Chemical Reactions

A chemical change takes place when chlorophyll breaks down into a new substance. This is an example of a Chemical Reaction.

A chemical reaction is a process in which one or more substances change to make on or more new substances. The chemical and physical properties of the new substances differ from those of the original substances.

More examples: Baking of bread (yeast), metal rusting, burning of wood

Statements that indicate the reactants and products in a chemical reaction.

Ex. Iron (s) + chlorine (g) → iron (III) chloride (s)

This is read as:

“Solid iron and chlorine gas react (combine) to produce solid iron (III) chloride”

A skeleton equation uses chemical formulas rather than words to identify the reactants and products of a chemical reaction.

The word equation

Iron (s) + chlorine (g) → iron (III) chloride (s)

The skeleton equation

Fe(s) + Cl₂(g) → FeCl₃ (s)

A skeleton equation is not yet “balanced” by coefficients!

All involve oxygen (O2) as a reactant, combining with another substance

All combustion reactions are are exothermic

Complete combustion of a hydrocarbon always produces CO2 and H2O

Incomplete combustion of a hydrocarbon will produce CO and possibly C (black carbon soot) as well