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.

Element1 + 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 Element1 + 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.

S8(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 - alcohol isopropyl alcohol – rubbing alcolhol

Sodium bicarbonate – baking soda ethylene glycol - antifreeze

Methane – natural gas sodium chloride - salt

Dihydrogen oxide - water sucrose - 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 (1743-1794)

vinegar + baking soda sodium acetate + water + carbon dioxide gas

CH3COOH(aq) + NaHCO3(s) NaC2H3O2(l) + H2O(l) + CO2(g)