Author: Connie Hubbard, Sandra Van Natta, AGPA staff
A nanometer is one billionth (1 x 10-9) of a meter which can be about 3 to 5 atoms in width. Electrospun nanofibers produced from polymer solutions are being used in unique ways by scientists. Nanotechnology allows the manipulation of matter, atom by atom at the "nanoscale." Properties of these materials are amplified due to the fact that many fibers can fit into a very small space. Scientists have found many unique ways to use such fibers from producing new materials capable of blocking moisture, removing of toxins from both water and air, delivering medicines to a specific region in or on the body, and tissue scaffolding. The possibilities are endless as scientists and inventors produce new products formed from these extremely small fibers.
In this investigation students will determine the advantages of going "small" by comparing the amount of chocolate syrup coating on a large diameter pretzel to that of an equal volume of smaller pretzels coated with chocolate. Students will learn what happens to the surface area as the diameter gets smaller and smaller. Students will determine what advantages exist in making the size (diameter) of a pretzel smaller. Students will make the comparison by massing a cup of chocolate syrup before and after dipping the pretzel(s). Students will use their data to support their conclusions. The lesson contains a PowerPoint review of the metric system with pictures to help students visualize large and small number lengths. Using a second PowerPoint set of slides in the elaboration, the teacher can relate the activity to the new field of nanotechnology and discuss with students why it is advantageous for newly developed materials to be so small. This often has to do with the large surface area available on nanosized particles and fibers.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Per group of students:
Begin the lesson by showing students pictures (or actual objects) of first-generation technologies and more recent examples. Pictures of a video-tape along side a DVD and a television that used cathode ray tubes along side a flat screen television are available by clicking here. Discuss with the students these examples of developments in electronics products (technologies) that have become possible due to our new ability to "do more" in ever smaller spaces. Explain to students that in this lesson they will be exploring the advantages of going small and learning about application in the new field of nanotechnology.
The teacher should begin with a demonstration:
Teacher Demo: Dip 1 small diameter pretzel in chocolate syrup and then do the same for one large one large pretzel. Dip to the same depth. Ask students which would have the greater amount of chocolate on the surface of the pretzels. Most will say that the larger pretzel will have the most chocolate. Then say "What if I use 3 small pretzels which combined are about the same diameter as the large pretzel? Which will have more chocolate on the surface?" Have students write down their prediction. Then introduce students to the laboratory activity where they will gather mass measurements to determine which group has the greater amount of chocolate.
Assessment A quick assessment of understanding can be done by taking a hand count of ideas. Ask how many students believe that there will be no difference; how many think the larger pretzel will contain more chocolate; and, how many think the smaller pretzels will contain more chocolate.
In the following activity students will determine what advantages exists in making the size (diameter) of pretzel smaller. Students will compare the amount of chocolate covering a large diameter pretzel with that of smaller pretzels that take up about the same diameter. Students will make the comparison by massing their cup of chocolate before and after they dip the pretzel(s) in chocolate.
Procedure: Give the following directions to the students
Assessment Monitor the students as they work to be sure that they are following procedures and working safely.
Let students suggest what should be in the table. Remind them to use labels. Have students post their data on the board or overhead projector. They can easily find their mistakes that way. Doing this in a constructive manner builds trust within the classroom. Allow students to have their work checked before posting, if desired by the student.
A sample data table could be:
As students look at their class data, they can average the chocolate coatings for each group. Point out that scientists draw conclusions based on as much data as possible. If a students' individual data does not match the class average (which will be typical), this will give the teacher an opportunity to discuss trends and probability, experimental design and sources of error.
Review the metric system of measurement and the prefixes that when affixed to "meter" describe very large to very small units of length. Show the PowerPoint presentation entitled, What is the Meaning of "Nano" in Nanotechnology?
Assessment Student should answer the following questions as written responses to the lab data:
A. Use one large paper straw and a number of smaller straws equivalent in volume to help students understand surface area compared to volume. Since the volume is constant, you can focus just on the surface area of the straws. The lengths of the straws are also constant. Cut the straws open with an exacto knife, flatten them and tape them to an overhead transparency. Have student volunteers measure the length and width dimensions. The class can calculate the areas by multiplying the length times the width. Data will show an increase in surface area when the areas of the smaller straws are added together and compared with the larger straw's surface area.
B. Conduct a discussion of the applications of nanotechnology after showing the PowerPoint presentation, Nanotechnology and Nanofibers.
Students should have some knowledge of metric units and prefixes.
Students should know how to correctly mass objects and record these values in a data table.
Students should be able to locate and describe the diameter, length, surface area and volume of an object.
Common Core Standards:
Metric prefixes (students will need to have nano and micro defined)
Metric measurement - using an electronic balance
Recording data correctly with the appropriate unit
Geometric concepts: volume, surface area, diameter
Remind students not to eat pretzels or the chocolate used in the experiment.
Nanotechnology allows the manipulation of matter, atom by atom at the "nanoscale." Properties of these materials are amplified due to the fact that many fibers can fit into a very small space. Scientists have found many unique ways to use such fibers from producing new materials capable of blocking moisture, removing of toxins from both water and air, delivering medicines to a specific region in or on the body, and tissue scaffolding. The possibilities are endless as scientists and inventors produce new products formed from these extremely small fibers.
Additional information about nanotechnology and nanofibers is found in the PowerPoint presentation, Nanotechnology and Nanofibers.
Both performance and written assessments within this lesson will allow the teacher to determine student learning. Students should be able to measure correctly using metric instruments. They must graph variables and answer questions which demonstrate understanding of the concepts.
Grouping Suggestions: Recommended for groups of 2 or 3 students.
Pacing/Suggested Time: 2-lab periods of 43 minutes; Reflection and Discussion (10-15 minutes)