Chemical Reactions Chemical Reaction: The conversion of old material into new material via a chemical change. The Basic form for all chemical equations is: Old Stuff New Stuff Read the above line like this: “The old stuff reacts to form the new stuff.” “The old stuff yields the new stuff.” “The new stuff is produced from the old stuff.”

Chemical Equations, cont… Technical Terms Old Stuff = reactants (cuz they’re what’s reacting) New Stuff = products (cuz they’re what’s being produced) Reactants Products

Chemical Equations, cont…. Ex: Hydrogen peroxide reacts to form water and oxygen. Convert names to formulas & write equation. Hydrogen peroxide = H2O2 Water = H2O Oxygen = O2 Chemical Equation = H2O2 H2O + O2

Chemical Equations, cont… Four abbreviations are used to indicate physical states of chemicals: also shown as part of the chemical equation (s) = solid (l) = liquid (g) = gas (aq) = aqueous solution (=dissolved in water)

Chemical Reactions, cont… Key Point: There is no way that you can predict the physical states of materials. This is only done through observation. There is no pattern to the physical states in a reaction. A solid can give a solid, liquid, gas, or aqueous material. *This is why we cannot predict the physical states of materials.

How can we predict whether a reaction will occur? What are the driving forces that drive reactants toward products? 1. Formation of a solid (Precipitate) 2. Formation of water (Acid/Base rxns) 3. Transfer of electrons (oxidation/reduction rxns) 4. Formation of a gas (combustion)

You can count them on one hand! Chemical Reactions There are four (5) types of chemical reactions. You can count them on one hand!

2. Decomposition 3. Single Replacement 1. Combination or Synthesis 4. Double Replacement 5. Combustion Here we have it in of our hand

1. Combination/Synthesis Two or more reactants form one product A + B AB 2Na(s) + Cl2 2NaCl

2. Decomposition Reactions One reactant forms two or more products AB A + B 2H202 2H20(l) + O2(g)

3. Single Replacement Reactions An element reacts with a compound to form a new element and a new compound. AB + C AC + B The “C” replaced the “B” 2Na(s) + 2H20 2 NaOH(aq) + H2

4. Double Replacement Reactions Two Compounds react and produce 2 new compounds. AB + CD AD+ CB FeS(s) + 2HCl(aq) H2S(g) + FeCl2(aq)

Combustion A material reacts with oxygen to form a variety of compounds. AB + O2 misc. products 4Al(s) + 3O2(g) 2Al2O3 C3H8(g) + 5O2(g) 3CO2(g) + 4H20(g)

Match the type of reaction with the phrase. Double replacement Combustion 3. Decomposition 4. Single replacement 5. Combination A single reactant Two ionic compounds Oxygen and a substance A single product An element and a compound

Predicting Products of a chemical reaction. You have to be able to recognize the type of reaction and what should result. Look at the table on p.197 for general patterns.

Balance the following equations and identify the type of equation. Hf + N2 Hf3N4 Mg + H2SO4 MgSO4 + H2 Pb(NO3)2 PbO + NO2 + O2 Do the rest of the practice problems on p. 198.