Chemical Reactions A chemical change is any change in which a new substance is formed. Evidence: Release of energy as heat and light, change in colour, formation of gas, change in odour, etc. Examples: sulfur + oxygen  sulfur dioxide phosphorus + oxygen  diphosphorus pentoxide magnesium + oxygen  magnesium oxide iron + oxygen  iron(III) oxide

Types of Chemical Reactions combustion: AB + oxygen  oxides of A & B synthesis: A + B  C decomposition: AB  A + B single displacement: A + BC  AC + B double displacement: AB + CD  AD + CB

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

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

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

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

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

Chemical Reactions combustion: AB + oxygen  oxides of A & B Example: 2C 8 H O 2  16CO H 2 O Combustion occurs when a carbon containing substance burns and creates CO 2 and H 2 O Cellular Respiration is a controlled combustion reaction: Glucose + Oxygen  Carbon dioxide + Water