Classifying Matter
Let’s start small and work up from
there.
• Atom – the smallest unit of an element
that maintains the properties of the
element
• The can be physically mixed or chemically
joined to make up other forms of matter
Pure Substance
• A sample of matter, either a single
element or a single compound, that has
definite chemical and physical properties
Figure 14,
Page 22
Physical Properties
• Characteristic of a substance that does
not involve a chemical change
• Examples: Density, color, hardness
• Does this test change the chemical
make-up of the material?
• No
Chemical Property
• Characteristic of matter that describes a
substance’s ability to participate in
chemical reactions
• Example: Oxidation, flammability, and
combustion
• Does this test change the chemical
make-up of the material?
• Yes
Figure 12, page 19
Elements
• A pure substance that contains only one
kind of atom
• It cannot be separated or broken down
into simpler substances by chemical
means.
• All atoms of the same element have the
same atomic number
• Elements may bond in different ratios with
itself. These are called allotropes.
Compounds
• A pure substance that is made up of two
or more different elements joined by
chemical bonds.
• They are represented by formulas
Molecules
• The smallest unit of a substance that keeps
all of the physical and chemical properties
of that substance.
• It can consist of one atom or two or more
atoms bonded together
• In other words, molecules can be of the
same element or of the same compound
only
All of the following are molecules,
but are they compounds or
elements?
Element
• Br2
Compound
• H2O
Element
• O2
Element
• O3
Compound
• C12H22O12
Mixtures
• A combination of two or more substances
that are not chemically combined.
• Examples are air, ice tea, and even cake
batter
• The proportions of the substances can
vary
Mixtures can be homogeneous or
heterogeneous
• Homogeneous mixtures have a uniform
structure or composition throughout
• Because of the even distribution, any two
samples taken from the same homogenous
mixture will have the same proportions of
ingredients
• Examples: Gasoline, air, and syrup
Mixtures can be homogeneous or
heterogeneous
• Heterogeneous mixtures are not evenly
mixed.
• Different regions of the same
heterogeneous mixture will have different
proportions
• Examples: Pulpy Orange Juice, chocolate
chip cookie dough, and granite.
Visuals of Homogeneous and
Heterogeneous Mixtures
Figure 19, Page 26
Mixtures verses Compounds, How
can you tell which is which?
• Compounds are two or more elements
that are chemically bonded together.
• Mixtures are two or more substances
physically mixed together, but not
chemically joined
Therefore
• Properties of a mixture reflect the
properties of the substances mixed in it;
compounds have new properties of
their own.
• Compounds have definite composition;
mixtures composition can vary from
mixture to mixture of the same
substances
In other words,
• You can have a mixture of hydrogen gas
and oxygen gas in various concentrations,
but the compound water, H2O, will always
have 2 hydrogen atoms bonded to one
oxygen atom.
Figure 20, Page 28
Classify each of the following as an
element, compound, homogeneous
mixture, or a heterogeneous mixture
• Iron (III) Oxide (Fe2O3)
• 24 Karat gold
• Sugar Water
• Ozone
• Fizzy Soda
• Flat Soda
Compound
Element
Homogeneous Mix
Element
Heterogeneous Mix
Homogeneous Mix
Separating Mixtures
Since mixtures are just physically
combined, they can be separated.
Separating Mixtures
• Some Methods include:
– Filtering – separation of a mixture’s components through
differences in particle size
– Decanting – a fancy term for separating two components
by pouring
– Distillation – used to separate two liquids based on their
differences in boiling points
– Magnetism – used to separate magnetic substances
– Evaporation – removing a liquid to leave a solid behind
– Centrifuge – separates substances of different densities
using a fast rotational motion
– Chromatography – Separates two substances by using a
mobile phase and a stationary phase