Science - SNC 2P
Unit 2: Chemistry
Activity 2: Types of Chemical Reactions
Overview
You will investigate chemical reactions encountered in everyday life and their practical applications.
You will describe, using your observations, the reactants and products of a variety of chemical
reactions, including synthesis, decomposition, and displacement reactions. You will apply WHMIS in
the safe handling and storage of chemicals. You will continue to develop laboratory skills and will be
required to report on a lab, including the chemical equations expressing what occurred.
Expectations
Overall Expectations:
CHV.02P investigate chemical reactions encountered in everyday life and their practical applications.
Specific Expectations:
CH1.03P describe, using their observations, the reactants and products of a variety of chemical
reactions, including synthesis, decomposition, and displacement reactions (e.g., the burning of
magnesium, the production of oxygen from hydrogen peroxide, the reaction of iron in copper
sulphate);
CH2.01P through investigations and applications of basic concepts select and use appropriate
apparatus, and apply WHMIS safety procedures for the handling, storage, disposal, and recycling of
laboratory materials (e.g., wear safety goggles and aprons; use proper techniques to handle, dispose
of, and recycle acids, bases, and heavy metal ions; describe procedures to be followed in an
emergency);
CH2.08P conduct experiments to determine the factors that affect the rate of a chemical reaction
(e.g., temperature, surface area of a solid, concentration of a solution);
CH2.09P represent simple chemical reactions using word equations, balanced chemical equations,
and, where appropriate, molecular models.
Content
We encounter thousands of chemical reactions every day. When we get up in the morning and have
breakfast, we are triggering the process of digestion. As we get into cars or onto buses, we need still
more chemical reactions to move us around. Our clothes are the result of chemical reactions, our
water bottles, pens, paper, binders, perfume and just about every thing else. Some reactions are
beneficial, some are harmful, and some are determined by the way in which we use them.
People who work with chemicals need to have a good idea of what is going to happen when
chemicals are mixed. If they didn’t, there would be many more accidents and explosions in labs. After
centuries of experience, scientists generally have a rough idea of what to expect, based on how a
substance reacts with other substances.
There are several standard types of reactions:
Synthesis Reactions occur when elements are joined to make compounds. These compounds can
be simple or complex. The starting substances are called reactants (because they react) and the end
results are called products (because they are produced). Raw materials are used to synthesize a
product.
Example
Hydrogen + oxygen = water
(word equation)
2H + O
(balanced chemical equation)
H2O
Decomposition Reactions are the opposite of Synthesis Reactions. They occur when a substance
is broken down, or decomposed.
Example
Lithium oxide = lithium and oxygen
Li2O
2Li + O
(word equation)
(balanced chemical equation)
Combustion Reactions occur when a substance is burned in oxygen. This causes the substance to
combine with oxygen. When metals are burned, they produce a metal oxide. When non-metals are
burned, they produce a dioxide.
Example
Sodium + oxygen = sodium oxide
Na + O
NaO
(word equation)
(balanced chemical equation)
Example
Carbon + oxygen = carbon dioxide
(word equation)
C + 2O
(balanced chemical equation)
CO2
Other types of reactions involve the displacement of one molecule or element with another.
Single Displacement reactions occur when one substance is displaced by another.
Example
fluorine + calcium bromide = calcium fluoride and bromine
2Fl + CaBr2
CaFl2 + 2Br
(word equation)
(balanced chemical equation)
The fluorine has displaced the bromine in the above reaction.
A Double Displacement Reaction occurs when the molecules of two substances switch places.
Example
Barium sulphide + potassium iodide = barium iodide + potassium sulphide
(word equation)
BaS + 2KI
BaI2 + K2S
(balanced chemical equation)
Did you know?
Have you ever wondered why substances like carbon dioxide and carbon monoxide are so
dangerous? They bond more easily with the iron in our red blood cells, and so will “displace” oxygen
in that reaction. So rather than our blood carrying oxygen to the cells, they are carrying carbon
monoxide. Our cells cannot use carbon monoxide, and need oxygen to survive. This can result in
brain damage and even death.
Check Your Understanding
1. What would balance the following equation?
Na + Cl2
NaCl
a. adding another Na
b. adding another NaCl
c. adding another Na and Cl2
d. adding another Na and NaCl
Answer
2. The following is a _______________ equation.
H2 + Cl2
2HCl
Answer
3. Is the following statement true or false?
In a double displacement reaction occurs when two compounds recombine to make two new
compounds.
Answer
Assignment
See Mrs. Viirre for handouts 