1. Writing and Balancing Chemical Equations
The Law of Conservation of Mass:
Writing and Balancing Chemical Equations
Reactant 1 + Reactant Product 1 + Product 2
Propane combusts in the presence of oxygen to produce water and carbon dioxide.
C3H O2 → 4H2O + 3CO2
Photo by Dinshaw Dadachanji

2. How would you describe a chemical reaction?
Pb(NO3) KI
2KNO PbI2
Substance(s) react to form a new combination of substances

3. What is a skeleton equation?
A skeleton equation states the reactants and the products before the equation is balanced.
Important Fact: The skeleton equation and the balanced equation CAN be the same.

4. What are the reactants in a
chemical reaction?
Reactants are the substances that interact at the beginning of a reaction.
Pb(NO3) KI
2KNO PbI2

5. Where are reactants written in a chemical equation?
Reactants are on the LEFT side.
Reactants
Pb(NO3) KI
2KNO PbI2

6. What are the products in a
chemical reaction?
Products are the substances that are formed during the reaction.
Pb(NO3) KI
2KNO PbI2

7. Where are products written in a chemical equation
Products are on the RIGHT side.
Products
Pb(NO3) KI
2KNO PbI2

8. What words are used to show the reactants interacting in a chemical reaction?
Reactants are easy to spot when you see, “reacts with” in the problem, but any chemical change vocabulary word can be used.
Examples:
Burns/
Combusts
Rusts
Decomposes
Corrodes

9. What words are used to show the creation of products in a chemical reaction?
Products are “produced” during a chemical reaction, but there are several words that can describe the formation of products.
Examples:
Produces
Forms
Yields