BSCS Science: An Inquiry Approach Level 3

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1 BSCS Science: An Inquiry Approach Level 3 First edition, 2010 by BSCS Unit 5 Overview 5415 Mark Dabling Blvd. Colorado Springs, CO

2 Unit Overview Nanoscience and nanotechnology are part of a relatively new field of science. More and more, we are hearing about new nanotechnology applications in the news, but often there is little information about the science involved. In fact, nanoscience is multidisciplinary, drawing from fields such as physics, chemistry, materials science, biology, and engineering. It draws from the principles of these varied fields to allow scientists to manipulate, control, and measure properties of materials at the nanoscale. This work then leads to nanotechnology discoveries, which results in these materials being used in new devices and applications. In this unit, BSCS Science: An Inquiry Approach Understanding the Science of Nanotechnology students will learn about the scientific principles that form the foundation on which nanotechnologies are developed. Chapter 1, Self-Assembly, focuses on physical science principles that are important to self-assembly, a key idea in building nanoscale materials. Chapter 2, Using Nanoscience, has a biology focus, with students examining naturally occurring nanoscale systems as well as some of the ethical questions that surround nanoscience. Students are introduced to some applications in nanotechnology, but it is important to remember that the unit focuses on developing students understanding of some of the most important principles of the science behind nanotechnology. This understanding will give them a good foundation to apply these science principles to any situation. Goals for the Unit By the end of this unit, students should understand the following: Properties of matter can vary depending on the size and the shape of the particles making up the material. Under certain conditions, atoms and molecules assemble themselves into organized structures. Electromagnetic attraction is the fundamental force that holds molecules together. The strength of the force depends on the nature and the arrangement of the particles involved. The structure of matter (for example, the shapes of molecules) is directly related to function (for example, how molecules may join together), as can be seen at the nanoscale level. Models and the use of technology are a good way to gain an understanding of processes at the nanoscale level. And while models have strengths, they also have limitations. Although nanotechnology has a variety of potential applications, there are risks that must be considered. All the units in Level 3 of BSCS Science: An Inquiry Approach reinforce specific, overarching themes. The themes are energy flow and energy transformations, and the use of models, evidence, and explanations. In Understanding the Science of Nanotechnology, students will investigate these concepts in two chapters. Understanding the Science of Nanotechnology 3

3 Strategies for the Unit Engage How Small Is Nano, Anyway? Activity Overview The goal of this unit Engage, How Small Is Nano, Anyway?, is to help students develop a conceptual reference point for the size of small objects, including nano-sized objects. Understanding the relative scales of objects that are too small to see will provide students with an important foundation for the rest of the unit. Students will learn in chapter 1 that the size and the shape of particles play a role in whether or not particles aggregate. Therefore, it is crucial that students have some idea of how big nanoparticles are in comparison with other small objects. Before You Teach Background Information As a prefix, nano- indicates any quantity times For example, 3 nanometers (nm) is meters (m). It is difficult for anyone to conceptualize how big or small a nanometer is. A proton is much smaller than a nanometer, and a cell is much larger. In this activity, students will compare large objects on a logarithmic scale with small objects on another logarithmic scale. This means that each factor-of-10 mark on the scale represents objects that are 10 times larger than objects at the previous mark. For example, an object on the 10 5 mark is 10 times larger than an object on the 10 4 mark, 100 times larger than an object on the 10 3 mark, and 1,000 times larger than an object on the 10 2 mark. You may be familiar with the ph scale. The ph scale is another example of a logarithmic scale. A ph of 9 is 10 times more basic than a ph of 8, and 100 times more basic than a ph of 7. The Richter scale for earthquakes is also logarithmic. An earthquake that measures 7 on the Richter scale has 100 times more shaking amplitude than one that measures 5 on the Richter scale. Materials For each student 1 copy of copymaster 1.1, Large- and Small-Object Size Lines For each team of 3 students 1 set of large-object cards from copymaster 1.2, Large-Object Cards 1 set of small-object cards from copymaster 1.3, Small-Object Cards (copied onto a different-colored paper from the large-object cards) Powers of 10 simulation link on the SR Web site (optional) Advance Preparation Make enough copies of copymaster 1.1, Large- and Small-Object Size Lines, so that each student will have his or her own copy. Make enough copies of copymasters 1.2 and 1.3, Large-Object Cards and Small-Object Cards, so that each team will have 1 set of each. Make each set (large and small) on a different color of paper so students don t get them mixed up. Cut out the cards and place them into sets. You may wish to laminate the cards so that they can be used from class to class and year to year. Students will work in teams of 3 for part of this activity. Select teams of students ahead of time. Educational Technologies After students do the unit Engage activity, you may wish to have them work through the Powers of 10 activity. As You Teach Outcomes and Indicators of Success By the end of this activity, students should 1. be able to conceptualize the differences in size between objects that are too small to see. They will demonstrate their understanding by ranking objects from smallest to largest and placing objects on size lines. 2. make comparisons between the size differences of objects they can see with the size differences of objects they can t see. They will demonstrate their understanding by comparing objects on two size lines (one for large objects, one for small objects) that are evenly scaled by factors of 10 and answering questions that ask them to make analogies between size differences for large objects and size differences for small objects. Strategies Getting Started Start by asking students to think about the term nanoparticle. Ask them to work as a class to come up with objects that might be the same size as nanoparticles. If they struggle, prompt them by asking, Do you think nanoparticles are big or small? Do you think people can see nanoparticles? and What are some other particles that are too small to see? Tell students that in preparation for the unit on nanoscience, they will be thinking about the relative sizes of objects in this activity so that they can have a better idea of how large nanoparticles are. Reminder of Possible Misconceptions Students may not have previously had the opportunity to compare the sizes of objects that are too small to see. They may harbor several misconceptions, including the following: Atoms are not in cells. All matter, including cells, is made of atoms. Atoms are not drawn on diagrams of cells because they are extremely small compared with the cell. The nucleus of an atom is the same as the nucleus of a cell. Understanding the Science of Nanotechnology 7

4 The nucleus of an atom is extremely dense. It is made of protons and neutrons and has a net positive charge. The nucleus of a cell is extremely large compared with the nucleus of an atom. It is an organelle of a cell, containing DNA and other important molecules for cell function. Atoms make up molecules, which in turn are used to make the parts of cells (including the cell nucleus). The word nucleus has two very different meanings. Cells and atoms are about the same size. Students tend to study cells and atoms in separate classes and never think about their relative sizes. Cells are huge compared with atoms: they are approximately 10 billion times larger. Cells are large enough to see with an ordinary light microscope. Atoms are difficult to see and require highpowered transmission electron microscopes or atomic force microscopes to get an image. Numbers on a logarithmic scale go up the same way that numbers on an ordinary number line go up. A logarithmic scale is one in which every mark is 10 times larger than the one before. An ordinary number line goes up by even amounts. So while a log scale might have the numbers 10, 100, 1,000, and 10,000, an ordinary number line would go up as 10, 20, 30, 40. Process and Procedure In Steps 1 2, students should lay the large-object cards out in front of them on the table so that the whole team can better see what the team is discussing. They may simply rearrange cards while discussing the best size order. As students arrange the order of the large objects, move around the room to get a sense of their prior understanding. If students disagree, encourage them to present evidence to their team for the order they think is correct. Don t hand out copymaster 1.1, Large- and Small-Object Size Lines, until students have completed Step 10. Students may become confused, trying to figure out the exact numerical sizes for objects. It is not necessary for students to know exact sizes; instead, students should think about how each object compares in size with the others. In Step 4, encourage students to use their own experiences when they explain why they ordered things the way they did. Students may have some difficulty with objects they have never seen. For example, it is unlikely that students have ever seen Salto Angel Falls (the largest waterfall in the world, with a clear drop of 807 m, located in Venezuela), but it is likely that they have seen waterfalls (or pictures of waterfalls). When they have difficulty with a specific object, ask them to think about the size of a similar object. In Step 6, allow students time to remind themselves what each small object is. They may need a moment to remember what a cell nucleus is compared with the nucleus of an atom. Students will then sketch each object in Step 7 so that they have a representation to go with the words. Remind students UNIT ENGAGE 8 Understanding the Science of Nanotechnology How Small Is Nano, Anyway? Matter comes in all shapes and sizes, from the smallest subatomic particles to the largest clusters of galaxies. We begin to understand the scales of objects when we are young. For example, we learn that a key is much smaller than a building. But when it comes to objects we cannot directly experience, understanding their scale becomes much more difficult. It can be difficult to think of how the size of something small compares with the size of something big. For example, how big is the width of DNA compared with the width of a human hair? If you read that a sheet of paper is 100,000 nm thick, would you be able to picture what 1 nm is? Not only is it difficult to think about how small objects compare with large ones, but it is also difficult to imagine how small things might compare with one another. You might have learned that atoms make up all matter. You might also know that cells are matter. This means that atoms must make up cells. But, when studying cells, did you ever stop to think about where the atoms are? Many textbooks will show you the organelles (mitochondria, Golgi apparatus, and so on), but they probably don t list atoms as parts of the cell. How does the size of an atom compare with the size of a cell? Understanding the Science of Nanotechnology focuses on the science of objects in a specific size range: nm. A nanometer is one-billionth of a meter (or m), but it is difficult to imagine just how small that is. Materials For each student 1 Large- and Small-Object Size Lines handout For each team of 3 students 1 set of large-object cards 1 set of small-object cards Process and Procedure that the diagrams should be very simple sketches, used to help them order the objects and remember what each is. If students get stuck in Steps 8 9, ask them probing questions. For example, if they don t know how to rank protons against cells, remind them that DNA is in a cell, and DNA is a macromolecule (a giant molecule). Then ask them, What are molecules made of? Answers to Steps 2 and 8, SE pages The correct order is listed here for your reference. Students may not have the order exactly right and should not be graded on correctness at this point: Length of a sperm cell Width of a human hair Diameter of an egg cell To understand how the sizes of small objects compare, it is helpful to make analogies between small objects and large objects. To help you make the analogies, complete the following steps with your team. 1. Place the large-object cards face up on the table. Be sure that all team members can easily see the cards. 2. Decide as a team the order for the large-object cards (put the smallest on the left, the largest on the right). If you don t know where to put an object in the ranking, make your best guess. Don t worry about exactly how big each object is. Instead, simply rank the objects from smallest to largest. 8 Understanding the Science of Nanotechnology

5 Width of a dime Height of a human being Distance between bases in a baseball diamond Height of the Eiffel Tower Height of Salto Angel Falls Height of Mount Everest Length of Trans-Canadian Highway Diameter of Earth Distance from Earth to the Moon 8. Once again, the correct order is listed for your reference. Students should not be graded on correctness at this point: Proton Nucleus of a gold atom Gold atom Sugar molecule Width of DNA Gold nanoparticle Cell nucleus Length of a sperm cell Width of a human hair Diameter of a human egg cell Width of a dime In Step 11, hand out copymaster 1.1, Large- and Small-Object Size Lines. Students should write the names of the objects in the teamselected order on the size lines. Don t worry if students don t have the order of the objects exactly correct. The goal is to get them thinking about relative sizes. However, if they are way off in their order (e.g., they placed the diameter of Earth so it is smaller than the length of the Trans-Canadian Highway), try to redirect them by asking probing questions such as, Do you think the highway is mostly straight, or do you think it loops around the country? and Does the highway fit on Earth? Similarly, if students are way off on the small objects, ask them probing questions (like those above) until they have the basic order: atomic-sized objects, molecularsized objects, and cellular-sized objects. In the Refl ect and Connect questions, students should make analogies for comparing the sizes of small objects by comparing the sizes of large objects. They will likely need some help understanding that those objects that align approximately vertically from the small-object size line to the large-object size line can be analogues for one another. Carefully walk them through the example using gold, a gold nanoparticle, a human, and the Eiffel Tower, which has been done for them. Notes: 3. Write the order of large objects in your science notebook, from smallest to largest. 4. What reasons did you have for ranking some objects as bigger than others? In your science notebook, write your ideas for a few of the objects. For example, from looking at a globe, you can see that the width of Canada takes up less than one-third the circumference of Earth. So the Trans-Canadian Highway (a highway that crosses Canada) must be less than the diameter of Earth (diameter circumference, or about one-third the circumference). 5. Place the small-object cards face up on the table. Be sure that all team members can easily see the cards. 6. Discuss with your team what each object is. 7. In your science notebook, sketch a picture of each object and label it, keeping in mind the sizes of the objects. For DNA, consider its width, rather than its length. For a sperm cell, consider its length. Draw the smallest things as the smallest-sized pictures. For example, DNA fits inside the cell nucleus, so DNA should be drawn smaller than the cell nucleus. Don t worry about making your pictures exact, just make a very simple diagram to remind yourself about what each object is. 8. Decide as a team the order for the small-object cards (smallest on the left, largest on the right). Don t worry if you don t know the exact sizes of the small objects. Your goal is to rank them from smallest to largest. 9. Write the order of the small-object cards in your science notebook, from smallest to largest. 10. What have you learned about the objects that helps you decide which objects are bigger or smaller than others? Write a few of your ideas in your science notebook. It is OK if you don t know how to rank some of them. For example, you could write, From the hint and what we have learned about cells, we know that DNA fits inside the cell nucleus. This is why we think DNA must be smaller than the cell nucleus. 11. Obtain the handout Large- and Small-Object Size Lines from your teacher. Write the objects on the large-object size line and the smallobject size line, going from smallest to largest on both size lines. 12. Use the handout Large- and Small-Object Size Lines along with the Size Line Protocol to answer the following Reflect and Connect questions. The 2 size lines (large object and small object) change scale by the same increments. Protocol Understanding the Science of Nanotechnology 9 Understanding the Science of Nanotechnology 9

6 Notes: Answers to Reflect and Connect, SE page See figure TEn1.1 for possible entries. 2. Nano-sized gold particles are not the smallest particles that exist. Many things are much smaller than gold nanoparticles, including atoms, nuclei, protons, and electrons. 3. Students should recognize that they considered the big idea of size and scale. They were getting an idea of how big nano is in order to better make sense of science at the nanolevel. Protocol Size Line Protocol The large- and small-object size lines can be used to help you understand the differences in the sizes of objects that are too small to see. On both size lines, each mark labeled with a 10 is 10 times larger than the previous mark. This means that the objects on the large size line can be used to make analogies for the objects on the small size line, as long as you compare objects that align vertically. The objects on the top line are 10 billion times larger than the small objects they align with vertically. Using the size lines will help you understand how the sizes of objects compare, even if they are all too small to see. Step 1. Choose 2 small objects that you would like to compare in size. Step 2. Choose 2 large objects that most closely align vertically with the 2 small objects. Step 3. Make an analogy: the 2 small objects compare in size the same way the 2 large objects compare. For example: Gold atoms on your diagram align vertically with average human height. So if a gold atom were scaled up so that it were 10 billion times its original size, it would be as tall as a human being. If a gold atom were a human being, then a gold nanoparticle would be the Eiffel Tower. Now you can imagine how much bigger a gold nanoparticle is compared with a gold atom. Just imagine the difference between the height of the Eiffel Tower and that of a human being! Reflect and Connect 1. Copy the analogy table in figure En1.1 into your science notebook and complete it. The first row is done for you as an example. 2. Are nanoparticles the smallest particles that exist? Why or why not? 3. Which big idea of nanoscience did you consider in this activity? 10 Understanding the Science of Nanotechnology 10 Understanding the Science of Nanotechnology

7 Objects If the first small object were the large object..., then the second small object would be second large object. Picture 1. Gold atom 2. Gold nanoparticle If gold atoms were human beings, then gold nanoparticles would be the Eiffel Tower. gold atom human being gold nanoparticle Eiffel Tower 1. Proton 2. Gold atom If protons were as big as the width of a human hair, then gold atoms would be as large as human beings. 1. Proton 2. Width of DNA If protons were as big as the width of a human hair, then the width of DNA would be as large as the distance between bases in a baseball diamond. 1. Proton 2. Diameter of a human egg cell If protons were as big as the width of a human hair, then the diameter of a human egg cell would be as large as the Trans- Canadian Highway. Figure TEn1.1: Reflect and Connect Question 1. The main goal is to have students make analogies using the table. Don t worry if their answers are not exactly correct. Understanding the Science of Nanotechnology 10a