Types of Reactions You need to be able to identify each type. Synthesis reactions Decomposition reactions Single displacement reactions Double displacement reactions Combustion reactions You need to be able to identify each type.

1. Synthesis Example C + O2 O C +  O C General: A + B  AB

Ex. Synthesis Reaction

Practice Predict the products. Na(s) + Cl2(g)  Mg(s) + F2(g)  Al(s) + F2(g)  2 2 NaCl(s) MgF2(s) 2 3 2 AlF3(s) Now, balance them.

2. Decomposition Example: NaCl  Cl Na Cl + Na General: AB  A + B

Ex. Decomposition Reaction

Went from neutral (0) to (+2) Went from (+2) to Neutral (0) 3. Single Displacement Example: Zn + CuCl2 Zn was oxidized Went from neutral (0) to (+2)  Zn Cl Cu + Cl Zn Cu + Cu was reduced Went from (+2) to Neutral (0) General: AB + C  AC + B

Ex. Single Replacement Reaction

Single Replacement Reactions Write and balance the following single replacement reaction equation: Zn(s) + HCl(aq)  ZnCl2 + H2(g) 2 NaCl(s) + F2(g)  NaF(s) + Cl2(g) Al(s)+ Cu(NO3)2(aq) 2 2 2 3 3 Cu(s)+ Al(NO3)3(aq) 2

4. Double displacement General: AB + CD  AD + CB Example: MgO + CaS 

Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq) Another example: K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s) 2

5. Combustion Reactions Combustion reactions - a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) Fuel (hydrocarbon) 2) Oxygen 3) Something to ignite the reaction (spark)

Combustion Reactions In general: CxHy + O2  CO2 + H2O Products are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C8H18)

Combustion Example C5H12 + O2  CO2 + H2O Write the products and balance the following combustion reaction: C10H22 + O2  8 5 6

Endothermic & Exothermic Change

Whenever chemical reactions occur, energy is transferred to or from the surroundings. An exothermic reaction is one which transfers heat energy to the surroundings An endothermic reaction is one which takes heat energy from the surroundings

Exothermic process: a physical or chemical change that releases heat energy reaction Exothermic Change - heat is given off and the temperature rises Burning fossil fuels is an exothermic reaction.

Reactants  Products + Energy as Heat

Exothermic Examples Chemical Change Physical Change A candle flame Rusting iron Burning sugar Glow sticks Fire crackers Physical Change Some hand warmers Some dissolving

Endothermic reaction - heat is taken in and the temperature may drop Endothermic process: a physical or chemical change that requires (or absorbs) heat energy reaction Endothermic reaction - heat is taken in and the temperature may drop Photosynthesis is an endothermic reaction (requires energy input from sun)

Reactants + Energy as Heat  Products

Endothermic Examples Chemical Change Physical Change Baking bread Cooking an egg Physical Change Sometimes dissolving Cold packs from nurse