Download Unit 3 Ch. 9 - Classifying Chemical Reactions

Lesson: Classifying Chemical Reactions
Field Museum Extensions
a. Related Exhibitions.
1. Evolving Planet. Chemical reactions are not simply found in the lab,
they occur all around us and shape the world in which we live. Visit the
Precambrian gallery of the Evolving Planet exhibition to see how…
The following chemical equation shows the reaction performed by the
bacteria. Write coefficients into the equation so it is properly balanced.
6 CO2 + 6 H2O + light energy 
C6H12O6 +
O2
(Answer: 6 CO2 + 6 H2O + light energy  1 C6H12O6 + 6 O2)
The oxygen produced by the photosynthetic bacteria caused two
important chemical transformations in the Earth. First, it oxidized the
element iron and turned it into rust. Write coefficients into the equation
below for the rusting of iron.
Fe +
O2  2 Fe2O3
(Answer: 4 Fe + 3 O2  2 Fe2O3)
The rusted iron particles created layers of colored sediment on the ocean
floors. Second, some of the oxygen in the atmosphere was converted
into ozone. Write coefficients into the equation below which shows this
conversion of one oxygen allotrope into the other.
O2 + ultraviolet radiation 
O3
(Answer: 3 O2 + ultraviolet radiation  2 O3)
2. What is an Animal?. At the west end of the exhibition, a display shows
the relative abundance of animals. Note that insects and mollusks, the
group that clams and snails, is the most abundant group. So why don’t
the skeletons and shells of dead insects and other creatures litter the
landscape and oceans? It’s decomposition!
Decomposition reactions occur when a compound decomposes, or splitsup, into two or more compounds and/or elements. For example
mercury(II) oxide will, upon heating, decompose into mercury metal and
oxygen when heated:
HgO  Hg + ½ O2
Since heat had to be added to make this reaction go, it is an endothermic
reaction. Most decomposition reactions are endothermic. Another example
of a decomposition reaction is the heating of calcium carbonate (the
material that makes up sea shells). Write coefficients into the equation
below which shows this conversion.
CaCO3  _ CaO + _ CO2
(Answer: CaCO3  1 CaO + 1 CO2)
3.
North American Indians: Find the “Origins aof Navaho Silver” display.
Note that the belt ornaments are slightly tarnished. What is tarnshing?!
When silver tarnishes, it combines with sulfur and forms silver sulfide
(Ag2S). Silver sulfide is black. When a thin coating of silver sulfide forms
on the surface of silver, it darkens the silver. The silver can be returned to
its former luster by removing the silver sulfide coating from the surface.
There are two ways to remove the coating of silver sulfide. One way is to
remove the silver sulfide from the surface. The other is to reverse the
chemical reaction and turn silver sulfide back into silver (Ag). Write
coefficients into the equation below which shows this conversion.
_ Ag2S + _ Al  _ Ag + Al2S3
(Answer: 3 Ag3S + 2 Al  6 Ag + Al2S3)
b. Harris Educational Loan Center Materials.
1. Video: Children of the River. See how students on a Native reservation
in Canada test water quality to ensure that chemical companies are not
polluting.