1. 2.4 Chemical Changes Chemical Property
ability to undergo a chemical change; “reactivity”; “behavior”
observed when matter changes its composition
can be used to identify matter
e.g., burn, rot, rust, decompose, ferment, explode, corrode, oxidize, etc… 1

2. 2.4 Chemical Changes Chemical Change
change in the composition of matter
a.k.a. chemical reaction
REACTANT(S)  PRODUCT(S)
starting material finishing material;
“new” substance 2

3. Recognizing Chemical Changes
Possible “clues” to a chemical change:
Transfer of energy (i.e. light &/or heat given off)
Change in color
Production of gas
Formation of precipitate (a solid that forms out of a liquid)
Clues do not necessarily confirm chemical change. 3

4. Conservation of Mass The Law of Conservation of Mass
Mass is neither created nor destroyed in any chemical reaction.
Mass of reactants = mass of products 4

5. Conservation of Mass 5

6. 6

7. Conservation of Mass 7