Chemistry
11.1
“Describing Chemical Changes”
Review
A. Reactants  Products
B. Dalton’s Theory…
“As reactants are converted to
products, the bonds holding the atoms
together are broken and new bonds are
formed.”
C. Law of Conservation of Mass…
“Mass is neither created nor destroyed.”
II. Equations
A. Word Equations
1. Def – words used to describe a chemical
reaction.
-no #’s are involved
2. Ex: Iron + Oxygen  Iron (III) Oxide
3. Ex: Hydrogen Peroxide  Water + Oxygen
4. Ex: Methane + Oxygen  Carbon Dioxide + water
5. What is the word equation for…Pure
copper can be produced by heating
copper (II) sulfide in the presence of
diatomic oxygen from the air. Sulfur
dioxide gas is also a product in this
reaction.
Copper II Sulfide + Oxygen  Copper + Sulfur Dioxide
B. Chemical Equations
1. Def – Using chemical symbols to
write a chemical formula.
- #’s are involved
2. Ex: Fe + O2  Fe2O3
-this is a skeleton equation b/c it is not
balanced
C. Balanced Chemical Equations
1. Follows the Law of Conservation of
Mass.
2. 4 Fe + 3 O2  2 Fe2O3
III. Symbols used in chemical equations
+
Used to separate reactants or
products

“Yields” separates products and
reactants
(s)
(l)
(g)
(aq)
Solid state of matter
∆ / heat
Pt, H2SO4
Liquid state of matter
Gaseous state of matter
Aqueous solution – dissolved in
water
Heat is supplied in the reaction
A formula written above or below
the yield sigh indicates it is a
catalyst