Chapter 6.1
Chemical Reactions
 A reaction happens when two or more molecules
interact and the molecules change and a new chemical
is produced. That's it. What molecules are they? How
do they interact? What happens? The possibilities are
infinite.
 When you are trying to understand reactions, imagine
that you are working with the atoms. Imagine the
building blocks are right in front of you on the table,
instead of billions of reactions in your beaker.
How do we know a chemical
reaction has taken place?
1.
2.
3.
4.
5.
6.
7.
A new colour appears
Heat or light is given off, change in temp
Bubbles of gas are formed
A solid(precipitate) forms in a liquid
The change is difficult to reverse
A change in odour
A new chemical has been formed
How can you describe the range of
reactions?
 Using word equations are a convenient way for chemists
to understand these reactions.
 A word equation is one way of representing a chemical
reaction.
 It tells you what reacts and what is produced.
 This is an efficient way to describe chemical changes, to
help chemists recognize patterns, and to predict the
products of a chemical reaction.
Why do we use word equations?
 “When the grey metal magnesium was picked up with
a pair of tongs and heated in the working flame of the
Bunsen burner a chemical reaction occurred. A
reaction with the oxygen caused a bright white light to
be produced and a crumbly white solid called
magnesium oxide was formed.”
 Being descriptive is important to know what actually
happened but it is often very time consuming. This
works better:
 Magnesium + Oxygen
Magnesium Oxide
 Word equations are written in a certain format.
 Names of what is reacting
Names of what is produced
( reactants )
( products )
 Multiple reactants and products are separated by plus (+)
signs and the arrows show the change from before the
reaction to after the reaction.
 Reactant 1 + Reactant 2
product 1 + product 2
EXAMPLES
 Wood + Spark
 Fabric + thread + buttons
Fire + smoke + heat
shirt
 The iron in a car reacts with oxygen to produce iron
(III) oxide, what we call rust.
 Iron + oxygen
iron(III) oxide
EXAMPLES
 We can also change this word equation into formula
equation. ( skeleton equation )
 Fe + O2
Fe2O3
TRY THIS
 Write a word and formula equation for the following:
 1) Zinc is added to hydrogen monochloride and this
produces hydrogen gas and zinc chloride.
 Answer:
 Zinc + hydrogen monochloride
 Zn + HCl
hydrogen gas + zinc chloride
H2 + ZnCl2
TRY THIS
 2) Sodium reacts with calcium bromide to make
calcium and sodium bromide
 Answer:
 Sodium + calcium bromide
 Na + CaBr2
Ca + NaBr
calcium + sodium bromide
TRY THIS
 3) Carbon dioxide and water are produced when
methane is added to oxygen.
 Answer:
 Methane + oxygen
 CH4 + O2
carbon dioxide + water
CO2 + H2O
Class Work
 Complete 6.1 & 6.5 Chemical Equations Worksheet
 *do not attempt to balance the equation as we will
cover that tomorrow.
HOMEWORK
 DO QUESTIONS 2 AND 3 ON PAGE 219