Property = a characteristic that gives
a substance identity
Chemical
Properties and
Changes
Properties of Vinegar:
- clear liquid
- density is 1.08 g/mL
-strong odor
- reacts with baking soda
- acidic
Composition
Physical
Property
= the ingredients or make-up of
a substance, often represented
by a chemical formula
Water is composed of Hydrogen and Oxygen
Emeralds are composed of Al, Be, Si and O
Chemical
Property
• can be observed
without changing
composition
• Only can be observed
when composition
changes.
• depends only on
the substance
itself
• “depends on its
reaction with other
matter”
Diamonds are composed of Carbon only
Methanol / Water
Physical
Property
Chemical
Property
• can be described
using the word
“is”
• can be described
using the word
“can” or “will”
• (or will not, can not)
Important Physical Properties:
•
•
•
•
•
Color
Opacity
Density
Magnetism
Conductivity
– (ability to conduct heat or electricity)
• Solubility
– (ability to form a solution in water or other solvent)
• Crystal Form
Methanol / Water
– (grain size, geometric shape of crystal)
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What is a
Chemical
Reaction?
There is only one
chemical property:
REACTIVITY
Chemical Reaction:
…whether something will react with (have a
chemical reaction with) another substance.
…a rearrangement of the atoms in a
substance to produce new substances
All chemical reactions can be written as:
So, (review):
chemical equations:
REACTIVITY
for example:
Methanol + Oxygen 
Carbon Dioxide + Water
REACTANTS
PRODUCTS
is a chemical property
or:
CH3OH
+
O2

REACTANTS
CO2 +
2H2O
PRODUCTS
…that describes whether something will have
a chemical reaction (chemical change) with
another substance.
pH: An important chemical property.
Examples of
Reactivity:
pH = a measure of how acidic or basic a substance is.
(it describes a reaction with water.)
• Reaction with…____
• Flammability
(reaction with O2)
• pH
(reaction with
water…whether
something is an ‘acid’ or
a ‘base’)
ACIDS
BASES
• Turn litmus paper red
• React with bases to
form salts and water
• Taste Sour
• Turn litmus paper blue
• React with acids to
form salts and water
• Taste Bitter
Solder / Mg
2
Which are Physical Properties?
Which are Chemical Properties?
pH = a measure of how acidic or basic a substance is.
(it describes a reaction with water.)
ACIDS
Physical
Change
• No new substances are
formed.
• No change in chemical
formula
Examples;
- Crushing into Powder
- All Phase Changes
BASES
Chemical
Change
• = “chemical reaction”
• New substances are
formed.
• Chemical Formulae are
new or changed,
Examples;
- Wood Burning (Combustion)
-Iron Rusting (Oxidation)
Ice Melting: Chemical or Physical Change?
•
•
•
•
•
•
•
•
•
•
Hardness……………………
Color……………………….
Reactivity with HCl……….
Magnetism………………...
Density…………………….
pH………………………….
Flammability………………
Boiling Point………………
Corrosiveness………………
Melting Point………………
Physical
Physical
Chemical
Physical
Physical
Chemical
Chemical
Physical
Chemical
Physical
Q: How can we tell if a chemical change has occurred?
A: Look for evidence…
5 Signs of a Chemical Reaction:
•
•
•
•
•
Formation of a gas
Formation of a solid
Unpredictable Color Change
Radiant Energy (Light)
Thermal Energy (Heat)
Phase Changes and Kinetic Theory
• Composition does not change; it is still water (H2O). No
new substances are formed, so no chemical change.
PHASE CHANGE = PHYSICAL CHANGE
3
When a candle melts, some of the wax
turns to a liquid and runs down the
side. Is this a chemical change or a
physical change? Why?
• Does the candle become a
new substance?
• It was wax; it is still wax;
liquid wax is still wax
Physical Change
Is lighting a match a chemical
change
Enough!
or a physical change? Why?
• Is a new substance
produced?
• Does a color change
occur?
• Is heat and light given
off?
• Is a gas produced?
Chemical Change
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