1. Changes in Matter

2. Physical Change
The form or appearance of the sample may change but the identity remains the same.
Crumpling
Cutting, crushing, grinding,tearing
Phase changes
Dissolving

3. Representing Change By the Way Use “equations” to show change.
Substances Before  Substances After
By the Way
In a physical change, you have the same stuff before & after. The formulas match!

4. Dissolving Dissolving is a physical change.
Think of sugar in water. You still have sugar – you just spread it out and put water molecules in between.
C6H12O6(s)  C6H12O6(aq) =

5. Dissolving
source

6. Phase Changes Phase changes are physical changes.
No new substance is created (chemical formula stays the same)
ice melting: H2O(s)  H2O(l)
water boiling: H2O (l)  H2O(g)

7. Chemical Change
In a chemical change the identity of the matter is changed.
A new substance with unique properties is formed.
The chemical formula changes.
Ex: 2H2O(l)  2H2(g) + O2(g) 

8. Chemical decomposition of water.
2H2O(l)  2H2(g) + O2(g)
Decomposition = Reaction where a molecule breaks down into simpler substances.
source

9. 2H2O(l)  2H2(g) + O2(g)

10. Burning Common name for an oxidation reaction.
Burning means reacting with oxygen.
Burning is a chemical change, because the original substance is changed into new kinds of matter.
Ex: CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
Formulas don’t match!

11. CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
Formulas don’t match!
source

12. Other Chemical Changes
Cooking
Fermentation
Corrosion
Rotting
Explosion
Synthesis

13. Evidence of Chemical Change
Produce Heat
Produce Light
Evolution of a Gas
Formation of a Precipitate
Change in Properties …meaning…
Create something NEW

14. Conservation of Mass Massreactants = Massproducts
Mass is neither created nor destroyed.
Mass is conserved.
Massreactants = Massproducts
Massbefore = Massafter
# of atoms before = # of atoms after