1. Chapter 11 Matter and Change 11.1 Describing Chemical Reactions
11.2 Types of Chemical Reactions
11.3 Reactions in Aqueous Solution

2. Define What Chemical Reactions are and give examples.
Write word equations and chemical equations using the proper symbols.
Balance Chemical Equations.

3. Introduction to Chemical Equations
Every minute of the day, chemical reactions take place—both inside you and around you.
After a meal, a series of chemical reactions take place as your body digests food.
Plants use sunlight to drive the photosynthesis.

4. All chemical reactions involve changing substances.
Introduction to Chemical Equations
All chemical reactions involve changing substances.
In a chemical reaction, one or more reactants change into one or more products.

5. Introduction to Chemical Equations
Chemists use a chemical equation—a quick, shorthand notation—to convey as much information as possible about what happens in a chemical reaction.

6. How do you describe what happens in a chemical reaction?
Introduction to Chemical Equations
Word Equations
How do you describe what happens in a chemical reaction?
The reactants are written on the left and the products on the right.
An arrow separates them.
You read the arrow as yields, gives, or reacts to produce.
Reactants → products

7. The burning of methane is a chemical reaction.
Introduction to Chemical Equations
Word Equations
The burning of methane is a chemical reaction.
Methane + oxygen → carbon dioxide + water

8. Introduction to Chemical Equations
A chemical equation is a representation of a chemical reaction using the formulas of the substances.
Here is a chemical equation for rusting:
Fe + O2 → Fe2O3

9. Chemical Equations Fe + O2 → Fe2O3
Introduction to Chemical Equations
Chemical Equations
A skeleton equation is an unbalanced chemical equation.
Fe + O2 → Fe2O3

10. Introduction to Chemical Equations
Physical states of substances are shown by putting a symbol after each formula.
(s) for a solid,
(l) for a liquid,
(g) for a gas, and
(aq) for a substance in an aqueous solution (a substance dissolved in water).
Fe(s) + O2(g) → Fe2O3(s)

11. Introduction to Chemical Equations
In many chemical reactions, a catalyst is added to the reaction mixture.
A catalyst is a substance that speeds up the reaction but is not used up in the reaction.
H2O2(aq) H2O(l) + O2(g)
MnO2

12. Symbols Used in Chemical Equations
Interpret Data
Symbols Used in Chemical Equations
Symbol
Explanation +
Separates two reactants or two products →
“Yields,” separates reactants from products
Use in place of → for reversible reactions
(s), (l), (g)
Designates a reactant or product in the solid state, liquid state, or gaseous state; placed after the formula
(aq)
Designates an aqueous solution; the substance is dissolved in water; placed after the formula
Indicates that heat is supplied to the reaction
A formula written above or below the yields sign indicates its use as a catalyst (in this example, platinum). Δ
heat Pt

13. Writing a Skeleton Equation
Sample Problem 11.1
Writing a Skeleton Equation
Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Write a skeleton equation for this chemical reaction.
Do it!!!

14. Solve Apply concepts to this situation.
Sample Problem 11.1
Solve Apply concepts to this situation. 2
Write the correct formula for each reactant and product.
Reactants
NaHCO3(s)
HCl(aq)
Products
NaCl(aq)
H2O(l)
CO2(g)

15. Solve Apply concepts to this situation.
Sample Problem 11.1
Solve Apply concepts to this situation. 2
Separate the reactants from the products with an arrow. Use plus signs to separate the reactants and the products.
NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

16. Balancing Chemical Equations
A chemical reaction is also described by a balanced equation in which each side of the equation has the same number of atoms of each element and mass is conserved.

17. Balancing Chemical Equations
balanced equation = each side of the equation has the same number of atoms of each element.
Bonds are broken, and new bonds are formed.
The atoms themselves are neither created nor destroyed; they are merely rearranged.
In any chemical change, mass is conserved.

18. To write a balanced chemical equation: write the skeleton equation.
Balancing Chemical Equations
To write a balanced chemical equation:
write the skeleton equation.
use coefficients to balance the equation so that it obeys the law of conservation of mass.
Make sure each side of the equation has the same number of atoms of each element.

19. C3H8(g) + O2(g) → CO2(g) + H2O(l)
Balance the following equation.
C3H8(g) + O2(g) → CO2(g) + H2O(l)

20. C3H8(g) + O2(g) → CO2(g) + H2O(l)
Balance the following equation.
C3H8(g) + O2(g) → CO2(g) + H2O(l)
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)

21. END OF 11.1