CHAPTER 2
How to classify?
Devise a classification system for the following
list of things:
Orange Lime
Plum
Apple
Pear
Rose
Violet
Daisy
Gold
Silver
Explain what criteria you used to place each
item.
CLASSIFYING MATTER
MATTER
PURE
SUBSTANCE
ELEMENT
COMPOUND
MIXTURE
HOMOGENEOUS
HETEROGENEOUS
definitions
• Pure Substance:
– MATTER THAT ALWAYS HAS THE SAME
COMPOSITION
• Mixture:
– A PHYSICAL COMBINATION OF 2 OR MORE
SUBSTANCES
more definitions
Two categories of Pure Substances:
Element
– Can’t be broken down into simpler
substances
– Organized on Periodic Table
– Each contain different types of atom
– Amazing: Only about 110 different atoms
make
Elements some more
Element
• 1 or 2 letters (if 2, only first letter is
capitalized)
• Why?
– Easier – shorter for lazy scientists
– Helps scientists of all nationalities communicate
AZOTE STICKSTOFF
Both have symbol N
Compound
• Can be broken down only by chemical reaction
• Examples:
H2O SiO2 C6H12O6
• Proportions are FIXED
– All water everywhere forever has 2 H and 1 O
• Properties of Compound are DIFFERENT from
the elements it’s made from
Na + Cl2  NaCl
Mixtures
• Definition: 2 or more substances physically
combined
• Examples: fruit salad, salt water, steel, sand,
striped cloth, maple syrup
• Keep some (most) of their individual
properties.
• Classified by how well the substances are
mixed.
Heterogeneous Mixture
• The parts are noticeably different from one
another.
• fruit salad, sand, striped cloth
Homogeneous Mixture
• The parts are so evenly mixed the individual
parts are difficult or impossible to
distinguish.
• Sea water, steel, maple syrup
Special Types of Mixtures
1. SOLUTION
Formed when one substance DISSOLVES in
another
Kool-Aid, Antifreeze, Oxygen in water
Dissolved particles are so small:
– Do not separate over time
– If filtered, no particles are trapped
– Light will pass through without being scattered
2. SUSPENSION
A heterogeneous mixture that will separate
over time.
Muddy water, OJ with pulp, Apple cider
Dissolved particles are larger:
– Will separate over time
– If filtered, particles will be trapped
– Light passing into it is scattered in all directions
3. COLLOID
A mixture with larger particles than solution
but smaller than suspension
Fog, milk, styrofoam, blood, gelatin
Medium-sized particles
– Will not separate into layers
– A filter traps no particles
– Will scatter light in all directions
CHECK YOURSELF
Place the following in order from smallest to
largest particle size
SUSPENSION, SOLUTION, COLLOID
SOLUTION
SMALLEST
COLLOID
SUSPENSION
LARGEST
• Fill in the diagram
MATTER
PURE
SUBSTANCE
ELEMENT
MIXTURE
COMPOUND
HOMOGENEOUS
SOLUTION
COLLOID
HETEROGENEOUS
SUSPENSION
Physical Properties
Any characteristic that can be measured or
observed without changing the composition
of the material.
• VISCOSITY
– Ability to flow…slow flowing (syrup) = viscous
• CONDUCTIVITY
– Ability to conduct heat and/or electricity
• MALLEABILITY
– Ability to bend or be hammered without breaking
• HARDNESS
– Measures resistance to shape change
• Melting Point
– Temp at which particles become free to pass each
other
• Boiling Point
– Temp at which particles gain total freedom from
one another
• Density
– Amount of matter per unit volume
m
D
V
Uses of Physical Properties
1. Identify a substance:
 List of properties is like a fingerprint
2. Choosing a substance:
– Bulletproof vest?
– Artificial Heart?
3. Mixture Separation
– Filtration
Uses differences in particle size
– Distillation
Uses differences in boiling point
Divide this list into two groups:
•
•
•
•
Burning a marshmallow • Rusting car
Cutting paper
• Dissolving salt in water
Melting an ice cube
• Baking soda + Vinegar
Smashing a light bulb
•
•
•
•
Dissolving salt in water
Cutting paper
Melting an ice cube
Smashing a light bulb
• Burning a marshmallow
• Rusting car
• Baking soda + Vinegar
•
•
•
•
Dissolving salt in water
Cutting paper
Melting an ice cube
Smashing a light bulb
This list: All change the shape/form but the
substance remains the same
PHYSICAL CHANGES
Chemical Properties
Can be observed only when the substance is
changing into a different substance
• Burning a marshmallow
• Rusting car
• Baking soda + Vinegar
Two Names:
1. Flammability – Ability to burn in the
presence of oxygen
2. Reactivity – describes how readily a
substance combines chemically with
another
Sodium is reactive with water
Iron is not reactive with water
Magnesium is reactive with acid
Recognizing Chemical Change
• Color Change
– Copper turns green with age
– Rust
• Form a Gas
– Baking soda + Vinegar
– Magnesium + Acid
• Form a Precipitate
– lead nitrate + sodium iodide
Practice with P/C Changes
Shattering Glass
Sunburn
Bleaching clothes
Baking cookies
Folding laundry
Ripping your pants
Hydrogen peroxide on a cut
P
P
P
P
P
P
P
C
C
C
C
C
C
C