Notes
Slide Show
Outline
1
Changing Matter
  • Matter can be changed two ways:
    • Physically
      • Physical reaction
      • Physical change
    • Chemically
      • Chemical reaction
      • Chemical change
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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
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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
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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
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Chemical Changes
  • Atoms that bond form molecules
    • May be the same type of atom or,
    • Different types of atoms
  • Different types à compounds
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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
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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)
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Chemical Changes
  • Chemical reactions can be represented by equations


  • CaCO3 à CaO + CO2
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Chemical Changes
  • Atoms are re-arranged, NOT created or destroyed
    • Law of Conservation of Matter
    • Law of Conservation of Mass
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Chemical Changes
  • Matter is conserved à type of atoms does not change
    • Nothing is created or destroyed


  • Mass is conserved à amount of atoms cannot change
    • Nothing is created or destroyed
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Chemical Changes
  • To show conservation of mass à Balance equations
    • Make sure there are the same number of each type of atom in the products and in the reactants
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Balancing Equations
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Balancing Equations
  • No subscript or coefficient is understood to be 1
  • CH4 + 2 O2 → CO2 + 2 H2O =
  • C1H4 + 2 O2 → C1O2 + 2 H2O1


          • 1 C    à     1 C
          • 4 H    à     4 H
          • 4 O    à     4 O
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Types of Chemical Reactions
  • Synthesis Reaction
    2 or more simple substances combine to form a more complex substance.
  • A+B à AB
  • Decomposition Reaction
    • A more complex substance breaks down into its more simple parts
    • AB à A + B
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Types of Chemical Reactions
  • Replacement Reactions
  • AB + CD à AD + CD