UNIT 2: ATOMS AND ELEMENTS

Physical and Chemical Change

PHYSICAL CHANGE

A change in shape or state of a substance

No evidence of a new material forming

Ex: Change in state

Anything that changed “what it looks like” not

“what it is”

PHYSICAL CHANGE

Examples

If a piece of paper is cut up into small pieces it still is

paper.

CHEMICAL CHANGE

A change in chemical properties of a substance

Means a new substance is formed

A chemical reaction has happened

Example:

If the same piece of paper is burned, it is broken up into different

substances that are not paper

CHEMICAL CHANGE

Evidence of a chemical reaction/change

1. A change in colour

2. A change in odor

CHEMICAL CHANGE

3. Fizzing or bubbling (a new gas being made)

4. A new solid forms from a mixture of liquids or

the mixture goes cloudy

This new solid is called a precipitate

CHEMICAL CHANGE

5. Change in energy

“energy” could be light, heat, or sound - think of the most

obvious change in energy reaction –an EXPLOSION!

TESTING FOR GASES

Oxygen

Flame re-ignites or glows

brighter

Hydrogen

Gas explodes with a “pop”

DETERMINE IF THE FOLLOWING SLIDES SHOW A

CHEMICAL OR PHYSICAL CHANGE