1. Describing Chemical Reactions
Chapter 6
Section 2

2. Chemical Formulas
Let’s remember what chemical formulas are and what all of the letters and symbols mean. . .

3. Chemical Equations Short and easy way to show a reaction!
Chemical formulas and symbols to summarize a reaction.
Reactant + Reactant  Product + Product

4. Let’s Review… What are 4 types of evidence that a chemical reaction has occurred?

5. Conservation of Matter
In a chemical reaction, the total mass of the reactants must equal the total mass of the products.
The number of atoms will stay the same!

6. Open v. Closed System Open System
Matter can enter from or escape to the surroundings
Closed System
Matter is not allowed to enter or leave

7. Balancing Chemical Equations
A chemical equation MUST show the same number of each type of atom on both sides of the equation.
H2 + O2  H2O
Count your atoms!
Count your atoms again!
Is the equation balanced?
# of hydrogen atoms on the reactant side:
# of oxygen atoms on the reactant side:
# of hydrogen atoms on the products side:
# of oxygen atoms on the products side:

8. H2 + O2  H2O

9. Let’s Practice!
Sn + Cl2  SnCl2
Sn:
Cl:

10. Let’s Practice!
Na + O2  Na2O
Na: O:
Na + O2  Na2O

11. Let’s Practice! Na + MgF2  NaF + Mg Na + MgF2  NaF + Mg Na: Mg: F:
Download and open the document from Moodle called “Chemical Equations”
Na + MgF2  NaF + Mg
Na:
Mg: F:
Na + MgF2  NaF Mg

12. Steps for Balancing Equations
Synthesis
Two or more elements or compounds combine to make a more complex substance.
Decomposition
Compounds break down into simpler products.
Replacement
One element replaces another in a compound or two elements trade places.

13. Steps for Balancing Equations
Write the equation
Count the atoms on both the reactant and product side
Use Coefficients to Balance the Atoms
Look back and Check your work.