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Background Information
The Tracing Origins activity is the first in a series of three “Thought Experiments.” Scientists use thought experiments when it is not possible to actually conduct real experiments with real equipment. In this activity, students are encouraged to act both as cosmologists and cosmogonists as they make observations regarding the structure of a pizza and in “Tracing the origins of pizza ingredients” back to atoms, the building blocks of matter.
But atoms have their own building blocks—protons, neutrons, and electrons, which leads students to ask questions that lead into Activity 2, The Fundamentals of Our Universe.
Students will use this “tracing process” again in Activity 3 as they trace quarks and electrons backwards in time to discover what important role these fundamental particles may have played in those early cosmic periods when the universe was in a state of high density and high energy.
| National Science Education Standards Addressed |
| Grades 5–8 |
| Science As Inquiry |
- Understands about scientific inquiry
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| Physical Science |
- Properties and changes of properties in matter
- Transfer of energy
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Science and Technology
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- Understandings about science and technology
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| History and Nature of Science |
- Nature of science and scientific knowledge
- History of science and historical perspective
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| Grades 9-12 Science As Inquiry |
- Understands about scientific inquiry
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| Earth and Space Science |
- The origin and evolution of the universe
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| Physical Science |
- Structure of atoms
- Motions and forces
- Interactions of energy and matter
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| Science and Technology |
- Understandings about science and technology
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| History and Nature of Science |
- Nature of science and scientific knowledge
- History of science and historical perspective
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| (View the full text of the National Science Education Standards.) |
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| Materials |
- One or more baked pizzas, depending upon the size of your class. You should have enough pizzas so that each student can have a slice to observe. If you need more than one pizza, however, they should all have the same toppings.
- One unbaked pizza with identical toppings for students who have never “seen” one so that they can observe the differences between baked and unbaked pizza.
- Paper towels or napkins
- Plastic gloves so students can feel the whole pizza that represents space as a whole
Optional:
- Copies of the Student Activity, “Tracing the Origins Pizza Ingredients” in the appropriate format for each student. Student Text materials are available for use with audio-amplified computer software, bold 18-point font print copy for partially sighted students, and in Braille for significantly sight-impaired students. You may select the most appropriate version of these materials by following these directions.
Background
for tracing the origins of pizza ingredients |
In this activity, students will go back in time to “visualize” how a pizza “came to be.” This activity will introduce to students to a process that scientists use to “trace” known components of today’s universe “back to the beginning.”
As you prepare for this activity, you need to consider
the origin of the ingredients of the pizza that you will use in
the classroom. For example, all pizza crusts are formed from flour,
which came from wheat berries (seeds), which came from wheat plants,
which are mostly cellulose and other
polysaccharides made of molecules made of carbon, hydrogen, and
oxygen atoms. In the same way, the cheese, tomato sauce, meats and
other ingredients of the pizza can be traced back to atoms of their
elemental constituents. Carbohydrates and fats can be traced back
to carbon, hydrogen, and oxygen atoms. Proteins are made of carbon,
hydrogen, oxygen and nitrogen atoms. Atoms are the building blocks
of matter.
Tracing the origins of pizza ingredients back to the types of atoms they are made of should lead to questions like:
- Where did the atoms of these elements come from? They come from water, air, and soil of the Earth.
- How did these elements get into
 the matter from which Earth and its environment were formed? Most of the matter on Earth, even the common pizza, consists of atoms that were formed inside stars and were distributed through space in earlier supernova explosions.
Procedure |
- Ask students whether any of them or their parents have traced their genealogies, their family histories. How far back could they go? Great grand parents? Farther back than that? Did they learn anything interesting about their family histories? Why do you think that we are interested in finding out where we came from?
 When you have exhausted student responses, tell students that they are going to trace the genealogy of a pizza. Distribute copies of the Tracing the Origins of Pizza Ingredients Student Activity in the appropriate forms to each student.- Have them put
on their gloves. First, they will “observe” the whole,
unbaked pizza. Have the students make observations about an unbaked
pizza with ingredients that are identical to the baked one they
will observe later. Students who have no sight will observe the
pizza tactilely. Those with limited sight should also be encouraged
to observe visually.
- Then have students observe a baked pizza. Have students make comparisons between the unbaked and baked pizzas. Ask questions like:
- How is the cheese different before and after baking?
- How does the crust feel (look) different before and baking?
- Ask sighted students what differences
in color they observed between the baked and unbaked pizza.
Student observations will depend upon what kind of pizza you have furnished. You may have students keep a list—either in braille or handwritten—of their observations for future reference on the Student Activity Sheet. Another option is for you to make the list and keep it available for student reference.
- Then give each student a piece of the baked pizza that they have just observed. You may also choose to continue to make the unbaked pizza available for further observation. Give students time to work on the five questions on the student activity sheet.
- If students do not finish during the class period, this could be a homework assignment for the next class period. Make sure that students understand the meaning of “trace” in question 6 on the student activity sheet. “Trace” here means that we are going back in time, to see what the ingredients looked back before they were pizza ingredients, not “tracing something with an instrument.” Guide them as they trace the ingredients back to the “ atom” level.
- When students have finished the student activity, continue with a classroom discussion in which your students consider answers to the questions below. They are designed to give students a different perspective of the universe and that add to their understanding of the structure of the universe. Ask questions like:
| - Are pizzas made up of only one kind of matter? Is the universe made up of only one kind of matter?
- What different ingredients (or parts) of the whole pizza can you identify? How are the different ingredients similar to the different cosmic structures in the universe?
- Do all of your pieces have some crust? What is crust made from? What is flour made from? Continue to ask questions like this until you reach the level of atoms. (See the Background Information above.) You may wish to ask students how far back they traced the other ingredients as they completed their worksheets. [Since all matter is made of atoms, all the topping ingredients could be traced back to atoms.]
- Some ingredients are found throughout the pizza; others are isolated. How is this like the universe?
- Do all the ingredients of the pizza have the same density? How is this like the “ingredients” of the universe?
 Did
each of you have all of these ingredients in your slice of the
pizza? Why or why not?- Do each of your have the same amount of each ingredient in your slice? Why or why not?
- How is observing an individual piece of pizza different from observing the whole pizza? How is observing a piece of the pizza like studying a “piece” of the universe?
- Was it was easier to observe a piece of the pizza or the whole pizza? How is this like the universe?
- If there are bubbles in the crust (or in the cheese), ask what caused the bubbles? If students answer HEAT causes carbon dioxide gas produced by yeast to expand, ask: “How are the bubbles in the pizza like Hubble bubbles in the universe? Are they formed in the same way?”
- If you let students eat the pizza, ask whether there were things that they could taste even if you couldn’t observe them using touch or sight. Some ingredients, like garlic or spices, can be tasted but not seen or felt. How is this like the universe?
- Keep probing with questions like:
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- Where did the atoms that make up the pizza come from? [The water, air, and soil of the Earth.]
- Did anyone trace back further than atoms? If so (or if not), what are atoms made of? [protons, neutrons, and electrons]
- Does anyone know where protons, neutrons, and electrons came from? If not, then maybe, we need to explore the origins of pizza ingredients a little further.
- What previous knowledge did you use as you traced your ingredient back to its “origins”?
- Conclude this activity by telling students that they have been using the same thought processes cosmologists and cosmogonists do as they observe the universe as it is today and think about what the universe looked like as it was developing. Scientists use modeling and thought experiments when it is not possible to actually conduct real experiments with real equipment.
Clarify the difference between cosmologists and cosmogonists. Cosmologist are scientists who study the structure and changes in the present universe in order to predict the future of the universe while cosmogonists are scientists concerned with the origin of the universe. Practically speaking, the work of these scientists overlaps. Observations about the structure and changes in our present universe may not only allow predictions to be made about the future, but they also have provided clues to events that happened long ago when the chemical evolution of the cosmos began.
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| Citations |
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1. Coming of Age in the Milky Way, Timothy Ferris, William Morris
and Company, Inc., New York, 1988.
2. Bright Galaxies, Dark Matters, Vera Rubin, American Institute
of Physics Press, Woodbury, NY, 1997.
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