 What do you already know about chemical and physical changes?  What do you already know chemical reactions?

Writing word and skeletal equations

 When the atoms of one or more substances are rearranged to form different substances. CH 4 + 2O 2 ⇒ CO 2 + 2H 2 O Reactants: Starting substances Products: Ending Substances

+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)

Mass is neither created nor destroyed during a chemical reaction

1. Energy change 2. Color change 3. Odor change 4. Production of gas 5. Formation of a solid (precipitate)

 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

 Typically associated with another sign of a chemical change ◦ Mixing of colors, diluting, etc, are not signs of a chemical change

 Rotting, baking, cooking, etc.

 Formation of bubbles, etc ◦ This is not caused by heating or boiling a substance.

 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.

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

 Chemical reactions using chemical symbols and an arrow. Al(s) + Br 2 (l) AlBr 2 (s)

 They are two different ways to write the same thing. Solid Aluminum and liquid bromine react to produce solid aluminum bromide. Al(s) + Br 2 (l) AlBr 2 (s)

 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

 Carbon monoxide gas and oxygen gas react to yield carbon dioxide gas. CO(g) + O 2 (g) CO 2 (g)

 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.

 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) + O 2 (g) CO 2 (g) Al(s) + Br 2 (l) AlBr 2 (s)

 There are 7 diatomics:

 Aqueous Sodium hydroxide reacts with aqueous calcium bromide to form aqueous sodium bromide and solid calcium hydroxide.

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

 Fe(s) + O 2 (g) Fe (s)

 Solid calcium oxide reacts with water to form solid calcium hydroxide.

 Gaseous sulfur dioxide and oxygen gas react to form sulfur trioxide gas.

 Solid sodium reacts with chlorine gas to form solid sodium chloride.

NaCl(aq) + AgNO 3 (aq) NaNO 3 (aq) + AgCl(s)

 Please complete your ticket out the door, and turn into me before packing up.  HINT: Make sure you know the 7 diatomic elements tomorrow when you come in the door!