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•Property of matter that describes a
substances ability to participate in chemical
reactions. (Change into new matter.)
–Flammability
•ability to burn
•Burning wood creates ash and smoke
–Reactivity
•ability of two or more substances to combine and
form a new substance
•Oxygen and iron create rust
• Physical properties may be observed
without changing the identity of the
substance.
– Density, Hardness, Color
• Chemical properties can not be observed
until the chemical reaction takes place.
– A piece of wood is flammable even when it is
not burning, but must be burning to observe
this property
• Properties most useful in identifying a
substance.
– Always the same no matter the size of the
sample
– Physical properties
• Density, Hardness
– Chemical Properties
• Flammability, reactivity
• Used to identify and classify substances
• When one or more substances are
changed into an new substance
– Learn about chemical properties through
chemical changes
– Examples:
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Digestions
Burning wood
Rust
Soured milk
• Ingredients combine to form a new substance
– Baking a cake
– Change in color, odor
– Production of heat, sound, light
– Change the identity of the matter involved
• This makes them very hard to reverse
• Some chemical changes can be reversed
– Water split back into oxygen and hydrogen using electric
current- called electrolysis
• Did the composition change?
– Composition is the type of matter that makes up an
object and the way that matter is arranged
• Chemical changes alter the composition of the
substance.
• Many physical changes may be easily reversed
– Melted ice cube can be frozen again
• Chemical Changes are not easily reversed
– Water separated into hydrogen and oxygen