What Makes Things Float?

Transcription

1 What Makes Things Float? An Immersion Unit Investigating Density and Buoyancy 8th Grade Physical Science Immersion Unit June 2006 DRAFT 2

2 Buoyancy and Density: What Makes Things Float? This Grade 8 Immersion Unit is being developed in partnership with the Los Angeles Unified School District and is being tested and revised by teachers, scientists, and curriculum developers associated with the NSF-funded Math/Science Partnership, System-wide Change for All Learners and Educators (SCALE) and the DOE-funded Quality Educator Development (QED) project at the California State University Dominguez Hills. Immersion Units provide a coherent series of lessons designed to guide students in developing deep conceptual understanding that is aligned with the standards and key concepts in science. In Immersion Units, students learn academic content by working like scientists: making observations, asking questions, doing further investigations to explore and explain natural phenomena, and communicating their results based on evidence.

3 Table of Contents Navigating the Unit...7 Unit Overview...9 Unit Overarching Concepts...9 Unit Supporting Concepts...9 Evidence of Student Understanding...9 Unit Preview...9 Unit Standards...10 Unit Timeline...11 Unit Content Background...13 Unit Investigation...13 What Makes Things Float? Unit Level Graphic Organizer...13 What Makes Things Float? Chart...14 Support Materials...16 Step 1 Overview...19 Step 1 Lesson 1 Snapshot: Floating Puzzles...21 Teacher Background Information...23 Implementation Guide...27 Student Page 1.1A: Floating Puzzles...29 Step 1 Lesson 2 Snapshot: Crafting Testable Questions...31 Teacher Background Information...33 Implementation Guide...34 Student Page 1.2A: Questions for Investigations...35 Teacher Page 1.2a: Questions for Investigations...37 Step 2 Overview...39 Step 2 Lesson 1 Snapshot: Mass and Floating...41 Teacher Background Information...43 Advance Preparation...43 Implementation Guide...44 Student Page 2.1A: What Makes Things Float?...47 Step 2 Lesson 2 Snapshot: How Heavy?...49 Teacher Background Information...51 Advance Preparation...52 Implementation Guide...53 Table of Contents

4 Step 2 Lesson 3 Snapshot: Analyzing Data to Predict What Will Float...55 Teacher Background Information...57 Advance Preparation...57 Implementation Guide...58 Student Page 2.3A: Graphing Results...61 Student Page 2.3B: Interpreting Data...63 Teacher Page 2.3c: Think Aloud Notes for Analyzing Results...65 Step 2 Lesson 4 Snapshot: Density Defined...67 Implementation Guide...69 Student Page 2.4A: What is Density?...71 Step 2 Lesson 5 Snapshot: Milestone Challenge #1: Using What We Know about Floating and Sinking...73 Advance Preparation...75 Implementation Guide...76 Student Page 2.5A: What Does Density Have To Do With Floating?...77 Teacher Page 2.5a: What Does Density Have To Do With Floating?...79 Step 3 Overview...81 Step 3 Lesson 1 Snapshot: Displacement in a Liquid...83 Advance Preparation...85 Implementation Guide...86 Student Page 3.1A: Displacement in a Liquid...89 Student Page 3.1A: Displacement in a Liquid (continued)...91 Student Page 3.1A: Displacement in a Liquid (continued)...93 Teacher Page 3.1a: Displacement in a Liquid...95 Step 3 Lesson 2 Snapshot: Milestone Challenge #2 Which Medal?...97 Implementation Guide...99 Student Page 3.2A: Milestone Challenge #2 Which Medal? Step 4 Overview: Buoyancy and Forces Step 4 Lesson 1 Snapshot: Exploring Apparent Weight and Buoyancy Teacher Background Information Advance Preparation Implementation Guide Student Page 4.1A: Drawing Forces Student Page 4.1A: Drawing Forces (continued) Student Page 4.1B: Archimedes Investigations Student Page 4.1B: Archimedes Investigations (continued) Teacher Page 4.1a: Forces Step 4 Lesson 2 Snapshot: A Balance of Forces Teacher Background Information Implementation Guide Student Page 4.2A: A Balance of Forces Student Page 4.2A: A Balance of Forces (continued) Buoyancy and Density: What Makes Things Float?

5 Student Page 4.2B: Remembering Archimedes Teacher Page 4.2a: A Balance of Forces Step 4 Lesson 3 Snapshot: Predicting Payload Teacher Background Information Advance Preparation Implementation Guide Student Page 4.3A: Milestone Challenge #3 Predicting Payload Step 5 Overview: Fluids and Buoyancy Step 5 Lesson 1 Snapshot: Liquids and Buoyancy Teacher Background Information Advance Preparation Implementation Guide Student Page 5.1A: Liquids and Buoyancy Teacher Page 5.1a: Liquids and Buoyancy Teacher Page 5.1b: Density Table Step 5 Lesson 2 Snapshot: Gases and Buoyancy Teacher Background Information Implementation Guide Student Page 5.2A: Gases in the Ocean Student Page 5.2A: Gases in the Ocean (continued) Teacher Page 5.2a: Gases in the Ocean Teacher Page 5.2a: Gases in the Ocean (continued) Teacher Page 5.2a: Gases in the Ocean (continued) Step 6 Overview: Unit Evaluation Step 6 Lesson 1 Snapshot: Density and Buoyancy Misconceptions: Oil Spill Implementation Guide Student Page 6.1A: The Exxon Valdez Student Page 6.1A: The Exxon Valdez (continued) Step 6 Lesson 2 Snapshot: Inquiry into Density and Buoyancy Student Page 6.2A: Scientific Investigation Table of Contents

6 6 Buoyancy and Density: What Makes Things Float?

7 Navigating the Unit This Immersion Unit provides a coherent series of lessons designed to guide students in developing deep conceptual understanding that is aligned with the standards, key science concepts, and essential features of classroom inquiry (as defined by the National Science Education Standards). In Immersion Units, students learn academic content by working like scientists: making observations, asking questions, doing further investigations to explore and explain natural phenomena, and communicating results based on evidence. Immersion Units are intended to support teachers in building a learning culture in their classrooms to sustain students enthusiasm for engaging in scientific habits of thinking while learning rigorous science content. This Immersion Unit is comprised of several steps; each step contains between one and four lessons. The unit begins with the Unit Overview, which includes a description of the key concepts, evidence for student understanding, assessment strategies and other relevant implementation information. The Unit Overview outlines the conceptual flow and rationale for the structure of the unit. Each step in the unit begins with an overview, which describes the individual goals and activities of the specific step, and its relationship to the previous and following steps. The title and approximate length of time needed for each lesson is also shown. Within the step, each lesson contains: Snapshot Background Information Implementation Guide Student Pages Teacher Pages Snapshots are printed on a single page and provide key information for implementing the lesson. Each snapshot includes the key concept(s), evidence of student understanding, list of materials, procedures for lesson implementation, key words and REAPS a strategy for assessing student learning. This page is designed to have on hand while you implement the lesson. The Background Information and Implementation Guide sections provide learning experiences such as investigations, reading research, or other engaging supporting strategies designed to teach a specific concept(s). They include instructions for any advance preparation required, explain the design of the lesson, include strategies for assessing student learning, and provide teacher background information on relevant science content. The Implementation Guide for each lesson addresses teaching methodology, including specific examples and information related to effective teacher implementation. If research identifies common misconceptions related to the content, a detailed explanation of common misconceptions is provided with suggestions for addressing them. Student pages may include readings, guides, handouts, maps or instructions to engage students during the lesson. These pages assist you as you guide students through the lesson, and are intended to be readily adapted to suit a variety of classrooms with diverse student populations. Teacher pages may include overheads, maps, data charts and other materials that can help you implement the lesson. (continued on following page) Snapshot Page The information on the Snapshot page includes the following: Lesson Title Materials Key Concept Key Words Time Needed REAPS Questions Unit Overview 7

8 This Immersion Unit contains a variety of opportunities for modifying content and methodology based on your students needs and your classroom situation. The basic structure of the unit is designed to support you in anticipating the particular needs of your students to foster understanding of inquiry, nurture classroom communities of science learners, and engage students in learning key science concepts. 8 Buoyancy and Density: What Makes Things Float?

9 Unit Overarching Concepts Density is the relationship between mass and volume and is an intrinsic property of materials under stable conditions. Whether an object will float or sink can be predicted by comparing the object s density to the density of the fluid in which the object is immersed. Science knowledge advances through inquiry. Unit Supporting Concepts The density of an object can be calculated from measurements of mass and volume taken from the object. The volume of an irregular solid can be measured using water displacement. Equal volumes of different substances usually have different weights. Buoyancy is a balance between the gravitational force and buoyant force. Scientists differ greatly in what phenomena they study and how they go about their work. Although there is no fixed set of steps that all scientists follow, scientific investigations usually involve the collection of relevant evidence, the use of logical reasoning, and the application of imagination in devising hypotheses and explanations to make sense of the collected evidence (Benchmarks quote). Evidence of Student Understanding By the end of this unit, the student will be able to: demonstrate that density is a physical property of an object and is independent of the amount of substance being examined explain graphically and orally that the ratio of an object s mass to volume is its density calculate the density of a an object from measurements of mass and volume taken from the object explain that the buoyant force acting on an object that is immersed in a fluid is an upward force equal to the weight of the fluid displaced by the object analyze and correct the explanation in a real-life scenario to accurately reflect the scientific understanding that the buoyant force acting on an object opposes the force of gravity acting on the object and the magnitude of the buoyant force depends on the difference between the object s density and the density of the fluid in which the object is immersed use an appropriate combination of evidence to predict whether an object will float or sink by comparing the object s density to the density of the fluid in which the object is immersed identify and engage in all aspects of scientific inquiry. explain how studying natural phenomena through scientific inquiry advances knowledge. construct appropriate graphs from data and develop qualitative statements about the relationships between variables. Unit Preview What makes things float? This simple question opens the door to several fundamental concepts in the physical sciences, including how density and a balance of forces determine whether an object will float. These concepts are directly observable and can easily be investigated by 8th grade students. In this unit, students begin by exploring the overarching question, What makes things float? through a series of observations and questions about odd pairs of floating and sinking objects. The unit continues through a series of three steps in which students engage in short investigations to explain the Unit Overview 9

10 Unit Standards Density and Buoyancy All objects experience a buoyant force when immersed in a fluid. As a basis for understanding this concept: a) Students know density is mass per unit volume. b) Students know how to calculate the density of substances (regular and irregular solids and liquids) from measurements of mass and volume. c) Students know the buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced. d) Students know how to predict whether an object will float or sink. Forces Unbalanced forces cause changes in velocity. As a basis for understanding this concept: a) Students know a force has both direction and magnitude. b) Students know when an object is subject to two or more forces at once, the result is the cumulative effect of all the forces. c) Students know when the forces on an object are balanced; the motion of the object does not change. d) Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction).e) f) Students know the greater the mass of an object, the more force is needed to achieve the same rate of change in motion. Investigation and Experimentation Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students will develop their own questions and perform investigations. Students will: a) Plan and conduct a scientific investigation to test a hypothesis. b) Evaluate the accuracy and reproducibility of data. c) Distinguish between variable and controlled parameters in a test. d) Recognize the slope of the linear graph as the constant in the relationship e) y = kx and apply this principle in interpreting graphs constructed from data. f) Construct appropriate graphs from data and develop quantitative statements about the relationships between variables. g) Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed = distance/time, density = mass/volume, force = pressure area, volume = area height). h) Distinguish between linear and nonlinear relationships on a graph of data. 10 Buoyancy and Density: What Makes Things Float?

11 factors that determine whether an object will sink or float. In Step 5, students are introduced to density and buoyancy in liquids and gases and the effect that temperature has on these properties. In the final step, students apply what they have learned about those factors to interpret how density and buoyancy played a role in the oil spill that followed the grounding of the Exxon Valdez tanker, a widely publicized event from As students work through the basic principles outlined in the overarching and supporting concepts through direct observation, testing, and measurement, they develop an enduring understanding of density and buoyancy and the ability to apply what they learn to solve problems. Unit Timeline Step Lesson Step 1 Step 1 Lesson 1 Floating Puzzles Step 1 Lesson 2 Crafting Testable Questions Step 2 Step 2 Lesson 1 Mass and Floating Step 2 Lesson 2 Floating Data Step 2 Lesson 3 Analyzing Floating Data Step 2 Lesson 4 Defining Density Step 2 Lesson 5 Challenge #1 Density Class Time 50 min 50 min 50 min 50 min 50 min 50 min 50 min Key Concepts Scientists observe natural phenomena, pose questions, and wonder based on their observations. Scientists observe natural phenomena and develop testable questions based on their observations. Scientists use precise measurements to make accurate explanations. Heavier cubes are more likely to sink than lighter cubes (of equal volume). Two different-sized objects made of the same material sink or float the same way. Heavy things may float or sink depending on their size. Objects with a density less than the density of water (1 g/cm3) will float in water at some level. Under stable conditions, the density of a substance is a standard property of that substance and does not change. Objects with a density less than the density of water (1 g/cm3) will float in water at some level. Under stable conditions, the density of a substance is a standard property of that substance and does not change. Objects with a density less than the density of water (1g/cm3) will float in water at some level. Unit Overview 11

12 Step Lesson Step 3 Step 3 Lesson 1 Displacement of Liquids Step 3 Lesson 2 Challenge #2 Irregular Shapes Step 4 Step 4 Lesson 1 Exploring Apparent Weight & Buoyancy Step 4 Lesson 2 A Balance of Forces Step 4 Lesson 3 Predicting Payloads Step 5 Step 5 Lesson 1 Liquids and Buoyancy Step 5 Lesson 2 Gases and Buoyancy Step 6 Step 6 Lesson 1 Evaluation: Misconceptions and Oil Spills Step 6 Lesson 2 Inquiry into Density and Buoyancy Class Time 50 min 50 min 50 min 50 min 50 min 50 min 50 min 50 min 50 min Key Concepts When an object is fully submerged it displaces a volume of liquid equal to its own volume. When an object is partially submerged it displaces a volume of liquid equal to the volume of the portion of the object that is submerged. Scientists use multiple methods to calculate volume. When an object is fully submerged, it displaces a volume of liquid equal to its own volume. Under stable conditions, the density of a substance is a standard property of that substance and does not change. Gravity pulls down on all objects and accelerates them at a rate of 9.81 m/s2. The buoyant force pushes up on all objects and depends on the submerged volume of the object. Objects float if the buoyant force is larger than the gravitational force and sink if the gravitational force is larger than the buoyant force. Buoyancy is determined by differences between the gravitational force and the buoyant force. Materials more dense than the liquid they are submerged in can still float, just use balance of forces in design The density of liquids affects the buoyancy of objects submerged in those liquids. Temperature affects the density of fluids. The principles of density apply to gases as well as to liquids, and it affects the buoyancy of objects in those gases. Density and a balance of forces determine whether or not an object will float. Common misconceptions can be addressed using evidence-based explanations. Scientific investigations are usually directed by a specific testable question and involve collecting relevant evidence and using logical reasoning to develop evidence-based explanations. 12 Buoyancy and Density: What Makes Things Float?

13 Unit Content Background Whether drinking from a glass of iced tea, swimming in a pool, boating on a lake, or studying the surface of Earth itself, the concepts of buoyancy and density permeate everyday life. Density, a measurement of the amount of matter contained in a given space, is an intrinsic property of materials under stable conditions and is a large part of the solution to figuring out whether things float or sink. Buoyancy, a balance of forces between the weight of objects and pressure from a surrounding fluid, factors into the rest of the explanation for floating or sinking objects. Taken together, the two concepts explain everyday occurrences like why ice, (most) people, and boats float on water and why Earth s crust is made the way it is with rocks of a certain density, less than that of other parts of the interior of Earth. There are many common misconceptions about buoyancy and density. These include ideas such as all wood floats, heavy objects always sink, and others about related concepts of forces and properties of materials that determine whether they float or sink. Throughout this unit, there are opportunities for students to test their conceptions of density and buoyancy and confirm or refute their ideas through investigation and experimentation. Unit Investigation This unit s investigation involves a series of studentdirected inquiries that take place over the course of the unit to answer the question, What makes things float? Students begin the unit by developing and then refining questions after observing sets of discrepant events involving density and buoyancy. These student-developed questions are systematically referenced after each mini-inquiry into the properties that affect density and buoyancy. In this way, students can evaluate evidence gathered in light of possible explanations for their questions while developing a way of knowing how to decide what makes things float. What Makes Things Float? Unit Level Graphic Organizer Many lines of evidence work together to explain what determines whether an object will float or sink in a particular fluid under particular conditions. This unit uses a graphic organizer to help students visualize how all this evidence fits together. The What Makes Things Float? graphic organizer is used throughout the unit, and evolves as students gather more evidence that supports understanding of buoyancy and density. The example on the following page shows how the Unit Level Graphic Organizer may look at the end of this unit. (Note: For each lesson that references the chart, there is an example chart in the Implementation Guide that illustrates how it may look at that specific point in the unit.) Unit Overview 13

14 What Makes Things Float? Chart What did we do in this lesson? What evidence did we collect? Big idea(s) I took away from the lesson How would you use that evidence to make a prediction? Measured mass of and floated cubes Mass of the cubes and whether they floated Heavy things sink, light things float It is not true that All wood floats or All plastics float Weigh an object before predicting Measured mass of different cube combinations and floated them Mass of cube combinations and whether they floated Measuring mass or weight doesn t seem to be quite enough information to always predict correctly whether a group of cubes will float. Not sure. We need to know more to always make accurate predictions. It is harder to predict if combinations of cubes will float than to predict if a single cube will float. Rate of sinking can be changed because cube combinations sink at different rates. Plotted data points on a graph of mass and volume For everyone in the class, cubes sank when they were above a certain space on the graph and floated when they were below it. There are patterns in the graph of our class data that may help to predict if something will sink or float Analyzed plotted data points on a graph of mass and volume The mass-to-volume ratio of objects that sink in water is greater than the density of water. Measuring and calculating the ratio of mass to volume for an object makes it easy to predict if the object will sink or float in water. Observed and measured the amount of overflow fluid from the container Volume of overflow fluid Objects that sink raise the fluid level in their container One way to find the volume of an irregularly-shaped object is to measure the volume of fluid it displaces Not sure. Volume is related to density but it alone cannot be used to predict whether an object floats. 14 Buoyancy and Density: What Makes Things Float?

15 Felt the forces needed to sink floating cubes and ping-pong balls Qualitative measurement of forces Ping-pong balls push back with a greater force than floating cubes when you hold them under water. Not sure. Knowing the amount of push-back force may help predict if an object will float. Used a spring scale to measure the weight of objects in water and air Weight of objects in water and air Sinking objects must have an upward force on them that makes them appear to weigh less in water than in air Different liquids and gases seem to push back in different ways. Objects that sink weigh less in water than they do in air Observed objects floating on the surface of liquids Whether objects float or sink in liquids There is a balance of forces on floating objects Floating objects remain at rest where they float Not sure. The liquid has something to do with whether objects float. Observed oil and water together in one container Oil floats in water Liquids can have different densities, not just solids Measuring the density of a liquid helps predict if it will float on another liquid. Analyzed plotted data points on a graph of mass and volume (density) Liquids can have different densities, not just solids The mass-to-volume ratio of liquids that float (or sink) in other liquids is greater than (or less than) the m/v ratio of the other liquids If you are working with a pure liquid (or solid or gas), it is possible to know what the density is by looking it up or measuring it just once, because it is a property that stays the same for a pure substance. Read a story about methane gas in the ocean The density of gases like methane and air Gases can have different densities too! Gas bubbles rise in liquids Gases that are less dense than the fluid they are in will always float. The same gas can have different densities depending on the temperature Hot air rises because it is less dense than cooler air. Unit Overview 15

16 Support Materials Immersion Unit Toolbox and CD The Immersion Unit Toolbox is central to this curriculum. It is a separate guidebook that discusses the concepts inherent in teaching science through immersion units. These concepts include engaging in scientifically oriented questions, giving priority to evidence in responding to questions, and formulating explanations from evidence. The Toolbox also describes several pedagogical approaches (Think-Aloud strategies, for example) that are key to how these units work. Most of the strategies in the Immersion Unit Toolbox support student engagement in scientific inquiry based on the Five Essential Features of Classroom Inquiry (NRC, 2000). Before you use What Makes Things Float? in your classroom, it is recommended you become familiar with the strategies addressed in the Immersion Unit Toolbox. This Immersion Unit comes with a data CD containing multimedia files for use at various points throughout the unit. It also contains resources and links to reputable Web sites that students can use during their region investigation. A CD icon in this unit highlights the points where many of these materials are referenced in the lessons. Here is a brief overview of some of the strategies you can use in your classroom. Science Inquiry Map The Science Inquiry Map on the following page illustrates the Five Essential Features of Inquiry. You can use this map in your classroom when you introduce Immersion Units to your students. The science inquiry process is dynamic and does not necessarily follow a linear order. For example, a student may develop an explanation that leads to a new scientific question, or that student may revisit evidence in light of alternative explanations. On some occasions, multiple features of an explanation may overlap, or, depending on the type of lesson, some features may have more emphasis than others. These variations allow learners the freedom to inquire, experience, and understand scientific knowledge. The Five Essential Features of Inquiry describe how engaging in science inquiry unfolds in the classroom. Student Groups In this unit, students often work in groups. When working as a team in a group, the ideal is to have groups no larger than four students. Whatever the group size is, all students in the team need to have a job to do so they are individually accountable for focusing on the current science lesson. More information and suggestions for choosing groups is provided in specific lesson implementation guides. Think Aloud Strategy What Makes Things Float? uses the Think Aloud strategy throughout the unit. The Think Aloud is a teaching approach whereby the teacher makes important thinking and reasoning processes explicit for learners by describing aloud the thinking process involved in a certain activity. In this way, the teacher makes visible to students the otherwise invisible thought processes that are essential for scientific reasoning to occur. Example Think Aloud dialog suggestions are included in the lessons that recommend using this strategy. Think-Pair-Share Think-Pair-Share is a cooperative learning technique that allows students to think before they respond to a prompt, to test their response on their partner, and then to share their response (possibly revised) with a larger group. Specific instructions for implementing the Think-Pair-Share strategy are discussed in the Immersion Unit Toolbox. What Makes Things Float? uses this technique throughout the unit. REAPS REAPS is a method of formative assessment that combines the time-tested ideas of Blooms Taxonomy with new research on student assessment. The level of thinking increases from basic recall to complex analysis and predictions. On each Lesson Snapshot page is a series of REAPS prompts. This series of prompts is a simple tool that can be used throughout or at the end of each lesson. They 16 Buoyancy and Density: What Makes Things Float?

17 Unit Overview 17

18 can be used individually, in pairs or in groups to review what students know and are able to do. This provides an opportunity for the teacher to modify instruction as necessary based on student responses. Here are the types of prompts included in the REAPS. R Recall new knowledge: Determines whether the student has learned the basic knowledge that is related to and supports the key concept including lists, drawings, diagrams, and definitions. E Extend new knowledge: Determines whether the student can organize the basic knowledge related to the key concept such as compare, contrast, classify. A Analyze knowledge: Encourages the student to apply or interpret what they have learned including developing questions, designing investigations, interpreting data. P Predict something related to new knowledge: Engages the student in thinking about probable outcomes based on observations and to engage S them in a new topic that builds on prior knowledge. Self/Peer Assess: Encourages students to take responsibility for their own learning. Includes methods and/or activities for students to assess their own learning and/or that of their peers. The prompts increase in cognitive difficulty with Recall as the easiest and Predict as usually the most advanced. Students most likely demonstrate confidence and ability when responding to the first few prompts, while demonstrating continuous improvement in responding to the Apply and Predict prompts. Students are not expected to master all of the skills, but are encouraged to extend their thinking. Suggested responses are included in italics after the prompts. While the suggestions are good responses, other responses may be just as good or worth recognition if they include appropriate supporting evidence and reasoning. 18 Buoyancy and Density: What Makes Things Float?

19 S t e p 1 Overview Students initial curiosity about key concepts in density and buoyancy is stimulated by a series of Float Demos which contain odd pairs of floating and sinking objects. Students are encouraged to make and record observations and raise questions. In the second lesson, students will learn how to develop testable questions. They will be guided to focus their initial questions into scientifically testable ones that can be explored through this Unit. Step 1 Overview 19

20 20 Buoyancy and Density: What Makes Things Float?

21 Step 1 Lesson 1 Snapshot Key Concepts Scientists observe natural phenomena, pose questions, and wonder based on their observations. Evidence of Student Understanding The student will be able to: observe the floating puzzles and develop questions about what they see related to the question, What makes things float? Time Needed 50 minutes Materials For each student: science notebook 1 copy of Student Page 1.1A: Floating Puzzles For each group of 4 6 students 1 transparent container deep enough for pairs of objects to float in water Float Demo materials Demo 1: diet and regular soda cans (12 oz. cans) Demo 2: two capped/sealed plastic vials of different volumes but same mass and a balance to confirm the mass Demo 3: wood and copper cubes from density cube set For the class prominently displayed banner that reads: What makes things float? Floating Puzzles 1. Introduce to the whole class this Immersion Unit s overarching question, What makes things float? 2. Divide the class into groups of four to six students and distribute to each student a copy of Student Page 1.1A: Floating Puzzles. 3. Explain the procedure the class will follow for observing and recording questions about each of the Floating Puzzles. 4. Guide student groups to explore as a class the first of the three Float Demos. Have students record on Student Page 1.1A: Floating Puzzles or in their science notebooks the observations they make and questions that arise. Stop and discuss as a class the types of observations and questions students are making to help prompt students to think of additional ideas. 5. Repeat the procedure for making, recording, and discussing observations and questions for the other two Float Demos. 6. Have student groups review their questions and observations about the Float Demos. From the questions recorded, instruct each group to select three questions that they find most interesting, and write them on a transparency or post them in a designated location where they will remain throughout the unit (though they will be revised and rearranged). 7. Introduce the What Makes Things Float? Chart, and work as a class to complete a row based on Lesson 1 experiences. 8. Use the REAPS questions throughout the lesson where appropriate. (continued on following page) Step1 Lesson 1: Floating Puzzles 21

22 REAPS Questions R What pair of floating/sinking objects were you most curious about? Students responses to this question may help you gauge their prior knowledge about density and what makes things float. E What other floating or sinking objects have you observed in your everyday life? Students may recall floating a toy in the bathtub, being in a boat, a sponge floating in dishwater, or any other number of typical experiences. A Students will analyze their observations and questions in later lessons. P What do you think is important to notice to predict if something will float or not? Use this question to assess students preconceptions about factors that determine if an object will sink. Students may predict at this time, for example, that how heavy an object is determines if it will float. S What did you think about today that you had not thought about before? Prompt students to reflect on what they wondered as they made observations. 22 Buoyancy and Density: What Makes Things Float?

23 Teacher Background Information In this unit, students investigate and gather evidence to explain density as a property before using the term density. The unit opens with the overarching question that will underlie each lesson in the unit, What makes things float? Students are guided through a series of activities and lessons to first construct the evidence needed to explain the relationship between mass and volume as a property that makes it possible to predict what will float. Then, students continue to inquire and engage in readings and lessons to learn about buoyancy. The formulas for these properties are abstract and are intentionally omitted until later lessons, as students first engage in concrete experiences to identify the factors that influence whether an object will float or sink. Science Notebooks Density and Buoyancy is written with specific references for students to make entries in their science notebook. The use of science notebooks for each student is strongly encouraged for all science lessons, particularly those throughout this unit. Specific opportunities for using science notebooks in this unit are explicitly described where appropriate. A bound notebook works well for a science notebook because its pages cannot easily be torn out or replaced, handouts and other loose pieces of paper can easily be taped in, and it is inexpensive. Notebook entries can include written observations, labeled drawings, date, time, environmental conditions or weather, and even small samples pressed between the pages. The important thing to remember when drawing and/or writing for scientific purposes is to draw or write only about what can be directly observed. Think-Pair-Share Think-Pair-Share is a cooperative learning technique that is used frequently in this Immersion Unit. It allows students to think before they respond to a prompt, to test their response on their partner, and then to share their response (possibly revised) with a larger group. Specific instructions for implementing the Think-Pair-Share strategy are discussed in the Immersion Unit Toolbox. Step1 Lesson 1: Floating Puzzles 23

24 Advance Preparation Density Cubes Density cubes are used throughout this unit, although they are purposely not referred to as density cubes before Step 3 because students develop an understanding of density by engaging in a series of inquiries. In preparation for using these cubes, consider the following: Obtain enough sets of cubes to have at least two sets for every four students. If possible, use cube sets that include a wooden cube that sinks. Alternatively, it may be possible add a sinking wooden cube of the same size to your sets. While this is not necessary, it is a good way to help break the common misconception that all wood floats. Number the cubes with a fine-tip permanent marker, using the same number key for each set so that it is easy for the class to communicate about the cubes. Once the cubes become wet, the wooden cubes are particularly difficult to distinguish. Prepare a poster with the numbers and types of cubes they refer to so the students can refer to it throughout the unit. Consider waxing or varnishing the wooden cubes so that they do not absorb water and deteriorate. Any time the wooden cubes are used, have students remove them from the water and dry them off as soon as the trial is completed. Over time, the wooden cubes will change density by absorbing water and swell and split. If storing the cubes in their original container, remove or cover any reference to the word density. In this unit, students investigate and gather evidence to explain density as a property before using the term density. Refer to the cubes as blocks or cubes, not density cubes in class. (continued on following page) 24 Buoyancy and Density: What Makes Things Float?

25 Container for Floating Objects Throughout the unit, students will test a variety of cube combinations and some other objects to see if they float. For each group of 4 6 students, provide at least one transparent container of water that can be used for each of these investigations. You may consider several options for this equipment: 1000 ml beaker small aquarium clear 2-liter soda bottle with top cut off other recycled clear plastic containers or glassware that is large enough for students to reach a hand into and sink 4 5 cubes banded together Floating Puzzle Preparations Prepare in advance materials for the Float Demos to be observed by groups of 4 6 students. Students will observe and ask questions about each puzzle, working as a class on each puzzle before moving on to the next. Student Page 1.1A: Floating Puzzles provides a format for recording observations and questions; plan for having copies of this page for each student or you may wish to have them copy a similar format directly into their science notebooks. Demo 1: Two soda cans (one diet and one regular) in a deep transparent container filled with water. The 12 oz. cans work most consistently. The demo will look something like the following: Diet soda can floats Regular soda can sinks Test cans in advance because canning errors sometimes result in non-consistent behavior. When placing cans into the water, be careful to tip each can slightly to avoid capturing a bubble of air in the bottom, concave end of the can. Demo 2: Measure and fill two capped/sealed vials with table salt or sugar so that they have different volumes but the same mass. Use small plastic vials with caps. Select vials that are obviously of different size. If possible, use vials that are transparent so students see contents plus air pocket. A plastic coin tube and empty medicine bottle are used in the sample photo. Add a solid (like salt or sugar) such that the total mass (continued on following page) Step1 Lesson 1: Floating Puzzles 25

26 of vial, cap and contents are the same for both vials. Cap tightly and place these in a container of water. Provide a balance so that students can confirm that the mass is the same for both vials. Demo 3: A container of water with two density cubes. One cube is made of wood and the other of metal (brass or copper). If available in your density cube sets, use the wooden cube that sinks to cause students to wonder about any preconceptions they may have that all wood floats. What Makes Things Float? Chart Throughout this unit, students are prompted to make note as a class about what was observed and learned from a lesson. It is important to provide this continuity to keep track of the big explanation that students are developing over several weeks they are gathering evidence and building their understanding of the properties that determine whether an object will sink or float. This graphic organizer offers a concrete method for tracking that progress. It is recommended that you both keep a classroom copy of the chart and have students keep a copy in their science notebooks. Decide in advance the logistics for doing this. You may wish to make the classroom chart on an overhead transparency if it is challenging to post it on the wall. If you are able to post the chart, it will be easier to refer to it on a regular basis; however, you will need to manage a way to keep from displaying an earlier class chart to a later class. The What Makes Things Float? Chart has the following headings: What Makes Things Float? Chart What did we do in this lesson? What evidence did we collect? Big idea(s) I took away from the lesson How would you use that evidence to make a prediction? 26 Buoyancy and Density: What Makes Things Float?

27 Implementation Guide 1. Introduce to the whole class this Immersion Unit s overarching question, What makes things float? Explain that throughout this unit the students will be conducting investigations and lessons to help them explain what makes things float. Today, they will begin by observing some interesting pairs of floating and sinking objects. 2. Divide the class into groups of four to six students and distribute to each student a copy of Student Page 1.1A: Floating Puzzles. 3. Use the student page to explain the procedure the class will follow for observing and recording questions about each of the Floating Puzzles. Highlight the importance of making detailed observations and recording all the questions that arise. Instruct students to minimize water spillage and not to open any of the containers. 4. Travel around the room and guide student groups to explore the first of the three Float Demos. Have students record on Student Page 1.1A: Floating Puzzles or in their science notebooks the observations they make and questions that arise. Stop and discuss as a class the types of observations and questions students are making to help prompt students to think of additional ideas. 5. Repeat the procedure for making, recording, and discussing observations and questions for the other two Float Demos. Encourage students to make What did we do in this lesson? What Makes Things Float? Chart What evidence did we collect? comparisons among the Float Demos and revisit a demo if needed. 6. Have student groups review their questions and observations about the Float Demos. From the questions recorded, instruct each group to select three questions that they find most interesting. Make the questions visible to all students by either recording them on a wall chart or overhead transparency displayed for the class. As questions are posted, sort them for duplicates and roughly group them by similarities. These questions will be addressed in the next lesson and throughout the unit. Include all questions and statements at this point without correcting misconceptions or probing for answers. These are initial questions; expect many to be elementary or to reveal misconceptions. 7. Introduce the What Makes Things Float? Chart. Explain that this chart, along with their question wall, will be the focal points for the unit. The class will keep track of their work and learning about how to explain what makes things float. This chart will be dynamic so, students can change and add to it as their knowledge grows and changes. Work as a class to complete a row based on Lesson 1 experiences. This is an example of how the chart may look after this lesson: 8. Use the REAPS questions throughout the lesson where appropriate. Big idea(s) I took away from the lesson How would you use that evidence to make a prediction? Looked at Float Demos Observations Some things are hard to predict if they will float or not. Not sure Step1 Lesson 1: Floating Puzzles 27

28 28 Buoyancy and Density: What Makes Things Float?

29 Directions Student Page 1.1A: Floating Puzzles Observations: Make observations on the puzzle on your table. Watch what is happening and write everything you see. Details are very important! You may also talk to your team members about what you see. Questions: After completing your observations, write down as many questions as you can about the puzzle you just observed. Base your questions on your observations. Puzzle #1: Cubes Observations: Questions: Puzzle #2: Vials Observations: Questions: Puzzle #3: Soft drink cans Observations: Questions: Student Page 1.1A: Floating Puzzles 29

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31 Step 1 Lesson 2 Snapshot Key Concept Scientists observe natural phenomena and develop testable questions based on their observations Evidence of Student Understanding The student will be able to: identify questions that are testable in the classroom from a list of testable and non-testable examples. convert initial wonderings about the floating puzzles into testable questions. Time Needed 50 minutes Materials For each student: 1 copy of Student Page 1.2A: Questions for Investigations For the class list of questions generated during Lesson 1.1 (either on transparency or posted on the wall) Crafting Testable Questions 1. Point to the What Makes Things Float? question that is guiding this unit, and reflect back on both the student questions from Lesson 1.1 and the What Makes Things Float? Chart. Explain that in this lesson the class will think more about questions they are wondering (stimulated by the floating demos), to consider the following: Are the questions related to the overarching question, What makes things float? Are their questions testable? 2. Distribute Student Page 1.2A: Questions for Investigations, and use a Think-Pair-Share strategy for students to complete and review the exercise. 3. Apply the same strategies as used on Student Page 1.2A: Questions for Investigations, to have students refine their questions and statements from Lesson 1.1 to be testable questions. Give students the opportunity to contribute additional questions as they arise, too. 4. Use the REAPS questions throughout the lesson where appropriate. REAPS Questions R Name one question that we discussed that is not readily testable in our classroom? Explain why it is not testable. Look for students to be able to explain that a testable question in this context needs to suggest an investigation that can be conducted using the equipment available in the classroom. E Why is a question sometimes not testable? What does that mean? Some questions are not testable because they do not lend themselves to experimentation. Being testable means that an answer to the question can be found based on measurable observations. A How are testable questions related to variables? Testable questions can be investigated, which means that the question asks about variables that can be controlled and/or manipulated, measured and/or observed. P Which of the questions developed by your class do you think will be the most challenging to answer? Why do you think so? S How did working on questions during this lesson change the way that you think about what makes things float? Step1 Lesson 2: Crafting Testable Questions 31

32 32 Buoyancy and Density: What Makes Things Float?

33 Teacher Background Information Several common misconceptions about density and buoyancy may surface during the discussions in this unit. For example, one might think that things float because they are made of wood and things sink because they are made of metal. However, many people know that wooden boats can sink and that boats made of metal (tankers, military boats) can float. If this kind of discussion appears during the class discussion about their questions, make note of the misconception to be certain it is addressed by the end of Lesson 2.3, and resist providing an answer at this time. During this and the previous lesson, students are engaging in thinking about what makes things float and beginning to explore and observe demonstrations that the class can have in common to discuss. In the next two lessons, students will gather evidence to use in developing an explanation for density in Lesson 2.3. This is an intentional design for students to start with concrete examples of objects floating, explore variables that they likely think affect if an object floats, and then look for patterns in their evidence to explain the abstract concept of density. Step1 Lesson 2: Crafting Testable Questions 33