Identify, give evidence for, predict products of, and classify the following types of chemical reactions: 1. Synthesis (combination) 2. Decomposition 3. Replacement 4. Combustion

 Synthesis  Decomposition  Replacement  Combustion

A chemical change: any change in which a new substance is formed. Evidence of a Chemical Change:  Release of energy as heat  Release of energy as light  Change in color  Formation of a gas  Change in odor…

1.Combustion: AB + oxygen  CO 2 + H 2 O 2.Synthesis: A + B  AB 3.Decomposition: AB  A + B 4.Single replacement: A + BC  AC + B 5.Double replacement: AB + CD  AD + CB

(c) McGraw Hill Ryerson 2007 –A + B  AB where A and B represent elements –The elements may form ionic compounds, like… –Sodium metal and chlorine gas combine to form sodium chloride. –2Na + Cl 2  2NaCl See pages Sodium added to chlorine gas Synthesis reactions are also known as FORMATION reactions. Two or more reactants (usually elements) join to form a compound.

Types: Synthesis Example C + O 2 OO C +  OO C OO C OO C O O C O O C O O C O O C O O C O O C O O C O O C O O C O O C O O C O O C General: A + B  AB

(c) McGraw Hill Ryerson 2007 Decomposition reactions are the opposite of synthesis reactions. –A compounds breaks down into two or more products (often elements). –AB  A + B where A and B represent elements 1. Ionic compounds may decompose to produce elements, like the following: Table salt, sodium chloride, can be broken down into sodium metal and chlorine gas by melting salt at 800ºC and running electricity through it. 2NaCl  2Na + Cl 2 See page 260

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

Types: Decomposition Example 2HgO  O Hg O OO + General: AB  A + B

(c) McGraw Hill Ryerson Covalent compounds may decompose into elements, like the following: By running electricity through water, the water molecules decompose into hydrogen and oxygen gases. 2H 2 O  2H 2 + O 2 DECOMPOSITION REACTION:

(c) McGraw Hill Ryerson 2007 Single replacement reactions replace one element from a compound with another element. –A compound and an element react, and the element switches places with part of the original compound. A + BC  B + AC A + BC  C + BA See page 261

Types: Single displacement Example: Zn + CuCl 2  Zn Cl Cu + General: AB + C  AC + B Cl Zn Cu +

(c) McGraw Hill Ryerson 2007 Double replacement reactions swap elements between 2 compounds that react together to form two new compounds. –Two compounds react, with elements switching places between the original compounds. AB + CD  AD + CB See page 262

Types: Double displacement Example: MgO + CaS General:AB + CD  AD + CB S O  Mg Ca + O S Mg Ca +

(c) McGraw Hill Ryerson 2007 –When potassium chromate and silver nitrate react, they form a red precipitate, silver chromate, in a solution of potassium nitrate. –K 2 CrO 4 + 2AgNO 3  Ag 2 CrO 4 + 2KNO 3 silver chromate Two solutions react to form a precipitate (solid) and another solution. Ionic solution + ionic solution  ionic solution + ionic solid. AB + CD  AD + CB

(c) McGraw Hill Ryerson 2007 Combustion reactions occur when a compound or element react with oxygen to release energy and produce an oxide. –Also sometimes referred to as hydrocarbon combustion. C X H Y + O 2  CO 2 + H 2 O where X and Y represent integers

(c) McGraw Hill Ryerson Natural gas (methane) is burned in furnaces to heat homes. »CH 4 + O 2  CO 2 + 2H 2 O + energy 2. An acetylene torch is used to weld metals together. »2C 2 H 2 + 5O 2  4CO 2 + 2H 2 O + energy 3. Carbohydrates like glucose combine with oxygen in our body to release energy. »C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy Acetylene torch