By Jeffery Patterson and Brandy J. Merwin 22 L T h e S c i e n c e Te a c h e r earning cycle investigations allow science students to model the activities of real scientists. An important step in modeling is data collection, which can present a problem in an astronomy course. The celestial body being studied often is unobservable for various reasons.
In past classes students studying the solar system have encountered a number of dilemmas with data collection. First, several planets usually are in transit behind or in front of the Sun, making it impossible for students to observe them. Second, planets are observable only at night or early in the morning when school is not in session. Finally, we simply did not have the equipment required to observe planets and gather data. Because students cannot directly experience the characteristics of each planet, I traditionally have required them to gather data by researching information at the library and creating a report about a particular planet. Students found this activity tedious and pointless because it did not provide them with an application. Listening to the same report every class period also made the lesson repetitive and boring for me. The activity was an inadequate and unacceptable solution to the data collection problem. To help correct the situation, this year I added a new twist to the activity. We used the learning cycle to develop the following concept: The planets can be classified as terrestrial or Jovian based upon their characteristics. The learning cycle has three phases. In the first phase, exploration, students gather data. Students then organize and analyze data to develop a concept during the term introduction phase. Finally, the concept is integrated and extended through the concept application phase (Marek and Cavallo, 1997). Students obtain a better understanding of the terrestrial versus Jovian planet concept using the three-phase learning cycle. Exploration I began this exploration by asking students to predict how the planets should be classified based on their prior knowledge. Typical answers involved grouping the planets by size or distance from the Sun. These answers were incomplete and it was time for my students to gather data. Because a field trip to Mars is out of the question, the next best data source is the Internet. This investigation takes advantage of how readily available technology is. The class is divided into groups of two, and each group is assigned a planet to research. Students navigate a series of designated websites and complete a data chart for their assigned planet. Each group of students considers its FIGURE 1 Assessment Rubric Criteria 3 2 Point Value 1 0 Content Information is complete, accurate, and in appropriate SI units. Information is mostly complete and accurate and is in appropriate SI units. Information is incomplete and inaccurate. Data are presented using inappropriate units. Visual Presentation data is concise and well organized. Pictures and diagrams add to presentation and illustrate key points. data is concise and somewhat organized. Pictures and diagrams add to presentation. data is lengthy and disorganized. Pictures and diagrams are absent or do not relate to presentation. Oral Presentation Presenter speaks clearly and concisely. Speaker uses appropriate volume and tone. Presenter maintains eye audience and uses appropriate posture. Presenter is not as clear or concise. Speaker uses appropriate volume and tone. Presenter makes eye audience occasionally and usually uses appropriate posture. Presenter does not speak clearly or concisely. Speaker uses inappropriate volume and tone. Presenter does not maintain eye audience and uses inappropriate posture. May 2002 23
FIGURE 2 Data chart for planets. As students discover special characteristics of each planet, they may develop a comparison chart similar to the following: Planet Diameter Mass Density Temp Composition Atmosphere Revolution Rotation Moons Points of Interest Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto planet s mass, diameter, temperature, composition, rotation, revolution, and number of moons. Since it is important for students to gather and record their data in a systematic and accurate manner, I encourage groups researching the same planet to compare data. This helps clarify any discrepancies within their research. The second component of this exploration involves organizing and presenting the data. In an effort to motivate all of my students, I ask them to display the information they gather on their planet in a collective manner. Each group creates a presentation on its designated planet. Groups are given a rubric that I use to assess their presentations (Figure 1). The rubric ensures that the data chart for the planets (Figure 2) is completed accurately and in 24 T h e S c i e n c e Te a c h e r an orderly fashion. The data from the presentation play a critical role in enabling students to construct the concept in the term introduction phase. Term introduction The Planets at www.scilinks.org Enter code: TST50201 After completing the previous activities, students consider a series of characteristics that enable them to analyze data collected about each planet (Figure 3, page 25). Each group is given a set of planet cutouts designed to provide a visual aid for the students. Students then group the planet cutouts in piles for each parameter in the data table. For example, students compared the diameters of the planets and grouped the planets accordingly.
Typically, four groups are selected: Pluto, Mercury, and Mars; Earth and Venus; Uranus and Neptune; and Jupiter and Saturn. Students detect similar patterns for each parameter. After students compare and cluster the planets based on each characteristic, I display their data on the board. Students determine if any planets consistently appear in a group by themselves Pluto often appears alone. Students then try to determine if any planets are grouped consistently together. After careful analysis, students determine that Mercury, Venus, Earth, and Mars can be grouped together based on their characteristics. The students also find that Jupiter, Saturn, Uranus, and Neptune are consistently grouped together. With this information, students can see why the planets can be classified as either terrestrial or Jovian. The first four planets are terrestrial because of their proximity to Earth and their similarly rocky, metallic composition. The latter four planets, from Jupiter through Neptune, are Jovian because of their physical resemblance to Jupiter. Concept application At this point, students have a better understanding of the planets and how they are classified, so an in-depth FIGURE 3 Group application goals. By using the learning cycle in the activity, students should be able to: 1. Group the planets by mass. 2. Group the planets by density. 3. Group the planets by diameter. 4. Group the planets by rotation. 5. Group the planets by their number of moons. 6. Group planets consistently together. 7. Determine which planets are consistently found by themselves. 8. Compare the composition of the planets that are consistently grouped together. Determine similarities. 9. State characteristics used to determine in which group the planets belong. 10. Consider the planets that have rocky compositions and determine which planet they resemble. 11. Consider the planets that have gaseous compositions and determine which planet they resemble. 12. Compare and classify the planets that most resemble Earth. 13. Compare planets similar to Jupiter. 14. State the main idea of this investigation. discussion of the other celestial bodies within the solar system can occur. Examples of questions that can be used to generate this discussion are Where do comets fit into our classification system? and How could you extend our classification system to other members of our solar system? The following activities provide students with an understanding of these celestial bodies and their composition. The first concept application activity involves making a comet. This activity helps students make a direct May 2002 25
correlation between the data they gathered on the planets and the composition of comets. To demonstrate the life cycle of a comet, I combine crushed dry ice, dirt, and ammonia in a chemical hood with a vent and take safety precautions. These materials are placed into a plastic bag, and using insulated gloves, I mash these substances together to construct dirty snowballs. As I assemble the comet, students observe its birth and death. Students discuss the composition of comets and compare this with the composition of planets. The second concept application activity continues this theme by comparing compositions of other celestial bodies. Because our solar system consists of more than planets and comets, the next concept application activity involves asteroids, meteors, meteorites, and meteoroids. Students then analyze the composition of these leftover drifters of the solar system and compare them to the planets composition. One objective of this investigation is to guide students toward discovering the solar system and its components for themselves. This is accomplished through the previous phases. Another objective is to put the planets sizes and arrangement in the solar system in perspective. The 500 m solar system is designed to accomplish this task. I develop a scale (1 m = 2,840,000 km) that students use to create a model that shows them how large or small planets are in comparison to each other and the Sun, and the distance each planet is from the Sun. Students are given a series of cards that represent the planets size and distance from the Sun. They then create a model solar system based on these dimensions. I add a few cards representing comets and asteroids to test students understanding of these celestial phenomena and where they occur. The final concept application activity involves reading a current magazine article that discusses the possibility of another planet that either exists or existed within our solar system. Students read the article and respond to a series of questions (Svitil, 2001). After completing the reading, students are assessed on their understanding of the concept that planets are classified by their characteristics as either terrestrial or Jovian. Assessment To check for understanding of the concept, I bring students back to Pluto. They already have determined that Pluto seems out of place, so students consider the anomalies surrounding Pluto by writing answers to the following questions: If Pluto is a planet, then how would you classify Pluto? Provide evidence for your conclusion. If Pluto is not a planet, then what is it? Why? Provide evidence for your conclusion. The purpose behind this learning cycle based activity is to have students collect accurate and current data about the planets. Using the Internet makes this possible. This method of data collection provides solutions to problems encountered during previous investigations of the planets, such as the position of the planets, time that the planets are unobservable, and the lack of proper equipment to gather the data. Using technology to gather and present the data increases students motivation throughout this investigation. In the term introduction phase, students used their data to construct a meaningful concept. This is achieved by a series of questions that compared the characteristics of the planets. The students use these characteristics to group the planets into two categories: terrestrial and Jovian. The concept application phase of the learning cycle allows students to expand on the original concept by comparing the compositions of the planets to the compositions of the other bodies in our solar system. Finally, students understanding of the concept was assessed as they addressed a recent controversy about the classification of Pluto. The activity correlates with the National Science Education Standards, a major theme of which is learning science is something that students do, not something that is done to them (National Research Council, 1996). This activity allows students to model research scientists. Students observe, question, gather, interpret, and analyze data to draw scientific conclusions. After completing the learning cycle, my students had a new appreciation for our solar system. More importantly, weeks later they were able to successfully apply their knowledge about this topic as they compared the composition of the planets to that of the Sun. Their success can be credited to the fact that students rely heavily on the application of their data. Changing this activity from a traditional research report to a learning cycle investigation provides students with the opportunity to do science. Jeffery Patterson (e-mail: jefferyp@norman.k12.ok.us) teaches science at Norman High School, 911 W. Main, Norman, OK 73069; and Brandy J. Merwin (e-mail: brandymerwin@worldnet.att.net) teaches science at Putnam City West High School, 8500 N.W. 23rd Street, Oklahoma City, OK 73127. References Marek, E.A., and A.M.L. Cavallo 1997. The Learning Cycle: Elementary School Science and Beyond. Portsmouth, N.H.: Heinemann. National Research Council. 1996. National Science Education Standards. Washington, D.C.: National Academy Press. Svitil, K. 2001. One of our planets is missing. Discover 22 (10). 26 The Science Teacher