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