1. Warm Up: Write in your notes
What do you already know about chemical and physical changes?
What do you already know about chemical reactions?

2. Chapter 9: Chemical Reactions
Writing word and skeletal equations

3. Chemical Reactions:
When the atoms of one or more substances are rearranged to form different substances.
CH O ⇒ CO H2O
Reactants: Starting substances
Products: Ending Substances

4. Chemical Reaction Symbols:
+  Separates two or more reactants or products
⇒  Separates reactants from products
↔  Separates reactants from products and indicates a   reversible reaction
(s)  Identifies a solid state
(l)  Identifies a liquid state
(g)  Identifies a gaseous state
(aq)  Identifies a water solution (Aqueous)

5. Law of the Conservation of Mass
Mass is neither created nor destroyed during a chemical reaction

6. Signs of a chemical change:
Energy change
Color change
Odor change
Production of gas
Formation of a solid (precipitate)

7. Energy Change Energy either being gained or released as heat or light
Two types:
Exothermic: Energy released by the reaction
We will see light or feel heat
Endothermic: Energy gained by the reaction
We will feel the reaction getting cold

8. Color Change:
Typically associated with another sign of a chemical change
The formation of a solid/percipitate
Note: Mixing of colors, diluting, etc, are not signs of a chemical change

9. Odor Change:
Rotting, baking, cooking, etc.

10. Production of Gas Formation of bubbles, etc
This is not caused by heating or boiling a substance.

11. Formation of a Solid:
A solid is formed during the reaction, when adding or taking away energy from the rxn.
This solid is known as a precipitate.
It is NOT mean the freezing of a liquid into a solid.

12. Word Equations: Chemical Rxn in word format:
Solid Aluminum and liquid bromine react to produce solid aluminum bromide.

13. Skeletal Equations
Chemical reactions using chemical symbols and an arrow.
Al(s) + Br2(l) AlBr3(s)

14. Word and Skeletal Equations:
They are two different ways to write the same thing.
Solid Aluminum and liquid bromine react to produce solid aluminum bromide.
Al(s) + Br2(l) AlBr3(s)

15. Key Words: Reacts: tells us what is reacting with what
We use a + to represent reacts/reacts with
Yields/To form: tells us what the product(s) is
We use an to represent yields/produces/to form
* We state the state of the matter for each substance. (solid, liquid, gas, or aqueous)

16. Key Words:
Carbon monoxide gas and oxygen gas react to yield carbon dioxide gas.
CO(g) + O2(g) CO2(g)

17. States of Matter: Solid (s) Liquid (l) Gas (g) Aqueous (aq)
Use the context clues of the word equation to determine the states of matter of the reactants and products.

18. Diatomic Elements: CO(g) + O2(g) CO2(g) Al(s) + Br2(l) AlBr2(s)
Notice that some of the elements have a 2 after them in their skeletal equations:
These are called diatomics:
These are elements exist in nature as two atoms of the same element together, ONLY when they are not bonded to another element.
CO(g) + O2(g) CO2(g)
Al(s) + Br2(l) AlBr2(s)

19. Diatomic Elements:
There are 7 diatomics:

20. Practice:
Aqueous Sodium hydroxide reacts with aqueous calcium bromide to form aqueous sodium bromide and solid calcium hydroxide.

21. Practice:
Solid zinc reacts with aqueous sulfuric acid to form hydrogen gas and solid zinc (II) sulfate.

22. Practice:
Fe(s) + O2(g) Fe203(s)

23. Practice:
Solid barium hydroxide decomposes into solid barium oxide and water.