Chemical Reactions

Chemical Reactions New Substances produced by changing the way atoms are arranged Physical Changes ≠ Chemical Reaction Evidence Change in Color (rust) Temperature Change (endo/exo-thermic) Formation of a Gas Formation of a Solid (Precipitate)

Chemical Equation Uses chemical formulas and symbols to describe a chemical reaction and the product it produces (see below) Symbol Meaning Produces or Yields (aq) Aqueous + Plus Heat Reactants heated (s) Solid Light Reactants exposed to light (l) Liquid Elec Electric current applied to reactants (g) Gas

Reactants: Substances Present @ Beginning Products: Substances Formed by the Reaction Yields: An “equal sign” in a chemical reaction meaning “produces”, “creates”, or “forms”… Na + Cl2  NaCl Reactants Yields Products

Reaction Classifications

A new compound is formed by combining simpler reactants Synthesis …Combining Elements… A new compound is formed by combining simpler reactants A + B  AB Mg + O2  MgO

Decomposition CD  C + D H2O  H2 + O2 …Separating Elements… A reactant breaks down into simpler products (opposite of synthesis) CD  C + D H2O  H2 + O2

…FIRE! (Needs Oxygen and produces CO2 )… Combustion …FIRE! (Needs Oxygen and produces CO2 )… EF + O2  H2O + CO2 CH4 + O2  H2O + CO2

Single Replacement …Switch out ONE element with another in a compound!... GH + I  GI + H CuCl2 + Zn  ZnCl2 + Cu

…Switch Out Two Elements with Two Others!... Double Replacement …Switch Out Two Elements with Two Others!... JK + LM  JM + KL AgNO3 + HCl  AgCl + HNO3

Rate of Reaction Concentration Surface Area Temperature High Concentration = faster reaction Surface Area More surfaces available to react = faster reaction Temperature Higher Temperatures = faster reaction Particles speed up or slow down…speeding up or slowing down the reaction…

Rate of Reaction (Cont’d) Catalyst Something that speeds up the rate of reaction without being affected itself. Inhibitor Something that slows down the rate of reaction without being affected itself. (Stop Here)

The Law of Conservation of Mass Matter Can Neither Be Created Nor Destroyed Reactants and Products MUST be EQUAL! So… We Balance Chemical Equations!

Videos! Alkali Metals in Water (3 min) Sodium in Water (1 min) Francium Bomb in Ocean (30 sec) Chemistry Explosions (13 min)