7 Review SUGGESTED ANSWERS

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CHAPTER
7
Review
SUGGESTED ANSWERS
WHAT DO YOU REMEMBER?
1.
Chemical
name
Chemical
formula
Atom?
Y/N
Molecule?
Y/N
Element?
Y/N
Compound?
Y/N
Total number
of atoms
sulfur dioxide
SO2
N
Y
N
Y
3
chlorine
Cl2
N
Y
Y
N
2
hydrogen
peroxide
H2O2
N
Y
N
Y
4
Si
Y
N
Y
N
1
carbon dioxide
CO2
N
Y
N
Y
3
butane
C4H10
N
Y
N
Y
14
C27H46O
N
Y
N
Y
74
O3
N
Y
Y
N
3
silicon
cholesterol
trioxygen
2. (a) “Diatomic” refers to
(b) H2, O2, N2, F2, Cl2,
elements that exist under normal conditions as two-atom molecules.
Br2, I2
3. (a)
ionic; (b) ionic; (c) molecular
4. (a)
CO2; (b) H2; (c) O2
5.
A molecular element is composed of molecules that contain two or more atoms of only one element, whereas
a molecular compound is composed of molecules that contain atoms of two or more elements.
6.
Ionic compounds form when atoms lose or gain one or more electrons to form, respectively, positive
and negative ions that are attracted to one another due to their opposite charges.
7.
Non-metallic elements combine to form molecules.
8.
Metallic elements combine with non-metallic elements to form ionic compounds.
WHAT DO YOU UNDERSTAND?
9.
10.
FeO and Fe2O3.
The white crystals are a compound. Heating caused them to form a simpler substance, oxygen gas,
indicating that the white crystals are an oxygen-containing compound.
11. (a)
(b)
Sample answer: Dear Resident, This is to inform you that your food supply may contain high levels
of toxins. The cause of this contamination is that migratory animals eat prey and other food in far
ranging regions, some of which are polluted. These animals can then travel to relatively pristine regions
such as your own, carrying toxins in their tissues. Thank you.
The toxic chemicals that spread globally and that are amplified in the food chain are very stable and
do not break down in the environment.
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Chapter 7 Chemical Compounds
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SOLVE A PROBLEM
12.
Answers will vary. Students should state that eye protection, an apron and protective gloves must be worn. The
procedure would be to dissolve a small amount of the white powder in water and then to test the resulting
solution with a conductivity tester. If the white powder is glucose, the solution will not have better electrical
conductivity than pure water.
13.
Answers will vary. Students should state that eye protection, an apron, and protective gloves must be worn.
Sample answer: Chalk (as a mineral, a form of limestone; as a writing implement, the mineral gypsum) is not very
soluble in water, whereas icing sugar and baking soda are. If the powder dissolves in water, it is not chalk. If the
powder is found to be either sugar or baking soda, and strongly heating causes it to char, it is sugar.
14.
Sample answer: While wearing eye protection and an apron, put a sample of a carbonated beverage in
a test tube and insert a rubber stopper to which a rubber tubing is attached. Place the open end of the
rubber tubing in limewater. Shake the sealed beverage sample to release gas; if the gas bubbling through
the limewater turns it milky white, the gas is CO2.
CREATE AND EVALUATE
15. (a)
16.
The molecules of CH4 should have four “hydrogens” stuck to a single “carbon.” Each O2 molecule
should have two “oxygens” stuck together.
(b)
Students should find that they have one CO2 molecule with two “oxygens” stuck to one “carbon,” and
two H2O molecules, each with two “hydrogens” stuck to one “oxygen.”
(c)
If insufficient oxygen is present, the carbon in the fuel gas (such as methane or propane) will not be
fully converted to CO2, becoming CO instead.
An electric current can cause chemical changes, suggesting that passing electricity through water changes
the water into new substances that are likely simpler because they are gases. This shows that water is a
compound. Similarly, when hydrogen pops in the presence of a flaming splint, it has burned by combining
chemically with oxygen to form water. Thus water is a compound of hydrogen and oxygen.
REFLECT ON YOUR LEARNING
17.
Answers will vary. Students should realize that a vast number of living organisms depend on oxygen
to survive and even small changes in the oxygen level of the atmosphere could have huge effects on
ecosystems. Students may also realize that fires might not even ignite in a lower oxygen atmosphere or be
very hard to put out in a higher oxygen atmosphere.
18.
Answers will vary. Student responses should focus on how reusing products rather than quickly discarding
them reduces trash in landfills and also saves energy by reducing the manufacture of replacement products.
Similarly, if products must be discarded, using biodegradable materials reduces stress on the environment
caused by materials that remain intact for very long periods of time.
WEB CONNECTIONS
19.
In some areas, iodine is lacking in the diet, which can lead to a swelling of the thyroid gland, known as goiter. Since
about 1920, iodine has been promoted as an additive to commercial salt to cure or prevent goiter. In Canada,
legislation introduced in 1949 makes it mandatory for salt to be iodized unless the salt product is a specialty item.
20.
Major risks associated with body piercing include infection, allergic reaction to the metal piercing, nerve
damage, excessive bleeding, spread of disease through cross-contamination, and keloid scar tissue. The
questions to ask a body piercer should focus on what assurances he can provide that the equipment is
properly sterilized and that he has training and/or experience in the procedures.
21.
Nanoparticles do pose dangers. They have a high surface to volume ratio, which can make them reactive or
able to speed up other reactions greatly. Since they can pass through cell membranes in organisms readily,
they have the potential to affect or even disrupt normal biological processes. Research on such effects is still
in the early stages.
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Unit C: Atoms, Elements, and Compounds
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