Transcript 1 Types of Chemical Reactions

Since atoms and molecules are too
small to see chemical changes are
detected by the following observations:
A colour change occurs.
A new gas with different properties is
formed.
Sudden dramatic changes in
temperature occur.
A new solid suddenly appears.
Chemical Changes are represented by word
equations and chemical equations.
When propane gas burns in air it produces
carbon dioxide and water. The word equation
for this reaction is:
Reactants
Products
propane + oxygen => carbon dioxide + water
are consumed
are produced
The chemical equation is:
C3H8 + 5 O2 -----> 3 CO2 + 4 H2O
The balanced equation is:
Types of Chemical Reactions
 During chemical changes new
substances with different physical
and chemical properties are formed.
 Chemical reactions can be grouped
into categories depending on the
nature of the chemical reaction.
 For example during a decomposition
reaction a single substance can break
apart into several different
substances.
Decomposition
Notice the intact particle on the left
breaks apart into multiple particles on the
right.
Decomposition
Potassium
chlorate can be made to decompose using heat.
When it decomposes it forms potassium
chloride and oxygen gas.
2 KClO3
2 KCl
3 O2
Single Displacement
This type of reaction is similar to a single
person at a dance “butting” in and
stealing someone’s partner.
Single Displacement
If copper metal is placed in a solution of silver
nitrate the silver will replace the copper.
Cu + 2AgNO3
2Ag
Cu(NO3)2
See chapter 4, lesson 16 , Saunders Interactive Chemistry
Double Displacement
guy girl
guy
girl
This type of reaction is similar
to a partner “swap”.
Remember only guy - girl
pairings.
Double Displacement
If potassium iodide is placed in a solution of
lead(II) nitrate the products are
Potassium nitrate and lead(II) iodide
PbI2
2 KNO3
2 KI + Pb(NO3)2
See chapter 4, lesson 16 , Saunders Interactive Chemistry
Synthesis
When 2 or more substances combine to
form a substance with larger molecules it
is called a synthesis.
Proteins are synthesized from 20
different amino acids.
Synthesis
If hydrogen gas is burned in the presence of
oxygen gas water vapour is synthesized.
2 H2 + O2
2 H2O
Combustion Reactions occur when fuels
are combined with oxygen. The products
are water vapour and carbon dioxide if it
is a complete combustion.
Incomplete combustions produce carbon
monoxide and water and/or carbon and
water.
Here is an example of a complete
combustion:
butane + oxygen
C4H10 +13O2
2
carbon
+
water
dioxide
4CO2 + 5 H2O