1. Chapter 6 Chemical Reactions and Equations
6.1 Chemical Equations
6.2 Types of Reactions
6.3 Nature of Reactions

2. 6.1 Chemical Equations Objectives
Relate chemical changes and macroscopic properties.
Demonstrate how chemical equations describe chemical reactions.
Illustrate how to balance chemical reactions by changing coefficients.

3. Recognizing Chemical Reactions
Chemical reactions occur all around you and within you.
Evidence:
Color change
Odor
Temperature change
Gas production
Precipitate

4. Writing Chemical Equations
Reactant- substance that undergoes a reaction, the starting substance(s).
Product- the new substance formed from the reactants.
Rust
Iron and oxygen react to form Iron (III) oxide

5. Writing Chemical Equations
Word Equations
Chemical Equations
First lets practice writing formulas.
You MUST be able to write formulas in order to write the equations

6. Word Equation Word equation Word equations are the simplest form
Vinegar + Baking soda  sodium acetate + water + carbon dioxide
Can be using common names or the chemical names.
Acetic acid + sodium hydrogen carbonate  sodium acetate + water + carbon dioxide
Word equations are the simplest form

7. Chemical Equations
Uses the chemical formulas for the reactants and products.
This is why you must be able to write formulas.
Baking soda and vinegar
HC2H3O2 + NaHCO3  NaC2H3O2 + H2O + CO2

8. Chemical Equations
It is also important to know the state the compounds are in
(g) – gas
(s) – solid
(l) – liquid
(aq) – aqueous
HC2H3O2 (aq) + NaHCO3 (s)  NaC2H3O2 (aq) + H2O (l) + CO2 (g)

9. Equations and Energy
Some chemical reactions require an energy input to occur
Some chemical reaction produce energy
Energy can be in the form of electricity (input), heat or light.
Endothermic reaction- absorbs energy
Exothermic reaction- gives off energy

10. Balancing Chemical Equations
Balanced equation for the reaction of iron and chlorine:
2Fe (s) + 3 Cl2 (g)  2FeCl3 (s)
To balance an equation you must first find the correct coefficients- the number written in front of a reactant or product; tells the smallest number of particles of the substance involved in the reaction.

11. Steps for balancing equations
Write the skeleton equation for the reaction.
Count the atoms of the elements in the reactants.
Count the atoms of the elements in the products.
Change the coefficients to make the number of atoms of each element equal on both sides of the equation.
Write the coefficient in their lowest possible ratio.
Check your work.