Case Study Explore an Issue · 2. A beginner’s telescope is usually priced at $350 or less. Most...
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12 Nelson Science 9 Nelson Science 9 13 Can elements in the periodic table occur in more than one form? Can an element be helpful in some situations and harmful in others? The answer to these questions is yes, and oxygen is an example of such an element. You will recall that oxygen exists in two different forms: oxygen gas and ozone. The colourless, odourless oxygen gas that we breathe has the formula O 2 . Without this gas, all organisms would die. Ozone is a pale blue gas with the chemical formula O 3 . It is formed by the action of sunlight on oxygen, by lightning, and as a side effect of pollutants released from car engines. At ground level, ozone is poisonous but, in the upper atmosphere, it protects us from the Sun’s radiation. Ozone and Sunlight You will remember that sunlight contains many different energies or colours of light, represented by the visible spectrum. Sunlight also contains invisible ultraviolet (UV) radiation, which has higher energy than any visible colour. UV radiation is believed to cause skin cancer, decrease the body’s resistance to diseases, and can blind unprotected eyes. It also harms plant life. Fortunately, less than 10% of the Sun’s UV radiation passes through the atmosphere. The reason is the ozone layer: ozone in the upper atmosphere that absorbs the UV radiation, preventing it from reaching the ground. The Ozone Killer Chlorofluorocarbons (CFCs) are compounds invented by chemists in the 1930s by putting together carbon, chlorine, and fluorine atoms. CFC’s seemed very safe because they were stable: they didn’t break down and they weren’t harmful to living things. CFCs were used to clean, to cool, and to dissolve other substances. The first CFC, Freon, is probably the coolant in your refrigerator at home. It took several decades for the first CFCs to work their way up through the atmosphere, where an unexpected reaction took place: UV radiation released chlorine atoms from the CFCs. And each chlorine atom broke apart 100 000 molecules of ozone. As the ozone broke down, the UV radiation was able to penetrate farther through the atmosphere, releasing more chlorine from CFCs as it went (Figure 1). An ozone killer was on the loose. Could it be stopped? The Montreal Protocol Recognizing the need to stop CFCs from reaching the ozone layer, over 100 countries signed the Montreal Protocol in September 1987, agreeing to cut CFC production in half by January 1996. Equipment that already contains CFCs was not banned for three reasons: the expense; the technology to completely replace CFCs is not yet developed; and the technology that depends on CFCs, Ozone: A Global Environmental Hazard 4.7 4.7 Explore an Issue UV radiation CFCs CFCs CFCs create ozone holes. UV rays penetrate ozone “hole.” Ozone layer blocks UV rays. ozone layer mesosphere stratosphere CFCs create ozone holes. UV rays penetrate ozone “hole.” Ozone layer blocks UV rays. Figure 1 120 Chapter 4 Benefits of a Ban Opinion of an atmospheric scientist If we ban CFCs, damage to the ozone layer may stop getting worse within a few decades. If we don’t, the ozone layer will keep getting thinner and thinner. Opinion of a dermatologist The sooner CFC use is ended, the less damage will be caused to people’s health. The rate of skin cancer may keep on climbing unless we do something now. Risks of a Ban Opinion of a consumer group If there is a total ban, all our fridges and air conditioners will have to be replaced. We can’t afford that. Besides, how do we know that the substitutes for CFCs are any safer? We used to think CFCs were safe. Opinion of a highrise owner Each of my apartment buildings has a large air conditioner. It would cost $200 000 to replace each one. I’d have to raise my rents. Opinion of a citizen It’s too late to worry about this. The CFCs are already up there. We can just wear sunglasses and use more sunblock. What Do You Think? • Should Canada ban CFCs totally? Should Canada stick to the Montreal Protocol? Is there another alternative? Research these questions. • Decide how you feel about this issue and assemble your thoughts and reasons into a position statement. Present your opinions in a letter to your member of parliament or to a local environmental group. Statement CFC production should be stopped completely by the end of this year. All refrigerators, air conditioning systems, manufacturing uses, etc., must be converted to allow the use of some other substance. Should CFCs Be Banned? The Periodic Table 121 especially the refrigeration of food and medicine, is too important to just shut it down. Some countries have still not agreed to the Montreal Protocol. Even in countries that are not producing CFCs, there is evidence that these chemicals are being smuggled in and used illegally. The production and use of CFCs remains a global issue. Figure 2 shows the use of CFCs by region. 50% refrigeration 13% solvents 5% other 32% blowing agents to make foam CFCs in Canada United States 29% Asia Pacific Rim 18% Canada 4% Western Europe 37% Eastern Europe 12% Figure 2 Use of CFCs by region. More than half of all CFCs used each year are released to the air. To prepare a persuasive report, you need to consider all factors related to the points you are trying to make. What factors do you need to consider for the challenge you have chosen? Research Skills SKILLS HANDBOOK: 3A Critical Thinking 3B 3A 3B Career Profile Each chapter highlights the career of a Canadian currently employed in a science and technology field. These features bring science to life, showing students that the information they are learning is being used by real people in real careers. Explore an Issue Explore an Issue is designed to present students with the opportunity to develop decision-making skills. Each unit has several Explore an Issue topics which allow students to synthesize their knowledge and skills by examining “real world” situations, researching further information, and justifying a position. M ary Lou Whitehorne is a stargazer who, within eight years, captured Canada’s highest award for an amateur astronomer—the Chant Medal. How did she do it, and why? As a Girl Guide in Bedford, Nova Scotia, Whitehorne was interested in the sky but, with no expert to talk to her and no local library, her interest waned. After high school, she graduated in medical laboratory technology and pathology, but left her medical career to raise a family with her husband, Lloyd. She went back to school, at age 31, to study at the Astronomy Department of St. Mary’s University. She undertook a three-year study of a rare type of star known as a B-emission star. “B-stars” vary in brightness, so she decided to investigate the light they emit. She spent many hours examining their spectra through a telescope to investigate their atomic composition. “It is challenging raising two kids while observing the stars every clear night past midnight,” she says, but she did it. She published two scientific papers, winning the 1993 Chant medal for her research efforts. She has since completed ground school and flight training as she works toward her Private Pilot Licence. She has also helped to establish a hands-on astronomy program for schools in Nova Scotia. In her spare time, she opened a resource centre for the Canadian Space Agency in the Atlantic region. Exploring 1. Find out if there are any introductory astronomy courses or programs in your area. Attend a stargazing party, if you can, and learn about the sky from an expert. 2. A beginner’s telescope is usually priced at $350 or less. Most astronomers will tell you that it is a big mistake to buy this type of instrument to explore the sky. Why? 3. Search the Internet for astronomical societies or amateur observing groups and write a brief summary of their activities. Prize-Winning Astronomer Sky-watching and the Solar System 431 Career Profile Career Profile ” “ It’s Terry Dickinson’s fault. In 1985, I saw a hokey little star chart in his newspaper column. In it, he said that you could see four moons of Jupiter all aligned on one side–with binoculars. That was all it took and I was hooked. Research Skills SKILLS HANDBOOK: 3A 3A Issue Students analyze, synthesize, and evaluate issues, and examine them from different perspectives or viewpoints. Case Study Case Studies introduce students to issues that, for reasons such as time, safety, or expense, they would not be able to investigate themselves. They are prompted to think about the technical aspects and social implications of the discoveries, as well as the actual observations. 482 Chapter 15 Figure 1 shows one of the most amazing images ever taken of outer space. It is called the Hubble Deep Field. When you look at it, you are peering back in time up to 8 billion years, into a part of the sky that appears no bigger than a grain of sand resting on a fingernail of your outstretched hand! Although this picture only shows you a tiny piece of the sky, it contains a lot of information. The only stars in the photograph are the objects that appear to have spikes. (This feature results from the wave nature of light.) All the other objects are galaxies. The Hubble Deep Field 15.6 15.6 Case Study Figure 1 This image was captured by the Hubble Space Telescope when it was aimed toward a part of the sky above the Northern Hemisphere. A photograph of the Hubble Space Telescope in orbit around Earth is featured on the first page of this unit. History of the Universe 483 (a) What can you infer about the number of galaxies in the universe? (In your answer, be sure to consider the concept of the “grain of sand” mentioned above.) (b)Which types of galaxies can you see? The image in Figure 1 was obtained by the Hubble Space Telescope over a period of about 100 h. It is similar to a time-lapse photo that might be taken here on Earth. (c) Why is time-lapse imaging important when viewing faraway galaxies? The “optical” portion of the Hubble Space Telescope includes a very large mirror, specially engineered with great precision. Unfortunately, there was an error in the manufacturing that was not detected until the telescope was launched: the curvature of the mirror was out by the thickness of a human hair, so it could not focus as well as had been hoped. Fortunately, astronauts were able to correct the problem in 1993 by adding a secondary mirror during a series of space walks. It was a delicate but successful operation. Other instruments have since been added to Hubble, improving its performance still further. (d)Why are more instruments added to the Hubble Space Telescope, instead of being put into orbit separately? What might be the advantages of each alternative? Advanced technology is needed to keep a telescope, travelling at almost 30 000 km/h while orbiting Earth, aimed steadily at one tiny spot for such a long time. (e) Why wouldn’t the telescope naturally stay pointed in the same direction? Make some predictions. This image sees deeper into space than any previous image. That is why it is called the “Hubble Deep Field.” The farthest objects, which are galaxies, are up to 8 billion light- years away. Galaxies 8 billion years ago had less structured shapes than galaxies now appear to have. This feature helps support the Big Bang theory. Understanding Concepts 1. How was the universe different 8 billion years ago than it is now? 2. Explain how this image allows scientists to “peer back in time.” Exploring 3. If you were responsible for aiming the Hubble Space Telescope to take a new Deep Field image, in which direction would you aim it? Give reasons. 4. Research the problems with Hubble’s mirror and how they were corrected. Draw a labelled diagram to explain the repairs. 5. Research the costs involved with the Hubble Space Telescope. Do you think it is a good use for the money? Explain reasons for your opinion in a brief letter to a science magazine. 6. Find out what other Deep Field images have been taken. View the images on a NASA web site. (f) Explain how the less structured shape of early galaxies supports the Big Bang theory. Astronomers observe evidence of several galaxies colliding with each other shortly after the Big Bang. (g) Propose a reason why galaxies in the past were more likely to collide than they are now. Studying such images in more detail will help scientists better predict what might happen to the universe in the future. (h)If you were a scientist studying images like this, what would you look for? Why? Research Skills SKILLS HANDBOOK: 3A 3A Challenge Connection Students are encouraged to consider how they might apply their knowledge and skills to complete the Challenge later in the unit. Skills Handbook Cross-References References indicate to students where they can find added information and extra help in the skills handbook for conducting investigations, activities, and answering questions.
Transcript of Case Study Explore an Issue · 2. A beginner’s telescope is usually priced at $350 or less. Most...
12 Nelson Science 9 Nelson Science 9 13
Can elements in the periodic table occur inmore than one form? Can an element behelpful in some situations and harmful inothers? The answer to these questions is yes,and oxygen is an example of such an element.
You will recall that oxygen exists in twodifferent forms: oxygen gas and ozone. Thecolourless, odourless oxygen gas that webreathe has the formula O2. Without this gas,all organisms would die. Ozone is a pale bluegas with the chemical formula O3. It is formedby the action of sunlight on oxygen, bylightning, and as a side effect of pollutantsreleased from car engines. At ground level,ozone is poisonous but, in the upperatmosphere, it protects us from the Sun’sradiation.
Ozone and Sunlight
You will remember that sunlight containsmany different energies or colours of light,represented by the visible spectrum. Sunlightalso contains invisible ultraviolet (UV)radiation, which has higher energy than anyvisible colour. UV radiation is believed tocause skin cancer, decrease the body’s resistanceto diseases, and can blind unprotected eyes. Italso harms plant life. Fortunately, less than10% of the Sun’s UV radiation passes throughthe atmosphere. The reason is the ozonelayer: ozone in the upper atmosphere thatabsorbs the UV radiation,preventing it fromreaching the ground.
The Ozone Killer
Chlorofluorocarbons (CFCs) arecompounds invented by chemists in the1930s by putting together carbon,chlorine, and fluorine atoms. CFC’sseemed very safe because they werestable: they didn’t break down and theyweren’t harmful to living things. CFCswere used to clean, to cool, and to
dissolve other substances. The first CFC, Freon,is probably the coolant in your refrigerator athome.
It took several decades for the first CFCs towork their way up through the atmosphere,where an unexpected reaction took place: UVradiation released chlorine atoms from theCFCs. And each chlorine atom broke apart100 000 molecules of ozone. As the ozonebroke down, the UV radiation was able topenetrate farther through the atmosphere,releasing more chlorine from CFCs as it went(Figure 1). An ozone killer was on the loose.Could it be stopped?
The Montreal Protocol
Recognizing the need to stop CFCs fromreaching the ozone layer, over 100 countriessigned the Montreal Protocol in September1987, agreeing to cut CFC production in halfby January 1996. Equipment that alreadycontains CFCs was not banned for threereasons: the expense; the technology tocompletely replace CFCs is not yet developed;and the technology that depends on CFCs,
Ozone: A Global Environmental Hazard
4.74.7 Explore an Issue
UV radiation
CFCsCFCs
CFCs create ozone holes.
UV rayspenetrate
ozone “hole.”
Ozonelayer blocks
UV rays.
ozone layermesosphere stratosphere
CFCs create ozone holes.
UV rayspenetrate
ozone “hole.”
Ozonelayer blocks
UV rays.
Figure 1
120 Chapter 4
Benefits of a Ban
Opinion of an atmospheric scientistIf we ban CFCs, damage to the ozone layermay stop getting worse within a fewdecades. If we don’t, the ozone layer willkeep getting thinner and thinner.
Opinion of a dermatologistThe sooner CFC use is ended, the lessdamage will be caused to people’s health.The rate of skin cancer may keep onclimbing unless we do something now.
Risks of a Ban
Opinion of a consumer groupIf there is a total ban, all our fridges and airconditioners will have to be replaced. Wecan’t afford that. Besides, how do we knowthat the substitutes for CFCs are any safer?We used to think CFCs were safe.
Opinion of a highrise ownerEach of my apartment buildings has a largeair conditioner. It would cost $200 000 toreplace each one. I’d have to raise my rents.
Opinion of a citizenIt’s too late to worry about this. The CFCsare already up there. We can just wearsunglasses and use more sunblock.
What Do You Think?
• Should Canada ban CFCs totally? Should Canada stick to the MontrealProtocol? Is there another alternative? Research these questions.
• Decide how you feel about this issue and assemble your thoughts andreasons into a position statement. Present your opinions in a letter toyour member of parliament or to a local environmental group.
Statement
CFC production should be stopped completely by the end of this year.All refrigerators, air conditioning systems, manufacturing uses, etc.,must be converted to allow the use of some other substance.
Should CFCs Be Banned?
The Periodic Table 121
especially the refrigeration offood and medicine, is tooimportant to just shut it down.
Some countries have stillnot agreed to the MontrealProtocol. Even in countriesthat are not producing CFCs,there is evidence that thesechemicals are being smuggledin and used illegally. Theproduction and use of CFCsremains a global issue.Figure 2 shows the use ofCFCs by region.
50% refrigeration
13% solvents 5% other
32% blowing agents to make foam
CFCs in Canada
United States 29%
Asia Pacific Rim 18%
Canada 4%
WesternEurope 37%
EasternEurope 12%
Figure 2
Use of CFCs by region. More than half of allCFCs used each year are released to the air.
To prepare a persuasivereport, you need toconsider all factorsrelated to the points youare trying to make. Whatfactors do you need toconsider for thechallenge you havechosen?
Research SkillsSKILLS HANDBOOK: 3A Critical Thinking3B
3A
3B
Career ProfileEach chapter highlights the career of a Canadian currentlyemployed in a science and technology field. These featuresbring science to life, showing students that the informationthey are learning is being used by real people in real careers.
Explore an IssueExplore an Issue is designed to present students with theopportunity to develop decision-making skills. Each unit hasseveral Explore an Issue topics which allow students to synthesizetheir knowledge and skills by examining “real world” situations,researching further information, and justifying a position.
Mary Lou Whitehorne is astargazer who, within eight years,captured Canada’s highest award
for an amateur astronomer—the ChantMedal. How did she do it, and why?
As a Girl Guide in Bedford,Nova Scotia, Whitehorne was interested in the sky but, with noexpert to talk to her and no local library, her interest waned.After high school, she graduated in medical laboratorytechnology and pathology, but left her medical career to raise afamily with her husband, Lloyd.
She went back to school, at age 31, to study at the AstronomyDepartment of St. Mary’s University. She undertook a three-yearstudy of a rare type of star known as a B-emission star. “B-stars”vary in brightness, so she decided to investigate the light theyemit. She spent many hours examining their spectra through atelescope to investigate their atomic composition. “It is challengingraising two kids while observing the stars every clear night pastmidnight,” she says, but she did it. She published two scientific papers,winning the 1993 Chant medal for her research efforts.
She has since completed ground school and flight training as sheworks toward her Private Pilot Licence. She has also helped to establisha hands-on astronomy program for schools in Nova Scotia. In her sparetime, she opened a resource centre for the Canadian Space Agency inthe Atlantic region.
Exploring
1. Find out if there are anyintroductory astronomy courses orprograms in your area. Attend astargazing party, if you can, andlearn about the sky from anexpert.
2. A beginner’s telescope is usuallypriced at $350 or less. Mostastronomers will tell you that it is abig mistake to buy this type ofinstrument to explore the sky.Why?
3. Search the Internet forastronomical societies or amateurobserving groups and write a briefsummary of their activities.
Prize-Winning Astronomer
Sky-watching and the Solar System 431
Career ProfileCareer Profile
”“It’s Terry Dickinson’s fault. In1985, I saw a hokey little star
chart in his newspaper column. Init, he said that you could see fourmoons of Jupiter all aligned onone side–with binoculars. That
was all it took and I was hooked.
Research SkillsSKILLS HANDBOOK: 3A
3A
Issue
Students analyze, synthesize,and evaluate issues, andexamine them from differentperspectives or viewpoints.
Case StudyCase Studies introduce students to issues that, for reasons such as time,safety, or expense, they would not be able to investigate themselves.They are prompted to think about the technical aspects and socialimplications of the discoveries, as well as the actual observations.
482 Chapter 15
Figure 1 shows one of the most amazing images ever taken of outerspace. It is called the Hubble Deep Field. When you look at it, you arepeering back in time up to 8 billion years, into a part of the sky thatappears no bigger than a grain of sand resting on a fingernail of youroutstretched hand! Although this picture only shows you a tiny piece of the sky, it contains a lot of information. The only stars in thephotograph are the objects that appear to have spikes. (This featureresults from the wave nature of light.) All the other objects are galaxies.
The Hubble Deep Field
15.615.6 Case Study
Figure 1
This image was captured by the Hubble Space Telescope when it was aimed toward a part ofthe sky above the Northern Hemisphere. A photograph of the Hubble Space Telescope in orbitaround Earth is featured on the first page of this unit.
History of the Universe 483
(a) What can you infer about the number ofgalaxies in the universe? (In your answer,be sure to consider the concept of the“grain of sand” mentioned above.)
(b)Which types of galaxies can you see?
The image in Figure 1 was obtained by theHubble Space Telescope over a period ofabout 100 h. It is similar to a time-lapse photothat might be taken here on Earth.
(c) Why is time-lapse imaging important whenviewing faraway galaxies?
The “optical” portion of the Hubble SpaceTelescope includes a very large mirror,specially engineered with great precision.Unfortunately, there was an error in themanufacturing that was not detected until thetelescope was launched: the curvature of themirror was out by the thickness of a humanhair, so it could not focus as well as had beenhoped. Fortunately, astronauts were able tocorrect the problem in 1993 by adding asecondary mirror during a series of spacewalks. It was a delicate but successfuloperation. Other instruments have since beenadded to Hubble, improving its performancestill further.
(d)Why are more instruments added to theHubble Space Telescope, instead of beingput into orbit separately? What might bethe advantages of each alternative?
Advanced technology is needed to keep atelescope, travelling at almost 30 000 km/hwhile orbiting Earth, aimed steadily at onetiny spot for such a long time.
(e)Why wouldn’t the telescope naturally staypointed in the same direction? Make somepredictions.
This image sees deeper into space than anyprevious image. That is why it is called the“Hubble Deep Field.” The farthest objects,which are galaxies, are up to 8 billion light-years away. Galaxies 8 billion years ago hadless structured shapes than galaxies nowappear to have. This feature helps support the Big Bang theory.
Understanding Concepts1. How was the universe different 8 billion years
ago than it is now?
2. Explain how this image allows scientists to“peer back in time.”
Exploring3. If you were responsible for aiming the Hubble
Space Telescope to take a new Deep Fieldimage, in which direction would you aim it?Give reasons.
4. Research the problems with Hubble’s mirrorand how they were corrected. Draw a labelleddiagram to explain the repairs.
5. Research the costs involved with the HubbleSpace Telescope. Do you think it is a good usefor the money? Explain reasons for your opinionin a brief letter to a science magazine.
6. Find out what other Deep Field images havebeen taken. View the images on a NASA website.
(f) Explain how the less structured shape ofearly galaxies supports the Big Bangtheory.
Astronomers observe evidence of severalgalaxies colliding with each other shortly afterthe Big Bang.
(g)Propose a reason why galaxies in the pastwere more likely to collide than they arenow.
Studying such images in more detail will helpscientists better predict what might happen tothe universe in the future.
(h)If you were a scientist studying images likethis, what would you look for? Why?
Research SkillsSKILLS HANDBOOK: 3A
3A
Challenge Connection
Students are encouraged to considerhow they might apply theirknowledge and skills to complete theChallenge later in the unit.
Skills Handbook Cross-References
References indicate to students wherethey can find added information andextra help in the skills handbook forconducting investigations, activities, andanswering questions.
