1. PHYSICAL & CHEMICAL CHANGES
Objectives:
Compare and contrast physical and chemical changes
Identify examples of physical and chemical changes

2. Why do I care?
Physical and Chemical changes occur around us everyday! Understanding them will help us better understand our world.

3. Changes in Matter Change: the act of altering a substance
In science, we talk of two types of changes:
physical
chemical 3

4. Physical Change
Physical change: a change that occurs that does not change the identity or make up of the substance
Change in state or phase (Freezing, boiling, melting, sublimating)
Changing shape (cutting, folding, twisting, bending)
Dissolving 4

5. Physical Changes
Physical changes are changes that alter the size, shape, location or physical state of a substance but not its chemical state.
Its still H2O- frozen in snowflakes, as liquid in raindrops, or as a gaseous water vapor, it’s chemical formula has not changed.

6. Examples
A physical change in a substance doesn't change what the substance is.
Cutting, folding, or crumpling paper –
A physical change in the shape and size of the paper. However, it is still paper!
Dissolving sugar in iced tea-
Sugar is still C6H12O6 but now it is spread out in the liquid, it still tastes just as sweet!

7. What Other Kinds of Changes Are Physical?
Cutting
Tearing
Shredding
Shrinking
Enlarging
Change in Phase
Relocating
Rotating
Molding (shaping)

8. Chemical Changes
Chemical change: a change that occurs causing the identity of the substance to change
Burning
Chemically digesting food (acid and bile)
Reacting with other substances
A chemical change is also called a chemical reaction 8

9. Chemical Changes
Chemical changes are changes that alter the chemical make up of the substance.
New matter is formed with properties that are different than those of the original matter.

10. Chemical Changes
If you end up with a chemical or chemicals that you did not start with. . .
It is a chemical change!

11. Chemical Changes A chemical change is not easily reversed.
Difficult to reverse/change back
Easy to reverse/change back

12. Signs That a Chemical Change has occurred
Creation of a gas (bubbles)
Creation or loss of heat
Burning
Rotting/molding
Breaking down (decomposition)
Precipitation
Cooking
Rusting (oxidation)

13. Heat and light are often evidence of a chemical change.

14. The strike of a match is a chemical change due to the reaction of the chemicals with oxygen.

15. Burning wood turns to charcoal and ashes. This is a chemical change.

16. Is it Physical or Chemical?
Change
Physical
Chemical
Melting cheese
Burning wood
Milk souring
Folding up paper
Bicycle rusting 16

18. Start physical changes challenge Powerpoint