Elements
Pure
Substances
Compounds
Matter
Homogeneous
Mixtures
ANYTHING WITH MASS AND VOLUME
Heterogeneous
Mixtures and Pure
Substances
Elements
• Matter that consists of two or more
substances mixed together but not
chemically combined is called a mixture.
• Elements are the simplest pure
substance.
– Examples: hydrogen, carbon, and
oxygen.
• A pure substance is made of only one
kind of material and has definite
properties.
Compounds
• A molecule is formed when two or more
atoms combine.
• Compounds are pure substances that are
made of more than one element bound
together.
– Examples: water, table salt, and carbon
dioxide.
• The smallest particle of an element
that has the properties of that
element is called an atom.
MIXTURES
Heterogeneous vs. Homogeneous
• Homogeneous matter: matter that has
identical properties throughout.
– Examples: Sugar, salt, water, and whipped
cream
• Heterogeneous matter: matter that has
parts with different properties.
– Examples: granite, soil, potpourri
1
Conservation
• Law of Conservation of Matter
(Mass): matter cannot be created or
destroyed.
• Law of Conservation of Energy:
Energy cannot be created or
destroyed; it may only change from
one form to another.
Virtually everything that is, is made up
of atoms.
To the very small...
Matter and energy MUST be
conserved; it’s the LAW!
From the very large...
We are all made of atoms…and only atoms.
This includes
you and me!
2
Currently we
have about 115
kinds of atoms. In
the natural world
there exists 88
different kinds of
atoms.
The others have
been artificially
produced in
laboratories.
Making stuff nature
never dreamed of.
We call each kind of atom an element,
and give it a specific name and symbol.
Copper
Gold
Cu
Au
The Elements Song
Periodic Table
Abundance of
the elements, by
weight
The Earth’s interior is
rich in iron
Sand is made of
Silicon & Oxygen
3
Atoms are made up of protons,
Of course real atoms
neutrons, and electrons.
The ocean
waters are made
of oxygen &
hydrogen
don’t look anything
like this!
Protons and neutrons are found in
the nucleus of atoms -- roughly
at the center
Electrons
travel around
the nucleus.
Different kinds of atoms, or elements, are
different because they have different numbers of
protons.
They don’t look
anything like
this either!
We list the elements by
their atomic numbers the number of protons
they have.
Hydrogen, number 1
Physical Properties
Helium, number 2
Physical Changes
• Physical properties: characteristics that
can be observed without changing the
identity of the substance.
• Physical change: a change in the physical
form or properties of a substance that
occurs without a change in composition.
• Examples:
• Examples:
–
–
–
–
–
–
mass
volume
color
shape
texture
density
–
–
–
–
melting
freezing
grinding
dissolving
4
Chemical Properties
• Chemical property: describes a
substance’s ability to change into a
different substance.
• Examples:
– flammability
– reactivity
Indications of a Chemical Change…
Flames
Chemical Changes
• Chemical change: occurs when a
substance changes composition by
forming one or more new
substances. (bonds are broken
and bonds are formed)
• Example:
– HCl + NaOH → NaCl + H2O
Evaporation is a
physical change
Gas is given off (not to be confused with
boiling)
Color Change
Breaking is a physical
change.
Boiling is a change of
state, and therefore a
physical change!
5
Burning is a Chemical Change
Rusting is a
Chemical Change
6