Chemical Reactions AVHS – Chemistry

How do you know a Chemical reaction has taken place? Here are the 10 ways that you can tell if a chemical change (reaction) has taken place. 1.Bubbles of Gas 2.Precipitate Forms 3.Color Change Occurs 4.The Temperature Changes

5. Light is Emitted 6. A Change in Mass or Volume occurs. 7. A Change in Conductivity occurs. 8. A Change in Melting/Boiling Point occurs. 9. A Change in Taste or Smell. 10. A Change in any Distinctive Chemical or Physical Property.

Chemical Equations Reactants are the chemicals listed on the left hand side of a chemical equation. Products are the chemicals listed on the right hand side of a chemical equation. A + B  AB

Types of Reactions Combination (Synthesis) Reactions Decomposition Reactions Displacement Reactions Double Displacement Reactions Combustion Reactions (a specific Synthesis reaction)

Synthesis Synthesis Reactions build a compound from simpler compounds or elements. General form: A + B -> C Recognition: Usually a single product and several reactants Synonyms: synthesis Examples C 2 H 4 (g) + H 2 O(g) C 2 H 5 OH(g) H 2 (g) + ½ O 2 (g) H 2 O(l)

Decomposition Decomposition reactions break a compound into simpler fragments. 4 H 2 O 2 4 H 2 O + 2 O 2 General form: C -> A + B Recognition: Usually a single reactant and several products Examples H 2 CO 3 (aq) H 2 O(l) + CO 2 (g) CaCO 3 (s) CaO(s) + CO 2 (g)

Displacement Displacement reactions involve replacement or swapping of parts of a compound. General forms single displacement: A + BC AB + C double displacement: AB + CD AD + BC Features # of reactants is usually equal to the # of products atoms or ions migrate from one compound to another Examples Zn(s) + 2 HCl(aq) ZnCl 2 (aq) + H 2 (g) Mg(s) + CuCl 2 (aq) MgCl 2 (aq) + Cu(s)

Combustion A type of synthesis reaction. Combustion reactions always involve molecular oxygen O2. Anytime anything burns (in the usual sense), it is a combustion reaction. Combustion reactions are almost always exothermic (i.e., they give off heat) Examples C x H y + O 2 --> CO 2 + H 2 O