• A unique and useful property of carbon is its ability to chemically join with other carbon atoms. This bonding ability is based on the four single electrons in the outer energy level of each carbon atom. Each of these electrons enables a carbon atom to chemically join with another carbon atom—or with an atom of a different type.
• If a carbon atom shares a pair of electrons with another type of atom (one electron
from the carbon atom and one from the other atom), the bond formed is a single bond. In methane (CH4), carbon forms four single bonds with four hydrogen atoms. If
carbon shares two pairs of electrons with another atom, a double bond forms. Carbon forms two double bonds with two oxygen atoms in carbon dioxide (CO2). Sometimes,
carbon shares three pairs of electrons with another atom, forming a triple bond. In acetylene (C2H2), a triple bond exists between the carbon atoms, and a single bond
exists between each of the two carbon atoms and the two hydrogen atoms.
Fullerenes
• In addition to charcoal, graphite, and diamond, carbon atoms also form molecules called fullerenes. Fullerenes are named after R. Buckminster Fuller, a U.S. architect and inventor, who built and popularized geodesic domes. These domes have shapes similar to that of a soccer ball.
• The first fullerene to be discovered was C60, known as a buckyball, after Buckminster
Fuller. In this molecule, 60 carbon atoms each bond to three other carbon atoms. This bonding arrangement forms alternating pentagons and hexagons, resulting in a shape that is quite similar in appearance to that of a soccer ball or geodesic dome.
• The buckyball is not the only fullerene. The fullerene C70 is not uncommon, and
fullerenes with up to 100 carbon atoms have been discovered. Fullerenes can also have different shapes. In addition to the soccer-ball shape, the atoms can form tubes, planes similar to those in graphite, and other shapes.
• When scientists first discovered fullerenes, they hoped that the new carbon substances could be used as lubricants or as carriers for reactants or medicines. However,
practical uses for them have not yet been realized. Some fullerenes have been shown to be superconductors at extremely low temperatures, but possible commercial applications have so far eluded researchers.
POSSIBLE MISCONCEPTIONS Identify
• Students may think that diamonds’ only use lies in the fabrication of jewelry.
Clarify
• Although many diamonds are used for jewelry, many are also used in industry. Because of diamond’s hardness, it is used in cutting and grinding tools. A diamond can cut or smooth almost any other material. Many industrial diamonds are synthetic—made in labs—instead of mined from the earth.
Ask What They Think Now
• At the end of the lesson, ask, What are some important uses of diamonds?
Students should realize that diamonds are used to make jewelry and to make industrial cutting tools.
TEACHING NOTES Engage
• To relate this lesson to students’ previous knowledge, have students look at Figure 1 on page 241 of the Student Book and read the caption. Ask students to share their experiences with and knowledge of charcoal, pencil “lead,” and diamonds. Make sure they focus on the different properties and uses of the three substances. Remind them that each element is made of a different atom, and that elements have unique
properties. Ask, How can one type of atom—carbon—form such different substances?
Explore and Explain
• have students read the introductory paragraph of the section, followed by the sections,
Charcoal, Graphite, and Diamond. Have students compare and contrast the carbon
structures shown in Figures 2 and 4 on pages 241-242 of the Student Book. Ask, How are the structures similar? How are they different? Make sure students see that
graphite consists of sheets of interconnected hexagons, while diamond consists of interconnected tetrahedrons. Ask, What do the dotted lines in Figure 2 represent?
(They show that the sheets of graphite lie on top of one another but are not chemically interconnected.)
Try This: Copper-Plate Your Pencil
Skills: Performing, Observing, Analyzing, Communicating
Purpose: To show that graphite conducts an electric current by electroplating a graphite
electrode
Equipment and Materials (per student): eye protection, apron; per group: 9 V battery;
medium-sized beaker; graduated cylinder; 2 electrical wires; 2 pencils with both ends sharpened; copper(II) sulfate solution
Student Safety
• Copper (II) sulfate solution is a skin and eye irritant, so make sure students wear eye protection and aprons. Have students wash their skin immediately if they come in contact with the solution.
Notes:
• You may want to provide electrical wires with alligator clips on both ends, as students may find them easier to attach to the battery and pencils.
• The solution does not require distilled water. Any ions present in tap water should not
affect the results.
• Explain that because graphite conducts an electrical current, the pencil graphite
connected to the negative pole of the battery is also negative. It attracts the positive copper ions (Cu2+) in solution. Excess electrons from the electrode move to the copper ions, changing them to the copper metal that is seen on the electrode. Another reaction that involves the negative ions in solution occurs at the positive electrode.
Suggested Answers:
A. A dark material began coating the pencil lead connected to the negative terminal of the battery. Bubbles formed on the pencil lead connected to the positive terminal of the battery.
B. Yes. A dark, reddish, powdery solid formed on the pencil lead. C. The copper came from the copper sulfate solution.
D. The copper only formed on the pencil lead when the battery was connected.
E. Graphite is made of a non-metallic element, carbon. Carbon has many of the typical properties of non-metals, but as graphite, has an unusually high electrical conductivity. F. Graphite is a good lubricant because of the way its layers can slide past one another. It
is also used as an electrode in dry cells and batteries.
• As a class, discuss the role of diamonds in today’s society. To explore this topic, have students complete Research This: Artificial Diamonds.
Research This: Artificial Diamonds
Skills: Researching, Analyzing the Issue, Communicating, Evaluating
Purpose: To research industrial uses of diamonds, the manufacture of diamonds, and
differences between artificial and mined diamonds
Notes:
• Challenge students also to investigate the economics of diamonds. Ask questions such as the following: How does the cost of artificial diamonds compare with the cost of mined diamonds? What about the social and environmental costs of the two kinds of diamonds? How have artificial diamonds affected the market and price of mined diamonds?
Suggested Answers:
A. Answers will vary. Students should note that people can choose whether or not to value gem-quality natural diamonds over gem-quality synthetic diamonds. If a market for natural diamonds endures, mining for them provides many jobs, but also presents controversies such as those surrounding blood diamonds.
B. Artificial diamonds have only one main disadvantage: they are not natural. In almost all other respects such as cost, hardness, appearance, and applications, they are equal or superior to natural diamonds.
C. Answers will vary. Students may or may not feel that the lower cost and beautiful appearance of artificial diamonds offsets their industrial origin.
Extend and Assess
• Revisit Figure 1 on page 241 of the Student Book. Have students discuss the three forms of carbon again, reflecting on what they have learned in this lesson. Ask volunteers to describe some of the properties of each carbon form and to relate the properties to the underlying arrangement of carbon atoms.
• Conclude the lesson by brainstorming ideas about ways the Canadian government and diamond mining companies could work together to mitigate environmental damage caused by mining operations. Have students discuss whether environmental damage is ever truly irreversible.
READING TIP
Revise Your Inferences
• Point out that the process of revising one’s inferences may happen almost
imperceptibly, going by practically unnoticed. But often it is accompanied by a short, mental “Aha, now I understand!” Have students review the chapter, looking for places where they learned something that upset some previous inference. Ask them to share these moments with the class.
Check Your Learning Suggested Answers
1. Carbon atoms are joined in a shapeless, disorganized fashion in charcoal. In graphite, the carbon atoms form in sheets of interconnected hexagons, while in diamond, the carbon atoms join in a never-ending, very regular three dimensional structure. 2. When a pencil lead is pressed against a piece of paper, the surface sheets of the
graphite slide onto the paper to make a mark.
3. Diamond mining creates many jobs and brings businesses to the area.
4. While diamond mining is less environmentally damaging or polluting than gold
mining, it has destroyed streams and drained lakes. Topsoil that is removed also has to be restored, and soil removal can damage permafrost regions permanently.
5. Diamonds are one of the hardest known materials and are used for cutting, drilling and polishing processes. Their transparency makes them sparkle; this and their various colors make them a valuable gem stone.
6. (a) Graphite is electrically conductive and is best suited for an electrode in a battery. (b) Owing to its hardness, diamond is best suited for drilling operations.
(c) Charcoal would be most suited for burning as fuel to produce thermal energy.
DIFFERENTIATED INSTRUCTION
• Have students with an interest in economics research the history of diamond mining and diamond cartels. How has diamond mining changed in the last 100 years? How is mining different in Africa, Australia, and Canada? How has the diamond cartel affected the development of diamond markets?
• Have bodily/kinesthetic learners use molecular modeling kits to model the structures of graphite and diamond. If modeling kits are not available, students can use
Styrofoam balls and toothpicks. Have students press on the side of the graphite model to show how the layers slide across each other. Have them press lightly down on the diamond structure to show how stable it is. Challenge them to relate the structures of these forms of carbon to their properties and uses.
• Have verbal/linguistic learners debate the pros and cons of diamond mining in
Canada. Make sure they visit the Nelson Science website and investigate the careers of diamond miner and environmental assessment professional. They may want to assume these roles for the debate. Be sure they consider the economic, environmental, and social dimensions of diamond mining.
ENGLISH LANGUAGE LEARNERS
• Have English language learners pair with students who are proficient in English to read about diamond mining in Canada. Have both students then research any mining that takes place in the native country of the English language learner. Ask, What negative effects does mining have on the environment in your home country? Is anything being done to prevent or repair the damage? How does the mining affect the economy of the region? How are the environmental and social effects of mining different in your country than in Canada? Have the students work together to write a
TECH CONNECT Stronger Than a Speeding Bullet Time
30 minutes
Literacy Resources Assessment Resources Other Program Resources
Nelson Science Perspectives 9 website
www.science.nelson.com
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KEY CONCEPTS