ChemistryPhysical & Chemical Change

Chemists classify changes in matter into two categories:

Physical changes

Chemical changes

Physical Change

No new substance is produced.

New physical properties MAY appear, but the particles of the starting substance are not changed.

In a physical change, the matter involved can experience a change in one of the following criteria:

Change in SIZE (cutting a gold block in half)

Change in SHAPE (making a paper airplane)

Change in STATE (ice cube melting)

Making a SOLUTION (salt dissolved in water)

No new substance is made, and all changes are reversible.

Chemical Change

The starting substance is changed to produce something totally new that shows new properties that were not there before.

In a chemical change, the matter involved can experience a change in one of the following criteria:

Change in COLOUR (iron nail producing red rust)Change in ODOUR (garbage rotting)Change in TEMPERATURE (cold pack)LIGHT IS GIVEN OFF (fire-fly)BUBBLES OF A GAS are formed (bubbles not

caused by heat)NEW SOLID is made from mixing two solutions

(precipitate)

Chemical changes are difficult to impossible to reverse.