Chapter 3: Types of Chemical Reactions Unit A: Matter and Chemical Change

What we already know…  Chemical reactions can be simple or complex  Chemical changes can be obvious or less noticeable  Chemical reactions can occur immediately or more slowly To describe chemical reactions, we use word equations

3.1 Word Equations  Word equations are always written in the same format  Left side of the equation lists the reactants  Right side of the equation lists the products  Arrow points from the reactants to the products  All the reactants and all the products are separated by a plus sign (+) reactant 1 + reactant 2 product 1 + product 2 All ProductsAll Reactants

3.1 Word Equations Continued Oxygen + food (glucose) carbon dioxide + water + energy Carbonic acid and calcium carbonate produce calcium hydrogen carbonate

3.2 Types of Reactions  In a simple composition reaction, two or more simple elements combine to form a compound. Element 1 + Element 2 Compound A + B AB magnesium + oxygen magnesium oxide + light + thermal energy Most simple composition reactions are exothermic

3.2 Types of Reactions Continued  In a simple decomposition reaction, a reaction breaks a compound into its component elements. Compound Element 1 + Element 2 AB A + B water + electric energy hydrogen gas + oxygen gas Most decomposition reactions are endothermic

3.2 Types of Reactions Continued  Combustion reactions always occur in the presence of oxygen.  Candle wax burning in the presence of oxygen produces carbon dioxide and water  Neutralization reactions are an acid reacting with a base to produce a form of salt and water. acid + base salt + water

3.3 Formulas for Common Compounds sulfur + zinc zinc sulfide  A chemical name is the standard scientific name by which each element or compound is known; established by an internationally recognized naming system.  A chemical formula is the standard scientific symbol by which each chemical element or compound is known. S 8(s) + 8Zn (s) 8ZnS (s)

3.3 Formulas for Common Compounds Continued  Many chemical compounds are often identified by a common name.  Easier to use and have existed before the international naming system Ethanol - alcoholisopropyl alcohol – rubbing alcolhol Sodium bicarbonate – baking sodaethylene glycol - antifreeze Methane – natural gassodium chloride - salt Dihydrogen oxide - watersucrose - sugar

3.4 Chemical Equations  The Law of Conservation of Mass states: In a chemical reaction, matter is not created or destroyed. If you start a reaction with 10g of reactants, you will end up with 10g of products. ~ Antoine Lavoisier ( ) vinegar + baking soda sodium acetate + water + carbon dioxide gas CH 3 COOH (aq) + NaHCO 3(s) NaC 2 H 3 O 2(l) + H 2 O (l) + CO 2(g)