W.2 reading

W.2: Revised Model of Sound © 2019 PEER Physics W.2 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.2e CCCs – Indirectly studying a phenomenon with multiple senses: When a phenomenon involves small-scale mechanisms that we cannot directly see, we can explore it indirectly using our senses. In this activity you made observations and revised your model for sound by using both your sight and hearing. Models give us a mechanistic understanding of phenomena that we experience in our daily lives. A mechanistic understanding means that we are able to explain how something is happening, and in scientific models, mechanisms can be shown in a visual way. In this activity, you expanded your model for sound to include and represent the small-scale mechanisms that account for what causes us to hear different pitches and volumes. These are the two main properties of sound that we use in everyday life, and so it makes sense that they would be the first things we explain using the ideas in our scientific models. You investigated pitch and volume by performing experiments, collecting evidence, and identifying patterns by making scientific observations … but in this activity you made these observations using two of your five senses: hearing and sight. Remember that in science, the term “observation” doesn’t just mean the things we see with our eyes, but rather any kind of information about the world that we gather through our senses. You made observations using your hearing and sight, and both were important in different ways to improve your scientific model for sound. Scientific models explain the things we observe using ideas about measurable, small- scale mechanisms. In this activity, you used multiple senses and different objects (rulers and tuning forks) to indirectly study the phenomenon of sound, and you revised your model to account for differences in things you both saw and heard. Since the phenomenon of sound is created by air particles that we cannot see directly, your sense of sight was necessary to make observations of vibrating rulers. You listened to the different pitches the rulers produced and observed the ways they were vibrating. By combining your auditory and visual observations, you could revise your model of sound to include more details about air particles and how they vibrate differently in sound waves of different pitches. You then made observations of tuning forks, which were also vibrating and producing sounds of specific pitches, and related them to the rulers. In other words, Your revisions were focused on identifying and naming patterns within sound waves of different pitches and volumes. For

W.2: Revised Model of Sound © 2019 PEER Physics instance, through your observations of the vibrating rulers, you explored a relationship between how each ruler was vibrating and the pitch you could hear. You described this relationship by developing a new concept for your model of sound: frequency, which has to do with how much particles in a medium are vibrating. The concepts of amplitude and wavelength, which you also developed in this activity, describe relationships between things you hear and the way your model explains them. Wave concept Related to our perception of… Measured through a… Model-based reasoning Frequency Pitch Rate How frequently particles are vibrating back and forth in a sound wave Amplitude Volume Magnitude How dense and compressed with particles the disturbances in the sound wave are Wavelength Pitch Distance How far apart the disturbances in the sound wave are W.2f SEPs – Revising models to explain new patterns: Through experimentation and by using mathematical tools like graphs, scientists identify new patterns and either revise their prior models or create new models to account for those patterns. Your current model of sound includes ideas about different patterns in sound waves. In the previous activity, you developed and revised a model for sound movement that included ideas about how air particles move in a medium as . In this activity, you expanded your model for sound movement to describe different patterns that exist in the ways we hear sounds - pitch and volume. Remember that scientific models are tools that scientists can use to represent patterns in the phenomena they are studying. Now your model of sound can represent what is different about sound waves that have different pitches and volumes. Your model still uses ideas about the movement of the disturbance and air particles in the medium, but you are using these characteristics of your model to be able to account for a broader set of observations. Scientists commonly switch between using different kinds of representations for the same phenomenon. Scientific models are used to represent simplified (and usually visual) ways of thinking about a phenomenon, and sometimes a single scientific model can lead to different kinds of visual representations. It is common for scientists to develop different kinds of visual

W.2: Revised Model of Sound © 2019 PEER Physics a. In the time interval shown, how many wave cycles occurred in Sound A, Sound B, and Sound C? b. Indicate which sound (A, B, or C) from the picture corresponds with which ruler length. Describe your reasoning. 4. In your own words, how would you describe the importance of combining your observations from multiple senses in this activity? 5. How have you used senses other than sight and hearing to make observations in this course? 6. Reflect on the observations you made of the vibrating rulers. How did your observations help you think differently about frequency and how air particles move in sound waves? 7. Wavelength and frequency are both related to the pitches of the sounds we hear, but each of these concepts relate to a different property of a sound wave. a. How would you describe the differences between those properties, in words? b. How would you represent the differences in those properties, using a density diagram? c. Represent the same differences from “b”, but now using wave diagrams instead. 8. Do you think your sense of touch was in any way important during the experiments you conducted in this activity? Consider the ruler and tuning fork experiment in your response. 9. You have considered two different model-based representations for sound: density diagrams and wave diagrams. a. What are some of the benefits of each of these models? b. When might it be more useful to use a density diagram? c. When might it be more useful to use a wave diagram? 10. In what kind of situation would you prefer to use a density diagram to represent a sound wave? 11. In what kind of situation would you prefer to use a wave diagram to represent a sound wave? 12. Use ideas about air particles, frequency, amplitude to explain in your own words why some people might find it painful to hear sounds that have a high pitch , or a high volume .