Physical and Chemical Properties and Evidences of Chemical Reactions
Physical Property
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A characteristic of a substance that does
not involve a chemical change, such as
density, color or hardness
Color, shape, odor, weight, volume,
texture, state and density
Apple: don’t have to change
it to see that it is round and red
General Physical Properties
• Size
• Shape
• Color
• Smell
• Weight or Mass
• Volume
Specific Physical Properties
• Thermal Conductivity
• Solubility
• Ductility
• Magnetism
• State
• Density
• Malleability
Thermal Conductivity
• The rate at which a substance
transfers heat.
• Example: Styrofoam is a poor
conductor
Solubility
• The ability of a substance to dissolve
in another substance
• Example: Flavored drink mix dissolves
in water
Magnetism
• The property of some materials to
attract iron or objects containing
iron.
• Example: lodestone is a naturally
magnetic rock
Specific Physical Properties Continued:
State or Phase of Matter
• The physical form in which a substance
exists, such as a solid, liquid or gas.
• Example: Ice is water in the solid state
Density
• The mass per unit volume of a substance.
• Example: Lead is very dense,
so it makes a good sinker
for a fishing line
Malleability
• The ability of a substance to be rolled or
pounded into thin sheets
• Example: Aluminum can be rolled into
sheets to make foil
Physical and Chemical Properties and Evidences of Chemical Reactions
Chemical Property
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Describes a substance’s ability to
participate in chemical reactions
Example: When wood is burned, ash
and smoke are created. The new
substances have very different
properties than the original wood
Specific Chemical Properties
Flammability
• The ability of a substance to burn.
• Example: Wood has the property of
flammability. However, ash and
smoke can’t burn, so they have the
chemical property of non-flammability.
Reactivity
• The ability of two or more substances to
combine and form one or more new
substances
• Example: Metal + Oxygen = Rust
Comparing Chemical and Physical Properties
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Physical properties are easy to observe.
You can measure the density or the
hardness without changing anything.
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Chemical properties are harder to
observe. You can only see that wood is
flammable when it is actually burning.
BUT that piece of wood is still considered
flammable even when it’s not burning.
Evidences of a Chemical
Reaction
1) Color Change
o An usual color change can signal that a
new substances has formed
i. Example: blue + yellow liquid
combined should turn green, a
chemical reaction might make this
turn red.
o A color change does not always indicate
a chemical reaction has occurred
2) A solid may appear (Precipitate)
o A solid that form from solution during a
chemical reaction is called a precipitate
o The precipitate is a new/different
substances and does not dissolve in the
solution; it floats or sinks
3) A gas is produced
o If the reaction occurs in liquid, you may
see bubbles
o Gas may or may not have an odor
4) Temperature Change
o Increase or decrease in temperature is
also an evidence of a chemical change
o The heat would be generated from the
energy from the reaction, not an
external heat source
5) Irreversible
o With a chemical reaction, the outcome
is very difficult or impossible to
reverse.
o Example: Water can melt and go
through several different state
changes. It can be ice, water or steam
and to move from one state to another
it is frozen, melted or boiled. These are
all easily reversible. In a chemical
reaction there is a change to the
chemical composition of the
substances which is not so easy to
reverse.
Physical and Chemical Properties and Evidences of Chemical Reactions