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This activity gives students an opportunity to learn about the elements created in the cores of high-mass stars by fusion reactions. They will discover that all stars start by burning hydrogen and end up creating many heavier elements inside their cores, elements that will be released into space when it dies in a supernova explosion. Students associate a layer with an element that is being produced by the high-mass star. This will illustrate that as the temperature of the star increases with depth, the ash of each burning stage becomes the fuel for the next stage. Surrounding the core of iron nuclei is a layer of silicon fusion, then magnesium, then neon, then oxygen, then carbon, then helium, and lastly, in the relatively cool periphery of the core, hydrogen fuses into helium. Students will draw their own version of the onion-like nature of the core of a star based on the model and explain the process that occurs at each layer.
Summary
| Subject keyword(s) | Astronomy, Atoms, Chemical reactions, Chemistry, Earth science, Elements, Energy, Energy transformation, Fusion, Geoscience, Nuclear reactions, Physical science, Physical sciences, Physics, Science, Space science, Space Science, Space sciences, Structure of matter, Subatomic particles |
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| Grade level | High School, Vocational/Professional Development Education |
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| Intended audience | Educator |
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| Resource type | Instructional Material |
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| Resource format | text, text/html |
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| Rights | If using the HEASARC service made a significant contribution to a research project, please make the following acknowledgement in any resulting publication: This research has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), provided by NASAs Goddard Space Flight Center. Please send a preprint or reprint of the paper to: The HEASARC Code 660.2 NASA/Goddard Space Flight Center Greenbelt, Maryland, 20771, USA |
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Content contained within the resource
What's New Site Map NASA Homepage Search: HOME Science Special Exhibit Satellites and Data Teachers' Corner Ask an Astrophysicist Dictionary Resources Feedback Imagine Home | Teachers' Corner | Lesson Plans | Current page Activity - Fusion ReactionsDays Needed 1-2 Grade Level 11 - 12 Objective Students will learn about the elements created in the cores of high-mass stars in this activity. Science and Math Standards NSES Content Standard B: - Structure of Atoms - Interactions of energy and matter Content Standard G: - Nature of Scientific Knowledge Pre-requisitesStudents should be familiar with basic chemistry. Students should also have read the background sections on the Life Cycles of the Stars and the Dispersion of Elements. IntroductionElements are produced in the cores of high-mass stars by fusion reactions.All stars start by burning hydrogen and end up creating many heavierelements inside their cores. It is thiskind of star that will eventually spread the elements it created in itscore when it dies in a supernova explosion. Engagement Using colored clay, either home-made or store-bought, make a model of the core of a star. If time allows, the class can do this themselves,otherwise, the teacher can demonstrate it for the class. Materials: 8 colors of clay, either home-made or store-bought (see recipe for home-made clay) ball-bearing or other small metallic ball (large silver beads would work) plastic knife Procedure: Cover the ball-bearing or bead with one color of clay - make the layer of clayat least half an inch thick. Use another color of clay to make a layerover the first. Do this until you have 8 layers of clay, each a differentcolor, each at least half an inch thick. Now, cut the ball in half tomake a cross section (you'll have to cut around the ball-bearing). Theinside shows the different layers present in the core of a high-mass star. Each of those layers of claybelongs to a different element. The ball-bearing is the iron core of the star. At the end of the day's activity, the class will come back to the modeland learn what the different layers are. Exploration Materials: Index cards with elements written on them. You'll need 4 hydrogen-1 (1H) 13 helium-4 (4He) 4 carbon-12 (12C) 1 magnesium-24 (24Mg) 4 oxygen-16 (16O) 1 sulphur-32 ( 32S) 1 neon-20 (20Ne) 1 silicon-28 (28Si) 2 nickel-56 (56Ni) 2 cobalt-56 (56Co) 2 iron-56 (56Fe) 2 iron-57 (57Fe) 2 iron-58 (58Fe) 1 iron-59 (59Fe) 3 neutrons (n) 4 positrons (e+) 2 neutrinos at least 7 energy Give each student an index card with an element written on it. Have the students move about the classroom and construct fusion reactions. Their goal is to form the reactions that create helium, carbon, magnesium, oxygen, sulphur, neon, nickel, cobalt, and 4 different isotopes of iron. The teacher should assist or give hints as necessary. The students should end up with the following fusion relationships: 4 (1H) ------> 4 He + 2 e+ + 2 neutrinos + energy 3 (4He) ------> 12C + energy 12C + 12C ------> 24Mg + energy 12C + 4 He ------> 16O + energy 16O + 16O ------> 32S + energy 16O + 4 He -----> 20Ne +energy 28Si + 7(4 He) ------> 56Ni + energy 56Ni ------> 56Co + e+ (postive Beta Decay) 56Co ------> 56Fe + e+ (positive Beta Decay) 56Fe + n ------> 57Fe 57Fe + n ------> 58Fe 58Fe + n ------> 59Fe When the students create a correct reaction, write it on the board -keep the reactions in the order they are in the table above. The orderis important. Adapting for class size: The number of cards handed out will vary depending on class size. If your class size is small, only do 2 or 3 reactions at a time, handingout only the cards with elements that are in those reactions. Justbe sure every student has a card. If your class size is large, do about half the reactions at a time, giving the students only thecards used in those reactions. If there are not enough cards to go around, give out extra energy cards. It is alright to have more than onestudent representing energy in a reaction. When the students are done,collect those cards and hand out the cards used in the rest of the fusionreactions and have the class form them. When the class is done forming reactions, have them examine the reactions and their order. They should see, that like high-mass stars, they have created heavy elements, even though they started with just hydrogen. A high-mass star converts its hydrogen to helium, helium to carbon, carbon to magnesium, carbon and helium tooxygen, oxygen to sulphur, oxygen and helium to neon, and silicon andhelium to nickel. The unstable isotope of nickel created undergoespostive beta decay and forms an isotope of cobalt that in turn decaysinto iron. Positive beta decay is when a proton becomes a neutron, anda positron is emitted. A high-mass star creates many unstable isotopes of ironand actually goes through a series of reactions that cause the star to make heavier and heavier nuclei of elements, all the way up to bismuth-209 - the heavest known nonradioactivenucleus. This process is the origin of the copper and silver in the coins in our pockets, the lead in our car batteries, and the gold in the rings on ourfingers! Now that the class is aware of the order in which the elements are created in a star, bring them back to the model of the core of the star from the beginningof class. The ball-bearing is the iron core of the star. The layers outsideit are where various nuclei fuse. Have the students associate a layerof clay with an element that is being produced by the high-mass star.This will illustrate that as the temperature of the star increases with depth, the ash of each burning stage becomes the fuel for the next stage. Surrounding thecore of iron nuclei is a layer of silicon fusion, then magnsium, thenneon, then oxygen, then carbon, then helium, and lastly, in therelatively cool periphery of the core, hydrogen fuses into helium.The core is enveloped by a layer of nonburning hydrogen. Have the class draw their own version of the onion-like nature of the core of astar based on the model and explain the process that occurs at eachlayer for homework. Here is an example: An example of a drawing depicting thelayers of elements in the core of a high-mass star Evaluation Have each group of students explain the reaction they have made and why they think it is correct. Their individual diagrams and explanations of thecore of a high-mass star may also be evaluated. Reference URLs: Element Production http://zebu.uoregon.edu/disted/ph123/l10.html http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html http://library.thinkquest.org/17940/texts/ppcno_cycles/ppcno_cycles.html http://csep10.phys.utk.edu/guidry/violence/supernovae.html http://zebu.uoregon.edu/~soper/Sun/fusion.html http://zebu.uoregon.edu/~soper/Sun/fusionsteps.html Reference Book: Astronomy Today, by Eric Chaisson and Steve McMillan. Back to the Main Spectra Unit Menu
