1. Changing Matter Matter can be changed two ways: Physically Chemically
October 10, 2006
Changing Matter
Matter can be changed two ways:
Physically
Physical reaction
Physical change
Chemically
Chemical reaction
Chemical change

2. Physical Changes Do NOT CHANGE THE TYPE OF MATTER
Nothing new or different is formed
Could be a change in:
Mass
Volume
Density
Change in state
Color
Shape
Size

3. Examples of Physical Changes
Boiling
Freezing
Dissolving
Breaking
Making a mixture
2 or more types of matter (substances) mixed together
Not in specific amounts
Can be separated physically

4. Chemical Changes
Atoms have electrons arranged in energy levels or energy shells
Electrons in the last (outermost) shell are called valence electrons
Valence electrons let atoms bond with other atoms
Ionic bonding
Gaining or losing electrons
Covalent bonding
Sharing electrons

5. Chemical Changes Atoms that bond form molecules
May be the same type of atom or,
Different types of atoms
Different types  compounds

6. Chemical Changes Molecules can bond and “unbond”
Atoms can re-arranged in different combinations
For example:
CaCO3 (1 atom Ca, 1 atom C, 3 atoms O)
Add heat to re-arranged the atoms:
CaO
CO2

7. Chemical Changes Evidence of a chemical reaction Formation of gas
Formation of precipitate
Change in color
Change in energy
Endothermic
Absorbs heat energy (gets cold)
Exothermic
Releases heat energy (gets hot)

8. Chemical Changes Chemical reactions can be represented by equations
CaCO3  CaO + CO2
Reactants Products

9. Chemical Changes Atoms are re-arranged, NOT created or destroyed
Law of Conservation of Matter
Law of Conservation of Mass

10. Chemical Changes Matter is conserved  type of atoms does not change
Nothing is created or destroyed
Mass is conserved  amount of atoms cannot change

11. Chemical Changes To show conservation of mass  Balance equations
Make sure there are the same number of each type of atom in the products and in the reactants

12. The equation for the burning of methane gas in oxygen is:
Balancing Equations
The equation for the burning of methane gas in oxygen is:
CH4 + 2 O2 → CO2 + 2 H2O
Subscript
Shows # of atoms
Coefficient
Shows # of molecules

13. Balancing Equations 1 C  1 C 4 H  4 H 4 O  4 O
No subscript or coefficient is understood to be 1
CH4 + 2 O2 → CO2 + 2 H2O =
C1H4 + 2 O2 → C1O2 + 2 H2O1
1 C  C
4 H  H
4 O  O

14. Types of Chemical Reactions
Synthesis Reaction 2 or more simple substances combine to form a more complex substance.
A+B  AB
Decomposition Reaction
A more complex substance breaks down into its more simple parts
AB  A + B

15. Types of Chemical Reactions
Replacement Reactions
AB + CD  AD + CD