slides
Now, if you wanted to round this
number to three significant
figures…what would it look like?
4.06789
 The number would be 4.07 rounded to
three significant figures.
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Precision vs. Accuracy
Precision is the degree of agreement of
several measurements to original
value.
 Accuracy is the degree of agreement of
a single measurement in comparison to
the original value.
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DENSITY
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Density is the mass of a substance per
unit Volume of the substance.
– Formula for density is as follows:
Density = mass/volume
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Any density can be determined when
these two items are known.
What is Matter?
Anything occupying space and having
mass.
 The four different states of matter
include:
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solid
liquid
gas
plasma
Mixtures
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Mixtures are pure substances that are
composed of more than one thing.
– Homogenous mixture (solutions) indistinguishable parts
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Example: air
– Heterogeneous mixture - distinguishable
parts
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Example: Sand in Water
Mixtures
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Pure Substances
– These are substances that have a constant
composition
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An example of this would be water
Physical Changes
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This is a change that is characterized by
the fact that the substance does not
change in composition, rather it just
changes in shape and form
– An example of a physical change is a
substance that changes from boiling to
freezing. It has not changed in
composition, just the way that it looks.
Chemical Changes
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Chemical changes are characterized by
the fact that the substance would
change in composition and technically
become something else.
– An example of a chemical change would be
a metal that has rusted. The chemical
composition of the metal would no longer
be the same.
Separating Mixtures
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There are many different ways to separate
mixtures.
– Distillation (mixtures are heated and the
components of the mixture separate)
– Filtration (the liquid passes through a filter and
separates)
– Chromatography (components have different
affinities for the two phases (stationary and
mobile) causing them to move at different speeds
Compound vs. Element
A compound is a substance with
constant composition that can be
broken down into elements by the use
of chemical processes.
 An element is a substance that cannot
be broken down any further by any type
of chemical or physical means.
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A VERY Important Law
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The Law of the Conservation of Mass
– This law states that mass is never created
nor destroyed, it is conserved through
chemical and physical changes of any kind.
This is the basis of
all of chemistry!
Another VERY Important Law
 Proust’s
Law, or the Law of
Definite Proportions states that
a compound always has a constant
composition. It contains exactly
the same proportion of elements by
mass, as Proust put it.
Yet Another VERY Important Law
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THE LAW OF MULTIPLE PROPORITONS:
– States that when two elements form a
series of compounds, the ratios of the
masses of the second element that
combine with 1 gram of the first element
can always be reduced to small whole
numbers.
Dalton’s Atomic Theory
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There are four parts to Dalton’s Theory:
– Every element is made up of tiny particles called
atoms.
– All atoms of a single element are identical. The
atoms of different elements are different in one
way or another.
– To form a chemical compound, atoms of unalike
elements need to be combined.
– Chemical reactions result in the moving around of
atoms (changes in the way that the atoms bond).
Atomic Mass/Weight
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Dalton was the first to come up with a
table that showed the atomic masses of
elements that were known. This was
later proved to be incorrect.
Atomic Mass/Weight
Continued
Gay-Lussac and Avogadro were the first
to use special formulas that are now
used in order to find the formulas for
compounds.
 Avogadro took this further and made a
hypothesis that says:
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– At the same temperature and pressure,
equal volumes of different gases contain
the same number of particles.
J.J. Thomson and the Electron
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J.J. Thomson used cathode ray tubes and
found that the ray in middle of the tube was
really a stream of negatively charged particles
that are now called electrons.
He also determined the charge to mass ration
of the electron:
– e/m = -1.76 x 108 C/g
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He also assumed that all atoms must have
electrons, however, atoms are overall
neutrally charged, therefore he assumed that
there must be positive charge somewhere!
Plum Pudding?
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Plum pudding is referred to as the
diagram of the proton because there is
a cloud and there are raisin like circles
floating through it, just like in plum
pudding. This was thought to be the
original model of the proton.
Robert Millikan
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He, with the help of Thomson, was able
to calculate the mass of the electron:
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9.11 X 10-31 kilogram
THAT IS A VERY
SMALL NUMBER!!!!
Radioactivity
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Becquerel was the first to discover
radioactivity.
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Radioactivity is the spontaneous
emission of either a gamma, beta, or
alpha particles caused this.
Nuclear Atom
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This is an atom with a dense center of
positive charge with the electrons
moving around the nucleus at a
distance that is large relative to he
nuclear radius.
Protons and Neutrons
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The nucleus contains both protons and
neutrons.
– Protons are positively charged atomic
partices.
– Neutrons are atomic particles that have no
charge at all.
What is an Isotope?
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These are a form of the atom that
contains the same number of protons,
but a completely different number of
neutrons.
When Elements Come Together
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There are chemical bonds that hold atoms
together.
The atoms can form bonds by sharing
electrons (covalent bond) and those atoms
together are called molecules.
A way to represent the coming together of
atoms is by a chemical formula, like NaCl.
This is the coming together of Sodium and
Chlorine. The Na and the Cl are the
abbreviations for those specific elements.
More Bonding
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Ionic Bonding is when there is a force
of attraction between oppositely charge
ions.
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Ionic bonding terms:
– A solid that has an ionic bond ~ ionic solid
or a salt.
THE PERIODIC TABLE
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A chart that shows
all the elements, as
well as the groups/
families and periods,
and their descriptions
is known as a periodic
table.
The Periodic Table
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Continued
There are metals and nonmetals.
– Metals can conduct electricity and heat. The
also usually have lustrous appearance.
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Example: Copper
– Nonmetals usually appear in the upper-right
corner of the table. The lack physical
properties like the metals. The usually gain
electrons in reactions with metals. They like
covalent bonding.
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Example: Chlorine
Sections of the Periodic Table
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All elements that are in the same
vertical column (group/family) have
similar characteristics (chemically).
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Alkali Metals – Group 1A
– Active elements, have a +1 charge when
reacting with nonmetals
Sections of the Periodic Table
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Alkaline Earth Metals – Group 2A
– Form ions with a +2 charge when reacting with
nonmetals.
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Halogens – Group 7A
– All form diatomic molecules
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Group 8A (Noble Gases) can exist under
normal conditions as monatomic gases and
they have little chemical reactivity.
Sections of the Periodic Table
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The horizontal rows of the periodic
table are known as periods
ACIDS
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When dissolving a substance in water,
certain molecules produce a solution
containing free hydrogen ions. These
substances are called acids. They do
no contain oxygen and have a greater
amount of hydrogen ions in comparison
to hydroxide ions.
BASES
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The exact opposite is true for bases.
These substances, when dissolved in
water, tend to have a lot more of
hydroxide ions, rather than having
hydrogen ions.
I hope that this presentation helped
all of those that are now taking AP
Chemistry and really do not
understand anything that they
learned in regular or Advanced
Chemistry. I know that if I would
have had something like this, it
would have helped a lot in
preparation for the first day of
class…Good Luck!
THE END