Unit 7: Chemical Reactions Writing word and skeletal equations

Chemical Reactions: When the atoms of one or more substances are rearranged to form different substances. CH4 + 2O2 ⇒ CO2 + 2H2O Reactants: Starting substances Products: Ending Substances

Chemical Reaction Symbols: Write these in your flipbook +  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)

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

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

Key words for chemical reactions: 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)

Change in Energy 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

Odor Change: Color Change: Production of a gas: Rotting, baking, cooking, etc. 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 Production of a gas: Formation of bubbles, etc This is not caused by heating or boiling a substance.

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.

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

Skeletal Equations Chemical reactions using chemical symbols/formulas and chemical reaction signs. Written from a word equation: Solid Aluminum reacts with liquid bromine to form solid aluminum bromide. Al(s) + Br2(l) AlBr3(s)

Key Words: Remember the key words give us information about the reaction Carbon monoxide gas and oxygen gas react to yield carbon dioxide gas. CO(g) + O2(g) CO2(g)

States of Matter: (write these in your flipbook) Solid (s) Liquid (l) Gas (g) Aqueous (aq)

Diatomic Elements: CO(g) + O2(g) CO2(g) Al(s) + Br2(l) AlBr3(s) Notice that some of the elements have a 2 after them in their skeletal equations: These are called diatomics: These are elements that cannot exist in nature a single atom. If they are NOT in a compound, then they must be bonded to another atom of the same element  Cl + Cl = Cl2 CO(g) + O2(g) CO2(g) Al(s) + Br2(l) AlBr3(s)

Diatomic Elements: Check and make sure these are correct in your flipbook There are 7 diatomics:

Practice Problems: I will complete the first one with you, then you will try the rest on your own. You may write these right on your table, IF and ONLY IF you have a neon expo marker, if not please complete them on a separate sheet of paper.

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

Practice: Solid zinc reacts with aqueous sulfuric acid to form hydrogen gas and solid zinc (II) sulfate. Solid barium hydroxide decomposes into solid barium oxide and water.