•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 two or more substances are changed into an new substance– Learn about chemical properties through

chemical changes– Examples:

• 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

• 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