Transcript File

CHEMISTRY
Composition of Matter

Matter - Everything in
universe is composed of
matter
 Matter is anything that
occupies space or has
mass
 Mass – quantity of
matter an object has
 Weight – pull of
gravity on an object
Elements
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Pure substances that cannot be broken
down chemically into simpler kinds of
matter
More than 100 elements (92 naturally
occurring)

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90% of the mass of a
living thing is composed of
4 elements (oxygen,
carbon, hydrogen and
nitrogen)
Each element is
represented by a
chemical symbol
 Consists of 1-2 letters
 First letter is always
capitalized
Atoms

The smallest particle of
an element
Nucleus
Neutrons 0
Protons +
Electrons -
The Nucleus
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2 main regions:
Nucleus & electron
shell
Nucleus consists of
positive charged
protons and neutral
neutrons
Nucleus contains most
of the mass of the
atom
The Protons

All atoms of the same element have the
same number of protons
Atomic number
Atomic symbol
Element name
Atomic mass
The Neutrons
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The number varies slightly among atoms
of the same element
Atoms of the same element with
different number of neutrons are called
Isotopes
Atomic Mass

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The number of protons PLUS
neutrons in an atom determines its
atomic mass number.
The number of electrons is equal to
the number of protons in an atom.
The Electrons

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Negatively charged high energy particles
with little or no mass
Travel at very high speeds at various
distances (energy levels) outside of the
nucleus
Periodic Table

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Elements are arranged by their
atomic number on the Periodic Table
The horizontal rows are called
Periods & tell the number of
energy levels
Vertical groups are called Families &
tell the outermost number of
electrons
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A compound is a pure
substance made up of
atoms of two or more
elements
Chemical formula is used
to represent a
compound.
Examples:

H20, CH4, CO2
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Molecules are the
smallest part of
a compound.
Some molecules
are large and
complex
Chemical Formulas

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Subscript after a symbol tell the
number of atoms of each element
H20 has 2 atoms of hydrogen & 1
atom of oxygen
Coefficients before a formula tell
the number of molecules
3O2 represents 3 molecules of oxygen
or (3x2) or 6 atoms of oxygen

The properties
of a compound
are different
from
properties of
its elements.

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The outermost
electrons in elements
determine if they will
combine/bond with
others.
Elements react/bond
with other elements to
fill their outer energy
level – becoming more
stable.
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Most atoms are not stable
in their natural state
Tend to react (combine)
with other atoms in order
to become more stable
(undergo chemical
reactions)
In chemical reactions
bonds are broken; atoms
rearranged and new
chemical bonds are
formed that store energy.
Covalent Bonds

Formed when two atoms share one or
more pairs of electrons
Ionic Bonds
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Some atoms become stable by losing or
gaining electrons. These atoms are
called Ions.
Atoms that lose electrons are called
positive ions.
Atoms that gain electrons are called
negative ions.

Because positive and negative electrical
charges attract each other ionic bonds
form = attraction between a positive ion
and negative ion.
States of Matter
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Atoms are in constant motion
The rate at which atoms or molecules in
a substance move determines its state.
Solutions
Solutions

A solution is a
mixture in
which 2 or
more
substances are
uniformly
distributed in
another
substance
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Solute is the
substance
dissolved in the
solution
 Particles may
be ions, atoms,
or molecules
Solvent is the
substance in which
the solute is
dissolved
Water is the
universal solvent
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Solutions can be composed
of varying proportions of a
given solute in a given
solvent --- vary in
concentration (measurement
of the amount of solute)
A saturated solution is one
in which no more solute can
be dissolved.
Aqueous solution (water as
solvent) are universally
important to living things

Dissociation of water
 Breaking apart of the water molecule
into two ions of opposite charge

H2O  H+ + OH-
OH- is the hydroxide ion
H+ is the hydrogen ion
Acids and Bases
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One of the most important aspects of a
living system is the degree of acidity or
basicity
Acids produce H+ ions
Bases produce OH- ions
pH Scale
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pH scale
measures the
concentration
of H+ ions and
goes from 1
to 14
1-7 are acids
7 is neutral
8-14 are
bases
 Each pH is 10X
stronger than next
 e.g. ph 1 is 10 times
stronger than ph 2
Buffers
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Control of pH is very
important
Most enzymes function
only within a very
narrow pH
Control is accomplished
with buffers made by
the body
Buffers keep a neutral
pH (pH 7)

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Buffers neutralize
small amounts of
either an acid or
base added to a
solution
Complex buffering
systems maintain
the pH values of
your body’s many
fluids at normal and
safe levels