Classification of Matter III
Do Now
that has a uniform
composition throughout is known as
a __________.
 A physical property is a
characteristic that can be observed
without performing a _____ _____.
 A homogeneous mixture is also
known as a __________.
 Matter
Chemical Changes
 The general form of any chemical
reaction is:
 reactants
→ products
reactants are the starting
materials
 The products are the substances
formed as a result of the rxn
 The
Chemical Properties
chemical property is a
characteristic that can be observed
or measured only by performing
a chemical reaction
A
to undergo combustion
 Ability to rust
 Reacts with hydrogen
 Ability
Chemical Changes
any chemical reaction, the
chemical properties of the
substances present WILL change
 This is due to the fact that the
reactants are changing into
products
 During
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Chemical Changes
 When iron is placed in contact
with oxygen gas at room
temperature, a chemical reaction
occurs – the iron rusts
 The fact that iron undergoes a
reaction in the presence of oxygen
is an example of a chemical
property of iron
Chemical Changes
 Reversible
 Charging/discharging
a rechargeable
battery
 Irreversible
 Discharging
a non-rechargeable battery
 Cooking an egg
 Burning a log in your fireplace
 rusting
Chemical Changes
 Fe
+ O2 → Fe2O3
 reactant1
changes can be reversible
or irreversible
irreversible/unidirectional
reversible
 Chemical
Recognizing Chemical Changes
 Possible clues include:
transfer of energy
 A change in color
 The production of a gas
 The formation of a precipitate
A
of these signs prove that a
reaction occurred!
 NONE
Recognizing Chemical Changes
only way to prove that a
chemical change has occurred is
to test the chemical composition
of the substances present, both
before and after the reaction
 The
 H2O(l)
→ H2(g) + O2(g)
+ reactant2 → product1
Physical Properties
physical property is a
characteristic that can be observed or
measured without performing a
chemical reaction
A
 Density
 Color
 Hardness
 Electrical
 Boiling
conductivity
point/melting point
 Phase
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Physical Changes
 Example:
phase changes
 Melting
 Boiling
 Physical
changes can be reversible or
irreversible
 Reversible
 Phase
a physical change some
physical property of a material
changes, but the chemical
composition remains the same
 During
Physical methods of separation
 Filtration
 Physical
changes are always reversible
 Irreversible
 Cracking
an egg
 Ripping a piece of paper
 Cutting your hair
Physical methods of separation
 Chromatography
size
 Distillation
 Boiling
Physical Changes
point
 Speed
of movement due to physical
size and/or electric charge
 Crystallization
 Different
solubilities of the
components of a mixture
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