UNIT
C
Review
SUGGESTED ANSWERS
WHAT DO YOU REMEMBER?
1.
c
2.
a
3.
b
4.
c
5.
c
6.
c
7.
b
8.
b
9.
d
10.
d
11.
c
12.
d
13.
True
14.
False. In a neutral atom, the number of electrons equals the number of protons.
15.
False. The lustre of a substance is its shininess or dullness.
16.
False. In a chemical change, a new substance is produced.
17.
True
18.
False. Metals are lustrous, ductile, and malleable.
19.
True
20.
False. Compounds can be broken down into simpler substances.
21.
False. To determine the number of neutrons, subtract the atomic number from the mass number.
22.
False. In Bohr’s atomic model, the first electron orbit holds a maximum of 2 electrons.
23.
True
24.
True
25.
True
26.
mass
27.
density
28.
Workplace Hazardous Materials Information System.
29.
wafting
30.
physical
31.
chemical
32.
oxygen
33.
vinegar
34.
is table salt
35.
J. J. Thomson
36.
sulfur
37.
decomposition
38.
hydrogen
NEL
55219_04_ch07_p379-438_pp4.indd 431
Unit C Review
431
12/3/09 3:37:42 PM
39.
limewater
40. (a)
(iv); (b) (vii); (c) (i); (d) (viii); (e) (ii); (f) (iii); (g) (v); (h) (vi)
41. (a)
(iii); (b) (iv); (c) (i); (d) (ii)
42. (a)
(ii); (b) (iii); (c) (iv); (d) (v); (e) (i)
43.
Sample answer: The batter has changed colour, holes in the cake indicate that bubbles of gas formed, and a
mixture that was runny at room temperature is now solid at room temperature.
44. (a)
(b)
(c)
(d)
(e)
(f)
(g)
45.
46.
Physical change. The droplets form due to condensation and changes of state do not produce new
substances.
Physical change. The grinding changes the form of the wheat, but not the chemical identity of its
constituents.
Chemical change. The sugar chars (forms carbon); the change of colour indicates a chemical change.
Physical change. None of the ingredients of the peanut butter, jelly, or bread undergo a change of
chemical identity.
Chemical change. The production of heat indicates a chemical change.
Physical change. Neither the sugar nor the tea undergoes a change of chemical identity.
Physical change. The pieces of egg are made smaller and smaller, but do not undergo a change of
chemical identity.
Formula
Element
Compound
Atom
Molecule
H2O2
No
Yes
No
Yes
Fe
Yes
No
Yes
No
N2
Yes
No
No
Yes
CH4
No
Yes
No
Yes
O3
Yes
No
No
Yes
Element
name
Element
symbol
Atomic
number
Mass
number
Number of
protons
Number of
neutrons
Number of
electrons
potassium
K
19
39
19
20
19
tin
Sn
50
119
50
69
50
calcium
Ca
20
40
20
20
20
silicon
Si
14
28
14
14
14
fluorine
F
9
19
9
10
9
WHAT DO YOU UNDERSTAND?
47.
Students diagrams will vary, but should reflect the following: Matter can be classified into two categories:
mixtures and pure substances. Mixtures can be further categorized as solutions or mechanical mixtures.
48.
Alloys are mixtures of metals; the individual metals in alloys do not chemically combine.
49.
Sample answer: Two elements found in most kitchens are aluminum and copper; two compounds found
in kitchens are table salt (NaCl) and drain cleaner (sodium hydroxide); two mechanical mixtures found in
kitchens breakfast cereals and granola bars.
50. (a)
432
Air is a solution made up primarily of nitrogen, oxygen, and carbon dioxide
(b)
Salt water is an example of a solution formed by a solid dissolving in a liquid.
(c)
Clear apple juice is an example of a liquid solution.
Unit C: Atoms, Elements, and Compounds
55219_04_ch07_p379-438_pp4.indd 432
NEL
12/3/09 3:37:43 PM
51. (a)
52.
Quantitative properties give numerical information about a substance; qualitative properties do not
provide numerical information.
(b)
Colour and texture are qualitative properties; temperature and mass are quantitative properties.
(c)
Optical clarity can be described qualitatively with words, such as transparent, translucent, or opaque, it
can also be described quantitatively by expressing the percentage of light that passes through an object.
Compound
Types of Elements (metal/non-metal)
Type of Compound
NaCL
metal and non-metal
ionic
CO2
non-metals
molecular
KF
metal and non-metal
ionic
SO2
non-metals
covalent
CaO
metal and non-metal
ionic
53.
This definition is incomplete, because some matter cannot be seen or touched.
54.
The mass number is always equal to or greater than the atomic number. The mass number includes both
protons and neutrons, whereas the atomic number only includes protons.
55.
(a)
(b)
18pⴙ
22n0
(c)
15pⴙ
16n0
1pⴙ
0n0
56.
The new element should have a relatively low melting point, density, and hardness, but good electrical and
thermal conductivity as well as a shiny lustre when freshly cut or polished. It should have only one electron
in its outermost orbit, and should react with water.
57.
All of the elements in the alkaline earth metals have two electrons in their outermost orbit. Each element, however,
has a different number of orbits. Beryllium, for example, has two orbits, whereas magnesium has three orbits.
58.
In the second period, all of the elements have two orbits for electrons. Each element, though, has a
different number of electrons in the second orbit. Boron, for example, has three electrons in its second
orbit, whereas carbon has four.
59.
There are more metals. Many more elements lie to the left of the line that separates metals from non-metals.
60. (a)
61.
The fact that ice is less dense than liquid water is unusual, because for most substances, the solid form
is more dense than the liquid state.
(b)
If ice sank to the bottom of ponds in winter, the pond water would freeze from the bottom up,
trapping fish and other organisms in solid ice, likely killing them.
(c)
When liquid water turns to ice, the molecules spread out somewhat, making the density lower, and
the ice floats like the iceberg that sank the Titanic. If water freezes in cottage pipes or glass bottles, it
expands with such force that it can break the pipes or bottles.
Each of these processes is a chemical change involving, in part, oxygen atoms. Reactive oxygen atoms
in hydrogen peroxide can lighten the colour of materials; oxygen atoms combining with hydrogen and
carbon atoms cause combustion; and oxygen atoms combining with iron atoms cause rusting. The rate
at which these reactions occurs differs. Rusting is a slow reactions, bleaching is somewhat quicker, and
burning is a very quick reaction.
NEL
55219_04_ch07_p379-438_pp4.indd 433
Unit C Review
433
12/3/09 3:37:43 PM
62. (a)
Check that students have correctly rolled their cylinders. Model for students if necessary. Have
students place their finger on hydrogen, and then trace the elements by increasing atomic number.
(b)
The elements naturally flow from one to the next, so in some ways a cylinder is more logical, and a
spiral might be even more logical than a cylinder.
(c)
Elements’ properties change gradually except when going from a noble gas to an alkali metal, at which
point properties suddenly jump to much higher or lower values. In a cylinder periodic table, putting
the alkali metals right next to the noble gases does not suggest that properties will jump, which is less
logical than the regular periodic table.
63.
Bohr-Rutherford diagrams of potassium and chlorine:
19pⴙ
20n0
K
17pⴙ
18n0
Cl
(a)
Chlorine can gain one more electron to fill its outer orbit and have an electron arrangement like that
of argon. Potassium has one electron in its outermost orbit; by giving this electron away, its electrons
will be arranged like those in argon.
(b)
If a potassium atom collides with a chlorine atom, the potassium’s lone outer electron can be
transferred to the chlorine atom to make each atom have an electron arrangement like argon and thus
be stable. The potassium atom becomes a 11 ion and the chlorine atom becomes a -1 ion and their
opposite charges hold them together to form an ionic compound.
SOLVE A PROBLEM
64. (a)
Sample answer: To determine if a substance is a metal, I would check the following: I would check to
see if it is shiny (metals are shiny). I would check to see that it conducts electricity. I would also check
to see if it is malleable.
(b)
Sample answer: To determine the element’s identity, I would determine its mass and volume by
measuring. I would then use this information to calculate the sample’s density. Density is a characteristic
property; I can use this to determine the specific element.
65.
The information that silver and gold are found in pure form leads me to believe that they are not very
reactive; a more reactive substance would react with other substances and not be found in pure form.
66. (a)
(b)
The density of the wood before and after cutting stays the same,
This could be tested by measuring the mass and volume of wood before cutting and then the mass and
volume of a piece of wood after cutting. Using the mass and volume; the densities can be compared.
67.
Halogen lamps generally have a smaller quartz bulb inside an outer glass envelope. There is a small amount
of bromine or iodine inside the quartz bulb, so care should be taken not to break it during disposal, thus
releasing the halogen (although the amount is not really dangerous). The bigger problem is that some
halogen lamps have lead solder and, if so, must be treated as hazardous waste.
68.
Coal that is burned in power plants and boilers is a major source of mercury pollution. Waste incinerators
also produce mercury from mercury-containing products in the waste. Internationally, industry also
continues to cause mercury pollution. Using less energy, supporting the use of low-mercury coal and
accepting the cost of cleaning coal are ways to help mercury pollution. Mercury accumulates in living
things and is very toxic, attacking the central nervous system and other tissues.
434
Unit C: Atoms, Elements, and Compounds
55219_04_ch07_p379-438_pp4.indd 434
NEL
12/3/09 3:37:44 PM
CREATE AND EVALUATE
69. (a)
70.
Answers will vary, but should focus on major safety rules such as wearing goggles, gloves, and aprons,
following instructions carefully, and alerting the instructor when spills happen.
(b)
Answers will depend on the layout of the classroom.
(c)
Students’ explanations and drawings should match what is shown in Figure 2 on page 601 of the
Student Book.
The first discoveries that showed atoms had smaller particles inside could not have happened without
the invention of cathode ray tubes, an example of technology leading to improvements in atomic theory.
Better theories can also lead to better technology. For example, our understanding of how electrons behave
in atoms allows us to design molecules on computers for a specific purpose, thus avoiding many trial and
error experiments.
71. Mining in Northern Ontario
Benefits
Stresses
Creates jobs
Environmental pollution
Stimulates local economy
Directly harm to people
72. (a)
73.
ductility
(b)
To demonstrate malleability, one could hammer a piece of solder and show that it can be pounded flat
without breaking or shearing. To demonstrate electrical conductivity, one could include a length of
solder in a simple circuit of a small light bulb connected to a battery.
(c)
Both tin and bismuth have relatively low melting points as pure metals, which is reflected to a degree
in the very low melting point of the solder they form. In 10 kt gold jewelry, the colour of the gold may
still be somewhat visible, although other metals in the alloy can greatly influence the colour as well.
(d)
In sodium chloride, the properties of the sodium and chlorine are very different than when they
are pure elements. You can eat table salt, but pure sodium would explode in your mouth and pure
chlorine would poison you.
Review students’ logs to look for correctly identified examples of compounds and mixtures used in the art
project. Remind students that their artwork should relate to the information presented in the unit.
74. (a)
Solid B is most likely a compound because it decomposed into a gas and a powder.
(b)
Solid A is most likely an element because it simply changed state.
(c)
A physical test that could be done would be to continue heating the liquid and observe the boiling
point.
75. (a)
A chemical test that could be used to test which gas is oxygen is the burning splint test. If the gas is
oxygen a burning splint will burn more vigorously. If the gas is hydrogen, there will be a popping
sound.
(b)
76.
It is impossible for one of the gases to be carbon dioxide because carbon atoms are not present in
water.
The eagle will likely have the most toxins in its tissues because toxins do not break down and thus
bioamplify as you move up the food chain.
REFLECT ON YOUR LEARNING
77.
Sample answer: The periodic table is amazing because such a simple organization of the elements
summarizes a very large number of patterns in their properties.
78.
Sample answer: The periodic table is difficult to use because the patterns are not perfect.
NEL
55219_04_ch07_p379-438_pp4.indd 435
Unit C Review
435
12/3/09 3:37:44 PM
79.
Sample answers include using “billiard ball,” “plum pudding,” and “solar system” to describe atoms and
using “quark” to describe particles inside of protons and neutrons (Murray Gell-Mann named these
particles quarks after a line from Finnegan’s Wake by James Joyce: “Three quarks for Muster Mark!”).
80.
Sample answer: I would want my favourite sweater to be durable, so I could wear it many times over a
long time period. However, this would be a problem when I was done with the sweater, because it would
not break down in the landfill.
81.
Sample answer: Chemistry is called the central science, because all particles, matter and their interactions
are central to the workings of all areas of science.
82.
Sample answer: Understanding the properties of matter helps me make consumer decisions that are good
for the environment. I also can study matter to understand environmental issues such as pollution.
WEB CONNECTIONS
83. (a)
(b)
Water is very stable, so when hydrogen and oxygen combine to form water, a great deal of energy is
released, making them a good fuel.
The main safety problem with hydrogen is its flammability. It ignites so easily that it must be kept
away from sparks, hot objects and open flames. Leaking tanks are especially dangerous because
hydrogen fully mixed with air can be explosive!
84.
Answers will vary depending on the natural substance chosen by each student. Teacher should check the
following: each students has chosen a naturally occurring compound to research; students has identified
how the substance harms the environment or human health; students identifies at least one way the effects
of the substance can be controlled.
85.
Answers will vary. Students should examine the issue of the spread of pesticides through the food chain,
including toxic materials being carried far from their sources by migrating animals.
436
Unit C: Atoms, Elements, and Compounds
55219_04_ch07_p379-438_pp4.indd 436
NEL
12/3/09 3:37:44 PM