ist9_ch05.qxd
7/21/09
2:51 PM
Page 201
Home
Quit
CASE STUDY
B18
SKILLS YOU WILL USE
STSE Decision-Making Analysis
Skills References 4, 7
Heavy Metals in Fish
Evaluating reliability of data and
information
Using appropriate formats to
communicate results
Issue
Due to environmental pollution, the concentration of
heavy metals in fish is on the rise. For people who
eat a lot of fish, heavy metal contamination is a
serious concern.
Background Information
Many metals are necessary for human health. For
example, iron is so important in the diet that some
people need to take iron supplements. However, the
heavy metals, including cadmium, mercury, and
lead, are toxic.
Heavy metal pollution results mainly from
industrial processes, such as refining ores, burning
fuel, and using nuclear energy. Heavy metals are
also used in some types of batteries and computer
equipment. When these pollutants are released into
the air, they come back down with precipitation. In
this way, and from water washing over contaminated
landfills, heavy metals get into the water supply.
Once in the water, they build up in the food chain.
Fish near the top of the aquatic food chain often
contain high amounts of heavy metals. Therefore,
Health Canada and the government of Ontario have
set guidelines about how much of different types of
fish people should eat to avoid heavy metal
poisoning. Pregnant women in particular are
cautioned not to eat too much of certain types of
fish, as heavy metals can harm the fetus.
It is not always clear how much humans are
affected by heavy metals in their food. However,
scientists have seen an effect on contaminated
organisms. Fish stop functioning normally. They
seem to be unaware of their natural predators and
do not use their ingrained escape-and-evade
techniques. Heavy metal contamination also seems
to affect their sense of smell. Some fish have trouble
recognizing their own offspring, and instead of
protecting them, they eat them. This behaviour could
have a serious impact on the numbers of some types
of fish in the future — as well as the other organisms
in their environment.
Your task is to work with a partner find out who
may be at risk from heavy metals and why. Determine
what, if anything, the government should do to
protect people from this risk. Use a graphic organizer
to keep track of information. After you complete your
research, you will present your findings in a poster, an
interview, or another form of media.
Analyze and Evaluate
1. ScienceSource Gather information to help you
answer the questions below and complete your
overall task.
2. Why might Aboriginal peoples and people in
remote communities feel the effects of heavy
metal contamination of fish more than most
groups in Canada?
3. (a) What other cultures rely heavily on fish in
their diet?
(b) Should people from these cultures also have
concerns about heavy metal poisoning?
Explain.
4. What can be done to protect people from heavy
metal poisoning from their food?
5. Suppose you go fishing at a pond contaminated
with mercury and catch a minnow (a fish at the
bottom of the food chain) and a large trout (a
fish at the top of the food chain, which eats other
fish). Which fish would have a higher
concentration of mercury in its body? Why?
6. Create an informational poster, a question-andanswer interview that you and your partner can
share with the class, or another form of media,
giving the three best ways to protect people from
heavy metal poisoning.
Skill Practice
7. In your research, did a certain type of graphic
organizer seem more helpful than another? Why?
The periodic table organizes elements by patterns in properties and atomic structure.
201
ist9_ch05.qxd
7/21/09
2:51 PM
Page 202
Home
Quit
SKILLS YOU WILL USE
B19 Inquiry Activity
Skills References 2, 8, 9
Building a Periodic Table
Scientists use models to explain things we cannot see
or to display patterns in data.
Question
How can a model represent the patterns in the
periodic table?
Materials & Equipment
• 24 assorted nuts and bolts in a bag
• extra nut or bolt
• large sheets of paper
• ruler
• balance
• element cards
• graph paper
Procedure
Part 1 — Classifying Items Individually
1. Examine the 24 nuts and bolts from the bag
provided by your teacher.
2. Your bag originally contained 25 nuts and bolts,
but your teacher removed one of them. Identify
whether a nut or a bolt was removed, and
describe the missing piece in as much detail as
possible.
3. Share your classification ideas for the missing
object with another group. How were your ideas
similar? How were they different?
4. Revise your classification or description based on
your discussion.
5. Collect the missing nut or bolt from your teacher.
How close was your description to the missing
object? Revise your classification or description
based on this new information.
202
UNIT B
Atoms, Elements, and Compounds
Gathering, organizing, and
recording relevant data from
inquiries
Interpreting data/information to
identify patterns or relationships
Part 2 — Classifying Items Collectively
6. On a large sheet of paper, make a grid with five
equal-size columns and five equal-size rows.
Make sure the boxes are large enough to hold the
largest nut or bolt. Number the boxes 1 to 25,
starting on the top left at number 1 and working
across the row from left to right. The first box in
the second row should be number 6.
7. Place the smallest bolt at number 1 and the
largest nut at number 25, as shown below in
Figures 5.48 and 5.49. Now organize the rest of
the nuts and bolts on the grid.
1
smallest
bolt
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
largest
nut
Figure 5.48 Grid for organizing nuts and bolts
8. Follow your teacher’s instructions to measure
either the length and width or mass of each nut
and bolt. Record the measurements on your grid.
ist9_ch05.qxd
7/21/09
2:51 PM
Page 203
Home
B19 Inquiry Activity
Quit
(continued)
Part 3 — Classifying Elements
9. Collect an element card from your teacher.
10. Compare the properties on your card to those of
your classmates. Find classmates with cards that
have similar element properties. You will form a
group with these students.
16. Use your data on the elements from Part 3 to
make a graph of atomic mass versus atomic
number.
17. Record any patterns you notice in this graph.
18. Compare the two graphs you made. What
similarities do you see?
11. Make a list of the properties your group’s
elements all share. Share the list with your
teacher or class. Once your teacher confirms
your list, you will be given a group number.
19. Examine the periodic table on page 191.
Compare your arrangement of elements with the
arrangement of elements in the periodic table.
Describe their similarities and their differences.
12. Arrange all of your group’s element cards in order
of atomic mass.
Skill Practice
13. Make another five-by-five grid, as you did in
step 6. Complete it, using the order of the
elements in the class. Include the atomic mass
for each element in your grid. Write the element’s
group number at the top of the grid.
20. How many electrons do the following elements
have?
(a) carbon
(b) chlorine
(c) magnesium
(d) neon
Analyzing and Interpreting
14. Use your data from Part 2 to graph a nut or bolt
number versus nut or bolt size (length, width, or
mass). (The number of each nut or bolt is the
number of the box in the grid where the nut or
bolt was placed.)
Forming Conclusions
21. Return to the guiding question for this inquiry
activity. Examine the periodic table on page 191.
Based on your data and experiences, answer the
question.
15. Record any patterns you notice in this graph.
Figure 5.49 Arranging the nuts and bolts
Figure 5.50 The element cards
The periodic table organizes elements by patterns in properties and atomic structure.
203
ist9_ch05.qxd
7/21/09
2:51 PM
Page 204
Home
5.3
Quit
CHECK and REFLECT
10. Use the Bohr diagram below to answer the
questions that follow.
Key Concept Review
1. Refer to a periodic table to answer the
following questions.
(a) What is the chemical symbol for
sodium?
(b) What element has the symbol Hg?
Question 10
(c) What element sits directly below carbon
in the periodic table?
(d) Which element has atoms with a greater
mass: lithium or potassium?
2. Name four properties that Dmitri
Mendeleev used as criteria for organizing
the elements.
3. Name two groups on the periodic table that
include elements that conduct heat and
electricity.
4. What is the special name for Group 17 on
the periodic table?
5. Using hydrogen as an example, explain the
difference between atomic number and
atomic mass.
6. What happens to an atom if it loses a
valence electron?
7. Which of the following atoms typically
form negative ions?
(a) F
(b) Li
(c) Ne
(d) S
(e) Al
(a) What element is shown?
(b) How many electrons does this atom have?
(c) How many protons does this atom have?
(d) What group in the periodic table does
this element belong to?
11. In one of Dmitri Mendeleev’s first periodic
tables, he left two question marks between
zinc and arsenic.
(a) Why did he predict that eventually
someone would discover elements to fit
in the spaces he left in his periodic table?
(b) What were these two missing elements
named when they were later discovered?
12. Suppose a sample of a metal has a low
melting point and reacts easily with water.
What group does the element belong to?
13. Would the latest elements to be discovered
have heavier atoms or lighter atoms than
the other elements? Explain.
(f) Be
Reflection
Connect Your Understanding
8. If something occurs periodically — every
Monday, for instance — it can be said to
occur in a pattern. How do you think the
periodic table got its name?
14. How has your understanding of the term
“metals” changed since completing this
section? Write a definition for “metal,” and
list examples of metals with different
properties.
9. How do chemical symbols help scientists
from different countries communicate?
Why is this important?
15. List three ways that you can use the periodic
table in your studies that you did not know
about before completing this section.
For more questions, go to ScienceSource.
204
UNIT B
Atoms, Elements, and Compounds
ist9_ch05.qxd
7/21/09
2:51 PM
Page 205
Home
Quit
S C I E N Ceverywhere
E
Diamonds:
Responsible Mining
and Production
In the 1990s, geologists working in northern
Canada made an exciting discovery — several
diamond deposits! With the opening of the Ekati
diamond mine, 300 km northeast of Yellowknife,
Canada became a diamond-producing nation.
Canada soon became the world’s third-largest
producer of gemstone-quality diamonds, behind
only Botswana and Russia. For some remote
Aboriginal communities, the diamond mines in the
Northwest Territories and Nunavut have become
an important source of income. Shown here is the
Diavik diamond mine of the Northwest Territories.
This raw diamond must be processed before it can be used.
Diamond mining and processing raise some important ethical,
economical, and political issues. Diamond-processing facilities
produce waste heat and substances that can harm the environment.
Mines, too, have an environmental impact. Mines can interrupt the
path of migrating animals. Sometimes, lakes will be drained in order
to reach underwater diamond deposits. Aboriginal communities that
hunt or fish for food are concerned about the impact of the diamond
industry on the local environment.
Diamonds are valued as gems for their clarity and sparkle and
because they can be cut into detailed designs, as in the diamond
shown here. But diamonds have many other uses than as gems. The
hardest natural substance on Earth, diamond resists wear, chemical
change, and temperature extremes. Diamond is hard enough to cut
many types of rock and so is often used to make specialized saw
blades, drill bits, or grinding wheels. In medical and laboratory
equipment, thin, clear diamond membranes cover the openings
where laser beams or X-rays pass through.
The periodic table organizes elements by patterns in element properties and atomic structure.
205