1. Chemical Changes Chemical Change:
One or more new substances are formed.
The substances formed have different properties (colour, odor, texture, taste, luster, etc.)
New and different bonds are formed.
The same number and type of atoms are present after a chemical they are just in a new order.
Before the reaction.
During the reaction.
After the reaction.

2. Think About It!
The average piece of wood is made of many glucose (sugar) molecules all bound together.
When glucose is burned (combined with oxygen) the word equation is:
glucose + oxygen  carbon dioxide + water
O—O + +
Does it look to you as though there are the same types and numbers of atoms at the beginning of the reaction as there is at the end of the reaction?

3. SMART LESSON: Chemical Equations and Atom Numbers
Word equations do not tell us anything about the number of atoms involved in a chemical reaction. In order to have that type of information we need to look at a reaction’s chemical equation.
The chemical equation is:
C6H12O6 + 6O > 6CO2 + 6H2O
(glucose)
SMART LESSON: Chemical Equations and Atom Numbers

4. Clues to Indicate a Chemical Reaction
brand new colour
new odor
gas is created
precipitate forms
light is given off
change in temperature

5. Other Examples of Chemical Changes
Cooking
Rotting
Rusting
Exploding