 Two species combine to create one  Often, you will see two elements reacting to make a compound Ex: 2Na + Cl 2  2 NaCl

1. Metal Oxides and Water ◦ Produces a metal hydroxide compound (basic) ◦ Ex: Na 2 O + H 2 O  2 NaOH 2. Non-metal Oxides and Water ◦ Produces a solution that is acidic ◦ Acid Precipitation ◦ Ex: SO 2 + H 2 O  H 2 SO 3

 One species breaks down into at least two different species  Often, this will be a compound breaking down into elements Ex: 2 H 2 O  2H 2 + O 2

1. Bicarbonates (hydrogen carbonates) ◦ Carbon dioxide gas is formed ◦ Other products: carbonate and water vapour ◦ Ex: 2 KHCO 3  K 2 CO 3 + H 2 O + CO 2 2. Carbonates ◦ Under extreme heating conditions ◦ Produces an oxide and carbon dioxide gas ◦ Ex: K 2 CO 3  K 2 O + CO 2

4. Nitrates ◦ When a metal nitrate decomposes, it forms a metal nitrite and oxygen gas ◦ Ex: 2 KNO 3  2 KNO 2 + O 2 5. Hydroxides ◦ When a metal hydoxide decomposes, it forms a metal oxide and water ◦ Ex: Mg(OH) 2  MgO + H 2 O

 There are more complex decompositions…  Video Video

 An element or compound is reacting with oxygen, accompanied by a release of energy as heat or light  Products will always include an oxide  Hydrocarbons: made of carbon and hydrogen ◦ Ex: propane (C 3 H 8 ), gasoline, methane (CH 4 )…

 Complete Combustion: efficient combustion with ample amounts of oxygen ◦ Flames are blue, indicating a higher temperature ◦ Products: Carbon dioxide and water ◦ Ex: CH O 2  CO 2 + 2H 2 O

 Incomplete combustion: combustion when there is not enough oxygen ◦ Flames are orange, indicating a “cooler” temperature ◦ Products are varied: can include carbon (soot) and carbon monoxide (which are both pollutants), plus carbon dioxide and water ◦ Ex: 2 C 3 H 8 + 7O 2  2C + 2CO + 2CO H 2 O

 When other chemicals undergo combustion, other oxides are created ◦ Ex: NO 2 and SO 3 (non-metal oxides react with water - dangerous for the environment)  Combustion of Hydrogen gas - OWvk OWvk

 P. 121 # 4, 5, 7  Worksheet