W.1 reading

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Jan 9, 2024

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W.1: Model of Sound © 2023 PEER Physics W.1 N ATURE OF S CIENCE R EADING Instructions: The purpose of this Nature of Science reading is to contextualize and formalize the Crosscutting Concepts and Science Practices from this activity. Physics principles (Disciplinary Core Ideas) were formalized in the Scientist’s Ideas reading. These three pieces– Crosscutting Concepts (CCCs), Science Practices (SEPs), and Disciplinary Core Ideas (DCIs) - are often referred to as “the Three Dimensions” of science learning. As you read, consider the ways you engaged in and with the three dimensions throughout this activity. W.1f CCCs – Developing initial models using ideas about energy: Scientists commonly develop initial models of phenomena by applying ideas about energy and how it relates to the phenomenon. Developing a model of sound involves ideas about small-scale entities and mechanisms which cannot be studied directly. In this activity you began the process of developing and revising a model of sound . This process involved making observations of phenomena related to sound, identifying patterns in your observations, and using scientific ideas to develop explanations for those patterns. You have engaged in this process before, for example when investigating static and current electricity. Even though the phenomena of electricity and sound are different, there are parallels in the ways that scientists develop models to explain them. For instance, your models for static and current electricity involved ideas about small-scale entities and interactions that you could not directly observe, and the same thing is happening now that you are developing a model of sound. Since you could not directly see the small-scale entities that cause these phenomena, you needed to study them indirectly using tools like simulations, visualizations, and analogies. From these indirect observations, you developed initial models that you could build upon and revise as you gather new evidence. The table below contrasts some of the details and tools that you used when exploring phenomena of static electricity (in a previous chapter) and sound (this activity).

W.1: Model of Sound © 2023 PEER Physics Phenomenon (Activity) Small-scale entities Interactions Tools Static electricity in insulators (C.2) Positive and negative charges Attraction and repulsion Simulations Movement of sound from a sound source to a listener (W.1) Air particles in the medium Patterned movement of air particles and collisions Visualization and Newton’s cradle analogy Energy is often a very important crosscutting concept to include in models of phenomena. Energy is a concept that is extremely important for most models of natural phenomena, and in this activity you applied ideas about energy to your initial model of sound. Notice that doing this involves an assumption about the phenomenon of sound, an assumption that maybe you did not realize that you were making - that sound can be thought of as some kind of energy. Scientists call this sound energy , but you began developing a model of sound by first thinking of another kind of energy, the energy involved in movement. In the Initial Ideas, when you observed the movement of a candle flame and developed an initial hypothesis about what might be causing this movement, you were indirectly studying air particles and starting to include energy ideas into your model. Your hypotheses involved ideas about waves, or maybe air particles, that were themselves moving and interacting with the candle flame in some way. In other words, your initial hypotheses were already trying to explain where the candle’s movement energy came from, and how that energy arrived at the candle flame.

W.1: Model of Sound © 2023 PEER Physics Your investigations throughout this activity were designed to support you in revising your model of sound to better explain how sound energy moves from place to place. Each investigation you conducted, and each tool you used to indirectly study how air particles move and interact with each other, gave you new kinds of evidence to add to your model. For instance, the air particle visualization showed you how individual air particles have a patterned, back-and-forth movement, even though disturbances in the medium continue moving from the sound source to the listener. Your exploration of the Newton’s cradle analogy focused your attention on how individual air particles in a medium can transfer movement energy, through their own movement and collisions with each other. Due to this process, disturbances in the medium can travel from the sound source to a listener, even while each individual air particle is only moving a short distance. Your current model of sound combines your observations and inferences from all these different explorations, and can now explain how small-scale interactions between particles transport sound energy from place to place. W.1g SEPs – Revising an initial model to include new observations: When developing a model for a new phenomenon, scientists always reflect on how their observations can lead to some kind of model revision or improvement. Developing an initial model for a phenomenon involves a process of collecting data and reflecting on how that data can be incorporated into the model. Scientists always think of the models they create as being open to revision and change, especially when they make new observations, or collect new data, that their models do not account for. This is true of all models, regardless of whether they are in an initial or revised state. In this activity you probably revised your model of sound to account for new observations. For instance, after observing the candle flame, your initial model might have included ideas about how air particles moved outward from the speaker and passed through the candle flame. Since you could not see the air particles directly, this explanation for why the candle flame moved accounted for the observation you made. Later, when you observed the air particle visualization and interacted with the Newton’s cradle, you collected new data that may have led you to revise the ideas in your initial model. The air particle visualization showed you that air particles do not move all the way from a sound source to a listener, but actually have a patterned and repetitive back-and-forth movement. That same visualization showed you that a disturbance in the medium does move all the way from the sound source to the listener, and by observing the Newton’s cradle, you could explain how this disturbance’s movement is related to how individual air particles collide and transfer energy to each other.

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W.1: Model of Sound © 2023 PEER Physics It is important to reflect on how the ideas in your initial model relate to the new observations you made throughout this activity. For example, if your initial model included ideas about air particles moving across the medium, your revised model now differentiates between the movement of air particles and the movement of the disturbance . Your initial ideas were not wrong, they were just built on limited evidence. By performing new experiments and making new observations, you increased the level of detail in your model, which in turn made it more useful and able to explain sound phenomena. W.1 3D Q UESTIONS Respond to the following questions individually in your lab notebook: 1. What is a “sound wave”? Explain in words and make a visual diagram that represents your thinking. 2. Why is it that you wouldn’t hear the sound of an explosion or someone talking to you in outer space? Use the term “medium” in your response. 3. How is it that sound can travel from a sound source to a listener without the air particles in the medium moving the same distance? Use your observations of the Newton’s cradle to support your thinking. 4. What are some characteristics of longitudinal waves ? 5. In this activity you made observations of a Newton’s cradle. In what way(s) did your observations support or change the ways in which you thought about air particles in your model of sound? 6. What do you think are some limitations , or oversimplifications , of the Newton’s cradle analogy? 7. Revisit your Initial Ideas from when you first observed the candle flame. How is your current model of sound similar and different from your Initial Ideas? Consider how you were thinking of energy and the movement of air particles then, and how you think of these concepts now. 8. At this point you have gone through the process of building and revising models for different kinds of phenomena. Choose one of the phenomena you have explored previously - static electricity, current electricity, or magnetism - and reflect on the parallels between how this process looked and felt like for that phenomenon , in comparison with the phenomenon of sound.

W.1: Model of Sound © 2023 PEER Physics 9. Also thinking back to the many models you’ve built in the course (considering static electricity, current electricity, magnetism, and sound waves), reflect on one occasion when you had to revise your model using new evidence. a. Describe what your initial model was like. b. Describe some evidence that required you to revise your model. c. Describe how you revised your model to account for the new evidence. d. Looking back at this process of model revision, would you describe the initial model you revised as “wrong”, incomplete, or something else? Describe your reasoning. e. Have your feelings about revising scientific models changed in any way over time? Why or why not? 10. In your current model of sound, what is the difference between the movement of the disturbance and the movement of air particles ? Do you think of these concepts as being related to each other in some way? 11. Choose one of the experiments you conducted in this activity. How did that experiment provide you with new observations to incorporate into your model of sound? 12. Why do you think ideas about energy are important when developing a model for a phenomenon?

W.1 reading

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