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NOVA scienceNOW: Diamond Factory

Viewing Ideas

Before Watching

1. Discuss the implication of growing diamonds: In the NOVA scienceNOW video segment, Neil visits a "diamond farm"—a secret location where the diamonds are "chemically, physically, and optically identical to mined diamonds, with one exception. [They] grow them." So, what are the implications of growing diamonds?

   • What is a diamond?
   • Where do diamonds come from?
   • What are they used for?
   • What are diamonds valuable?
   • Will mined diamonds be worth less if identical diamonds can be grown? For example, would a diamond ring be worth less if the diamond were grown instead of mined?
   • What might happen to the value of diamonds if grown diamonds become commonplace?
   • What might be the benefits and drawbacks of growing diamonds?

2. Build molecular models of diamond and graphite: Before class, obtain molecular modeling kits, or gather materials such as toothpicks, pipe cleaners, gumdrops, marshmallows, and clay. In class, instruct students to look up the bonding angles for diamond and graphite and build models of the molecular structure of these two substances. Have them work to make the models as accurate as possible and label the bonds with the correct angle measurement. (Molecular modeling kits will more accurately show the atomic arrangement, but do-it-yourself materials are suitable.) Then have students visit the following NOVA Web sites and compare the molecular structure of diamond and graphite, the density of the atoms, and how they interlock. Finally, discuss why diamond is so much stronger than graphite.

   • The Structure of a Diamond
   • The Structure of Graphite

   The molecular structure of diamond is based on a pyramid. Each carbon atom bonds with four other carbon atoms, locking together in a tight, stable pyramid shape. Each of these four atoms also becomes part of a neighboring pyramid, creating continuous, interlocked matrix of carbon atoms. As discussed in the episode, this makes diamond "one of the hardest substances known." Graphite, too, is made from carbon atoms. But in graphite, each carbon atom bonds to only three other carbon atoms, and they do so in a plane. The planes bond to each other only weakly, making graphite a very soft material. Also, diamond is chemically stable because the outer electron shell of each carbon atom is full. In contrast, the outer electron shell of each carbon atom in graphite is not full. There is one electron position open, making graphite less chemically stable than diamond.

   Extension — Understanding pencil "lead": Pencil "lead" is a misleading term—there is actually no lead in a pencil. Instead, the writing material in most pencils is a mixture of graphite and clay. The hardness is determined by the amount of clay, and this hardness is reported on the side of the pencil (e.g., the infamous "Number 2"). Have your students press a fingernail into the "lead" of pencils of various hardness and consider how easy or difficult it is to scratch the writing material. Also have them make marks on paper with the pencils and consider how dark the marks appear. In general, the higher the number on a pencil, the more clay is used, which produces a harder writing material and a lighter mark on the paper. A #2 pencil, with its relatively low proportion of clay, will typically be very easy to scratch and will leave a dark mark. This is why #2 pencils are desirable for use on standardized tests.

After Watching

1. Consider the pros and cons of growing diamonds: Ask students to update the lists they created earlier with new ideas from the episode. For example:

   • What could grown diamonds be used for?
   • Would these new applications make diamonds more or less valuable? Why?
   • How could having a diamond in a cell phone affect the value of diamond in a ring?
   • Why might natural diamonds be more desirable and valuable than grown ones for rings?
   • What are the advantages of being able to tailor the shapes, chemistry, and physical properties of a diamond?
   • Have your thoughts changed on whether or not growing diamonds is a good idea?

2. Compare how different materials transfer heat: In the video segment, Jim Butler of the Naval Research Lab has Neil hold plastic, copper, and diamond against a block of ice to test how quickly diamond conducts heat. Although you don't have classroom sets of diamonds, you can still have students try parts of this demonstration and extend the exploration to show how different materials conduct heat at different rates.

   Before class, gather materials to test, such as ice cubes and plastic cards, copper pennies, wood, glass, cardboard, and washers made from metals other than copper. Try to get objects that are about the same thickness and length, if possible. In class, form teams and have students repeat Neil's experience with plastic and copper. Then have them predict which of the remaining materials will be the best and worst conductors. Have teams record their predictions and reasoning. Next, ask them to time how many seconds it takes for each material to transfer heat from their fingers to the ice cube. What are the effects on the ice cube? Which materials conduct heat? Which conducted heat fastest? Have each team arrange the materials from best conductor to worst and compare their order to that of another team. If teams drew different conclusions, have them test those materials again and consider what might have caused the differences. Finally, have teams compare their results to their predictions. Were they right about what materials would be the best and worst conductors? How does what they've experienced relate to their initial reasoning?

   The video demo and students' testing are not rigorous experiments with controlled variables and quantitative measurements. Challenge students to find several ways to improve this experiment. (For example: making all the materials the same size and thickness; holding all the materials at a point the same distance from the ice; timing accurately; using measurement tools that offer more precision than simply feeling with fingers.)

   End this exploration with a brief discussion on why it's important to control variables and use quantifying measurements in research. Why does it matter that different materials conduct heat at different rates? And why might it be significant that diamond is a fast conductor of heat?

   Extension — Conducting Heat: Perform a conduction experiment with a heat source instead of the ice cube used in the video demo. Gather the following materials: bowl, metal rod, plastic rod, wooden rod, glass rod, butter, and plastic beads. Using a small amount of butter, attach a bead to each rod at the same distance from an end. Fill the bowl with hot water, and dip in the bead-less end of each rod. Observe how long it takes for the butter to melt enough to release the beads, and discuss why it is happening.

3. Test the electrical properties of materials: According to the video, diamond "has impressive electrical properties." For example, "a centimeter-thick plate of diamond can withstand ten million volts of electricity" and "when you put boron in, you can now get electricity to flow through the diamond."

   Before class, gather a class set of materials for creating a simple circuit: a battery, a bulb, and wire. Also gather materials for testing electrical conductivity, such as wood, glass, plastic, cardboard, rubber, metals, graphite (such as a pencil lead), water, salt water, etc. Review with students how electricity flows through a circuit. Then, have students build and test their simple circuits and experiment with the various materials. Have students make qualitative determinations about which materials conducted electricity well, which conducted electricity poorly, and which don't seem to conduct electricity at all. After the exploration, discuss the electrical properties of diamonds, both as insulators (when pure) and conductors (when boron is added).

   Extension — Transistors: A transistor, vital to so many of today's electronic devices, is a semiconductor that amplifies an electrical signal and/or serves as an electronic switch. As the program noted, "diamond has the ability to switch much higher frequencies, much higher voltages" than silicon, the current choice for transistors. Learn more about the history and importance of transistors with information, audio and video clips, and teacher resources from the PBS: Transistorized! Web site at: http://www.pbs.org/transistor/index.html.

4. Envision the future: The video presents a possible future in which the silicon in our current electrical devices is replaced by diamonds, making the devices smaller, lighter, faster, and cooler. Have your students brainstorm potential devices that could be developed if electronics could be made really, really small—e.g., small enough to be implantable—while being powerful enough to work like a high-end computer. Ask students to take one idea and expand on it. For example, maybe they'd want to implant a music player in their heads Expanding on this idea might including thinking about how such a device would be turned on and off, how it would be upgraded, and/or how other people would know that someone had this device (since possessing the latest technology is something many people want to show off!).

5. Investigate the structure of crystals: As explained in the video, "for scientists, what's most exciting about growing diamonds is not how you can make them just like natural stones, but how you can make them DIFFERENT." In particular, the power is in the idea that we could "manufacture diamonds and guarantee they'd all be exactly the same" and "engineer the material to have the property match the application that we need."

   Unfortunately, we can't have students experiment with making diamonds in schools. However, your students may be able to make another type of crystal—salt. Before class, gather for each team the materials necessary for producing the crystals: beaker, water, salt, vinegar, sponge, and small shallow dish. Supervise students as they boil 8 ounces of water. Once the water is boiling, have each team turn the heat off, add 1/4 cup of salt and 2 teaspoons vinegar to the water, and stir until the salt is dissolved. Have students put the sponge in the dish and pour enough of the solution over the sponge to saturate it. There should also be a small amount of solution in the dish. Place the dish in a spot where it will not be disturbed and check daily for salt crystals (it should takes a day or two for them to form). Have students compare their crystal formations. How are they alike? (Cubic shape, color) How are they different? (Size, imperfections) What do students notice about the shape of the crystals and the way in which they formed? (Regular, symmetrical, formed through evaporation)

Extensions

• Diamonds in Electronics Podcast: Listen to the NOVA scienceNOW podcast that addresses the strengths and limitations of diamonds regarding the use of diamonds in electronics . This podcast overlaps with parts of the video segment, but it also takes various concepts further and presents some new ideas. Play this podcast for your students and extend the discussion.

• Diamonds on NATURE: Watch the episode on diamonds in the PBS Show NATURE. Assess information, interactives, and video segments related to this show online at http://www.pbs.org/wnet/nature/diamonds/index.html. Topics include how diamonds are made in nature, how diamonds are cut, and an earlier approach to making diamonds in the lab. Explore these resources with your students and extend the discussion.

Activity Author

Teon Edwards is a curriculum developer with a background in astrophysics, mathematics, and the use of technology and multimedia in teaching and learning. Since 1996, she has developed numerous science and mathematics education materials for school, home, and informal learning environments.