Changes in Matter

1
Changes in Matter

• Why do properties change?

2
Changes in Matter

• Iron Sulfide Video
• http//www.westlake.k12.oh.us/whsteachers/planisek
  /VideosAnimations/Mixtures_and_Compounds.mov

3
Physical Changes

• The properties of a substance change, but the
  composition of that substance does not

4
Chemical Changes

• A substance reacts with another substance and one
  or more new substances is (are) formed

5
Indicators of Chemical Change

• Color Change
• Copper turns green when it is exposed to oxygen
• Formation of a material with a different color
  indicates that a new substance with different
  properties has been formed

6
Indicators of Chemical Change

• Production of a Gas
• Bubbles indicate that a new substance with
  different properties from the original substances
  is formed

7
Indicators of Chemical Change

• Formation of a Precipitate
• Two liquids form a solid when mixed
• The new substance has different properties from
  the original substances

8
Indicators of Chemical Change

• Energy given off in the form of heat or light
• Heat Energy Given Off ? Exothermic
• Energy in some other form than heat is given off
  ? Exergonic

9
Conservation

• The amount of a substance must remain the same
  during a process
• Whatever is there at the beginning has to be
  there at the end, even if it looks a little
  different.

10
Conservation of Mass

• The total amount of mass present before a
  chemical reaction occurs must be the same as the
  amount of mass present after the reaction occurs
• No change in the amount of total mass occurs
  during a chemical reaction

Antoine Lavoisier 1743-1794