Chemistry, Quarter 4, Unit 4.1. Behaviors of Gases. Overview

Transcription

1 Chemistry, Quarter 4, Unit 4.1 Behaviors of Gases Overview Number of instructional days: 8 (1 day = 50 minutes) Content to be learned Determine the degree of change in the pressure of a given volume of gas when the temperature changes incrementally. Determine how volume, pressure, temperature, and amount of gas affect each other (PV=nRT) Essential questions What is the degree of change in the pressure of a given volume of gas when the temperature changes incrementally? Science processes to be integrated Collect, use, analyze, and interpret data including graphs. Use evidence from an investigation to draw conclusions. Use a simulation and models. Perform calculations. Ask questions and formulate hypotheses. Make appropriate use of tools and techniques. How are the volume, pressure, and temperature of a gas interrelated? 45

2 Chemistry, Quarter 4, Unit 4.1 Behaviors of Gases (8 days) Written Curriculum Grade-Span Expectations PS1 - All living and nonliving things are composed of matter having characteristic properties that distinguish one substance from another (independent of size or amount of substance). PS1 (9-11) INQ 1 Use physical and chemical properties as determined through an investigation to identify a substance. PS1 (Ext) 1 Students demonstrate an understanding of characteristic properties of matter by 1b determining the degree of change in pressure of a given volume of gas when the temperature changes incrementally (doubles, triples, etc.). PS1 (Ext) 1 Students demonstrate an understanding of characteristic properties of matter by 1bb quantitatively determining how volume, pressure, temperature and amount of gas affect each other (PV=nRT) in a system. Clarifying the Standards Prior Learning In grades K 4, students demonstrated an understanding of states of matter by describing properties of solids, liquids, and gases. They have been exposed to temperature as a physical property. In grades 5 8, students demonstrated an understanding of states of matter by explaining the effect of increased and decreased heat energy on the motion and arrangement of molecules. Students have created diagrams or models to represent the states of matter at a molecular level. Students have observed physical processes of evaporation and condensation or freezing and melting and described these changes in terms of molecular motion and conservation of mass. In previous units and grades, students explained the states of a substance in terms of the particulate nature of matter and the forces of interaction between particles. Additionally, students have studied phase changes in matter (Unit 1.1) in conjunction with the particulate theory of matter and kinetic molecular theory. Current Learning Students have spent a considerable amount of time in previous units and grades investigating how the forces of interaction between particles affect the state of a substance. Instruction for these concepts should be at the reinforcement level. Students have not been exposed to the quantitative effects that changing pressure has on the temperature of a gas. Additionally, they have not looked at how changing many variables such as volume, pressure, temperature, and the amount of a gas affect each other in a system. 46

3 Chemistry, Quarter 4, Unit 4.1 Behaviors of Gases (8 days) In this unit, students determine the degree of change in pressure of a given volume of gas when the temperature changes incrementally (doubles, triples, etc.). Students quantitatively determine how volume, pressure, temperature, and amount of gas in a system affect each other (PV = nrt). Therefore, instruction for these concepts will be at the developmental level. The processes that students need in order to master the content in this unit of study are collecting, using, analyzing, and interpreting data, including graphs. Students collect, use, and analyze data from an investigation in order to determine the degree of change in the pressure of a given volume of gas when the temperature changes incrementally. When writing their conclusions, students will use data as evidence for all conclusions. They will graph the effect of pressure on the temperature of a gas. They will determine quantitatively how volume, pressure, temperature, and the amount of gas in a system affect each other (PV = nrt) by interpreting data and performing calculations. Examples of hands-on experiences include Boyle s Law; use of temperature and pressure probes; and online simulations that demonstrate the relationship between pressure, temperature, and volume. Whenever students perform investigations, they will be required to ask testable questions, and make hypotheses supported by data from one or more sources. During this unit, it is important that students develop skill in dimensional analysis for conversions of pressure, temperature, and volume. Additionally, students must have some background knowledge on moles in order to use the PV = nrt equation quantitatively. It will be important that this concept is introduced to students prior to beginning this instruction. They need to review the concepts of absolute temperature and the Kelvin scale. As an extension, students may be introduced to stoichiometric conversions (if they are required to calculate moles from grams of a gas or vice versa). Future Learning During units on respiration and photosynthesis, students will use their knowledge of gas laws on organisms. Additional Findings When algebraic equations and graphs of equations are used in studying science, the point should be made frequently that formulas and graphs are intended to describe phenomena, but may not necessarily well. "Why doesn't it fit exactly?" is a question to which increasing sophisticated answers should be given. Answers about errors of observation should come first, then answers about choosing the wrong formula to fit idealized data; later, answers should include uncontrolled influences and inappropriate ranges of application; finally, should come the answer, the world just doesn't seem to act as simply as the mathematics (Benchmarks for Science Literacy, p. 216). Pupils may not regard gas as having weight or mass. It has been suggested that this is because the children's most common related experience is that gases tend to rise or float. This view supported by studies, which show that children ages 9 13 tend to predict that gases have the property of negative weight, and hence the more gas that is added to a container, the lighter the container becomes. Until they construct the idea that gases have mass, pupils are unlikely to conserve mass when describing chemical changes that involve gases as either reactants or products. (Making Sense of Secondary Science, p. 80) The idea that there is no difference between heat and temperature is a type of thinking found in pupils aged (Making Sense of Secondary, p. 139) 47

4 Chemistry, Quarter 4, Unit 4.1 Behaviors of Gases (8 days) Studies have shown that 11- to 13-year-old pupils think that only wind, not still air, has pressure. Pupils tend to associate pressure in gases with moving air, assuming pressure acting in the direction of motion. Atmospheric pressure pushing was mentioned, but few pupils explained it in terms of balancing pressures. (Making Sense, p. 152). Over a period of years, therefore, students should have experiences leading to the realization that symbolic equations can be used interchangeably with graphs, tables, and words to summarize data and to model real-world relationships (as in physics, finance, engineering, etc.) Care must be taken, however not to go over the heads of the students. Variables should be selected for study that are interesting and observable (or measurable), and the focus should be on the simple relationships between one variable and another outlined in Science for All Americans. (Benchmarks for Science Literacy, p. 215) Science uses algebra in modeling how changes in one quantity affect changes in other quantities. Much of physics, chemistry, and engineering and, increasingly, biology depend on algebraic representations. In Project 2061, we don't expect students to remember formulas for acceleration or parallel circuits or mass action; nor do we expect them to be able to perform algebraic manipulations or solve simultaneous equations. We do expect them to acquire an understanding of proportionality, the ability to read an algebraic formula, and to develop the ability to relate the shape of a graph to its implications for how some aspect of the world behaves (Benchmarks for Science Literacy, p. 216). 48

5 Chemistry, Quarter 4, Unit 4.2 Nuclear Chemistry Overview Number of instructional days: 12 (1 day = 50 minutes) Content to be learned Explain and/or model how the nuclear makeup of atoms governs alpha and beta emissions. Explain how changes in the nucleus of an atom results in the formation of new elements. Explain the concept of half-life. Use the half-life principle to predict the approximate age of a material. Differentiate between fission and fusion in nuclear reactions. Explain how fission and fusion are related to element changes and energy formation. Essential questions How does the makeup of atoms determine if an atom will emit an alpha particle or beta particle? What happens to the nucleus of an atom when it undergoes a nuclear change to become a new element? Science processes to be integrated Collect, use, analyze, and interpret data including graphs. Use evidence from an investigation to draw conclusions. Use a simulation and models. Perform calculations. Ask questions and formulate hypotheses. Make appropriate use of tools and techniques. How can half-life be used to predict the approximate age of material? What are the major differences in the processes involved in and products produced by fission and fusion? How are fission and fusion related to element changes and energy formation? 49

6 Chemistry, Quarter 4, Unit 4.2 Nuclear Chemistry (12 days) Written Curriculum Grade-Span Expectations PS 2 - Energy is necessary for change to occur in matter. Energy can be stored, transferred, and transformed, but cannot be destroyed. PS2 (9-11) INQ+SAE -6 Using information provided about chemical changes, draw conclusions about and explain the energy flow in a given chemical reaction (e.g., exothermic reactions, endothermic reactions). PS2 (9-11) 6 Students demonstrate an understanding of physical, chemical, and nuclear changes by 6c explaining and/or modeling how the nuclear make-up of atoms governs alpha and beta emissions creating changes in the nucleus of an atom results in the formation of new elements. 6d explaining the concept of half-life and using the half-life principal to predict the approximate age of a material. 6e differentiating between fission and fusion in nuclear reactions and their relation to element changes and energy formation. Clarifying the Standards Prior Learning In grades 5 8, students used fossil evidence to understand the history of life on earth. They have been introduced to the concept of aging materials. In grades 7 8, students used models or diagrams to show the difference between atoms and molecules. They explained that, when substances undergo physical changes, the appearance may change, but the chemical makeup and chemical properties do not, and that, when substances undergo chemical changes to form new substances, the properties of the new combinations may be very different from those of the old. In grade 9, students related how geologic time is determined using various dating methods, for example, radioactive decay and half-life. Additionally, in previous units, students learned about the structure of the atom, isotopes, and average atomic mass. They also used the periodic table and learned how subatomic particles combine to make different elements. Current Learning This is the first time that students have been asked to explain and/or model how the nuclear makeup of atoms governs alpha and beta emissions. Students have not been asked to explain how changes in the nucleus of an atom result in the formation of new elements. Students have never been exposed to the concept of half-life and have never used the half-life principle to predict the approximate age of a material. In addition, students differentiate between fission and fusion in nuclear reactions, concepts that have not been introduced prior to this unit. All of this content should be taught at a developmental level. 50

7 Chemistry, Quarter 4, Unit 4.2 Nuclear Chemistry (12 days) Students explain and model how the nuclear makeup of atoms governs alpha and beta emissions. They will explain how changes in the nucleus of an atom results in the formation of new elements. The students will explain the concept of half-life and use the half-life principle to predict the approximate age of a material. In this unit of study, students differentiate between fission and fusion in nuclear reactions. They explain how element changes and energy formation are related. Students collect, use, analyze, and interpret data, including graphs. They use evidence from an investigation to draw conclusions. They use a simulation to illustrate a model and perform calculations, question, and hypothesize. The students use tools and techniques appropriately. When students have been exposed to alpha and beta emissions, they can then relate this to element change and energy formation. Future Learning This will be the last exposure to this content, so it is very important that it be taught to the level of application, at least. Additional Findings The idea of half-life requires that students understand ratios and the multiplication of fractions, and be somewhat comfortable with probability. Games with manipulatives or computer simulations should help them understand how a constant proportional rate of decay is consistent with declining measures that only gradually approach zero. The mathematics of inferring backwards from measurements to age is not appropriate for most students. They need only know that such calculations are possible. (Benchmarks for Science Literacy, p. 79) Having learned earlier that all the atoms of an element are identical and are different from those of all other elements, students now come up against the idea that, on the contrary, atoms of the same element can differ in important ways. This revelation is an opportunity as well as a complication scientific knowledge grows by modifications, sometimes radical, of previous theories (Benchmarks, p. 79). By the end of 12th grade, students should know that the nucleus of radioactive isotopes is unstable and spontaneously decays, emitting particles and/or wavelike radiation. It cannot be predicted exactly when, if ever, an unstable nucleus will decay, but a large group of identical nuclei decay at a predictable rate. This predictability of decay rate allows radioactivity to be used for estimating the age of materials that contain radioactive substances. (Benchmarks, p. 80) 51

8 Chemistry, Quarter 4, Unit 4.2 Nuclear Chemistry (12 days) 52

9 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry Overview Number of instructional days: 12 (1 day = 50 minutes) Content to be learned Explain the relationships between or among the energy produced from nuclear reactions, the origin of elements, and the lifecycle of stars. Apply the properties of waves and particles to explain the composition of stars and other bodies in the universe. Identify and describe the characteristics common to most stars in the universe. Explain how fusion is related to the process of star formation. Describe the ongoing nuclear processes involved in star formation. Explain how heat from radioactive decay affects the rock cycle. Relate how geologic time is determined using radioactive decay. Describe various dating methods to determine the age of different rock structures. Explain how the chemical processes of the earth alter the crust. Use evidence to investigate or explain conservation of matter during the rock cycle. Calculate the age of rocks from various regions using radioactive half-life, given its constituent elements, isotopes, and rate of decay; use these values to provide evidence for geologic relationships between/among the regions. Science processes to be integrated Use, analyze, and interpret data including graphs. Use evidence to draw conclusions. Use a simulation to illustrate a concept. Perform calculations. Question and hypothesize. Make appropriate use of tools and techniques. Examine patterns of change. Use models and scales. 53

10 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry (12 days) Essential questions How is nuclear fusion related to the process of star formation and the life cycle of stars? How do chemical processes like weathering, or element cycling affect the earth s crust? How does the wavelength of light emitted by a star reveal its composition and age? How does heat from radioactive decay affect the rock cycle and enable us to determine a rocks location and age? What are properties and characteristics of stars? How is matter conserved throughout the rock cycle? Written Curriculum Grade-Span Expectations ESS1 - The earth and earth materials as we know them today have developed over long periods of time, through continual change processes. ESS1 (9-11) SAE+ POC 3 Explain how internal and external sources of heat (energy) fuel geologic processes (e.g., rock cycle, plate tectonics, sea floor spreading). ESS1 (9-11) 3 Students demonstrate an understanding of processes and change over time within earth systems by 3a explaining how heat (produced by friction, radioactive decay and pressure) affects the Rock Cycle. 3c investigating and using evidence to explain that conservation in the amount of earth materials occurs during the Rock Cycle. 3d explaining how the physical and chemical processes of the Earth alter the crust (e.g. seafloor spreading, hydrologic cycle, weathering, element cycling). ESS1 (9-11) INQ+POC+ MAS 4 Relate how geologic time is determined using various dating methods (e.g. radioactive decay, rock sequences, fossil records). ESS1 (9-11) 4 Students demonstrate an understanding of processes and change over time by 4a describing various dating methods to determine the age of different rock structures. 54

11 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry (12 days) ESS3 - The origin and evolution of galaxies and the universe demonstrate fundamental principles of physical science across vast distances and time ESS3 (9-11) SAE -7 Based on the nature of electromagnetic waves, explain the movement and location of objects in the universe or their composition (e.g., red shift, blue shift, line spectra) ESS3 (9-11) 7 Students demonstrate an understanding of processes and change over time within the system of the universe (Scale, Distances, Star Formation, Theories, Instrumentation) by... 7a applying the properties of waves/particles to explain the movement, location, and composition of the stars and other bodies in the universe. ESS3 (9-11) POC+SAE 8 Explain the relationships between or among the energy produced from nuclear reactions, the origin of elements, and the life cycle of stars. ESS3 (9-11) 8 Students demonstrate an understanding of the life cycle of stars by 8a relating the process of star formation to the size of the star and including the interaction of the force of gravity, fusion, and energy release in the development of the star identifying and describing the characteristics common to most stars in the universe. 8b Describing the ongoing processes involved in star formation, their life cycles and their destruction. Clarifying the Standards Prior Learning In grades K 2, students demonstrated an understanding of earth materials by comparing and sorting objects according to similar or different physical properties. Students observed and recorded data about physical properties including size, shape, color, texture, smell, and weight. Students used attributes of properties to state why objects are grouped together (such as things that roll or things that are rough). Students described, compared, and sorted rocks and soils by similar or different physical properties such as size, shape, color, texture, smell, and weight. In grades 3 4, students furthered their understanding of characteristic properties to include temperature and flexibility by citing evidence to support conclusions about grouping. Students demonstrated an understanding of physical change by observing and describing physical changes such as freezing, thawing, or tearing paper. Students described, compared, and sorted rocks, soils, and minerals by similar or different physical properties such as size, shape, color, texture, smell, weight, temperature, hardness, or composition. Students also cited evidence to support why rocks, soils, or minerals are or are not classified together. They have limited experience with topics relating to stars (e.g., constellations, many billions of stars in galaxies). 55

12 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry (12 days) In grades 5 8, students demonstrated an understanding of processes and change over time by representing the processes of the rock cycle in words, diagrams, or models. They also cited evidence and developed a logical argument to explain the formation of a rock, given its characteristics and locations, for example classifying rock types using identification resources. Students demonstrated an understanding of the conservation of matter by citing evidence to conclude that the amount of matter before and after undergoing a physical or chemical change in a closed system remains the same. To determine how the earth has changed and will continue to change over time, students evaluated slow processes such as weathering any of the chemical or mechanical processes by which rocks exposed to weather undergo chemical decomposition and physical disintegration. Students also cited evidence and developed a logical argument for plate movement using fossil evidence, layers of sedimentary rock, location of mineral deposits, and shape of the continents. Students have identified that the sun is a medium-sized star. In unit 1 of this course, students learned to classify matter using physical and chemical properties. Atomic structure in unit 2 also described the structure of the atom and its relationship to those physical and chemical properties of the elements. Students also studied balancing equations and the law of conservation of matter. In unit 4.2, students explained and modeled how the nuclear makeup of atoms governs alpha and beta emissions. They explained how changes in the nucleus of an atom results in the formation of new elements. The students explained the concept of half-life and used the half-life principle to predict the approximate age of a material. Current Learning Students have been studying the characteristics of rocks since early elementary school. The slow processes, like weathering, have been taught in middle school. In this unit of study, instruction around how chemical processes change the earth s crust should be at the reinforcement to drill-and-practice level. This unit of study will utilize rocks, minerals, and other earth phenomena to provide students with authentic, real-world examples of the use of this information. In this unit of study, students make connections between chemical processes and the formation and classification of rocks. Students also apply an understanding of chemical and physical processes to explain processes that drive seafloor spreading and element cycling. To this point in their education, students have focused on the physical processes that drive these phenomena. Students will now use this knowledge to help explain how the earth s crust is constantly being altered through chemical processes over time. Students learn that rocks can be identified by their chemical and physical properties. Students have identified rocks based on their physical characteristics and where they were formed. At this level, students examine the chemical as well as the physical properties of rocks. Since rocks are made up of one or more minerals, it is the identification of mineral properties that allows students to examine their chemical and physical properties to identify an unknown. While there is a standard list of physical properties used to identify minerals, the best physical property is one that gives a unique and consistent result. This is an idealized concept. Students need to use a range of tests of several known physical properties in order to collect enough positive test results to identify an unknown mineral. Both structure and composition affect certain physical properties of minerals. It is through the proper use of these properties that minerals are reliably identified. 56

13 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry (12 days) Students in middle school have already studied the basics of the rock cycle. In this unit of study, students focus on how heat and pressure affects the rock cycle. Students learn that igneous rocks are a direct result of the heating, melting, and recrystallization of rock material. Since rocks are made up of minerals with definite chemical compositions, the way that rocks change as a result of this heating and cooling can be predicted in the say way that it could if it were a chemical reaction that takes place in a classroom. Students are not required to know the composition of minerals; instead, they will be required to know that heat and pressure causes these chemical substances to behave in predictable ways. The same is true for metamorphic rocks that are formed from preexisting rocks exposed to extreme amounts of heat and pressure. This processes changes the character of the initial rocks and minerals in distinctive ways. Students also need to investigate and use evidence to explain that conservation in the amount of earth materials occurs during the rock cycle. They learn that rocks are formed from pre-existing rock material. Under the effects of evaporation, precipitation, heat, and pressure, these preexisting rocks form new rock. For example, metamorphic rock has the same chemical composition as the original rock it was formed from (in terms of % elements). This is because no minerals are added or lost in the recrystallization process. For example, the Ca:C:O ratio is the same in the sedimentary limestone rock as it is in the resulting metamorphic rock marble, because chemically they are both mainly calcium carbonate CaCO 3. Students have already learned that convection is responsible for the plate movements that causes seafloor spreading, but they now need to learn that these convection currents found in the asthenosphere (upper region of the mantle) are partly the result of the radioactive decay of elements that make up the mantle. Students need to explain how other physical and chemical processes cause the alteration of earth s crust. They examine the processes that occur during the rock cycle to explain how these processes cause chemical changes in the crust of the earth. Students apply their knowledge in order to explain how the earth s crust is constantly being altered through chemical processes over time. The study of the rock cycle takes a different focus at this time. Students now examine how chemistry can be used to explain why rocks change. Instruction for this unit should be presented at the reinforcement level. Much of this unit s content was first presented earlier in this course. The relationship between or among the energy produced from nuclear reactions is now applied to the origin of elements and the lifecycle of stars. Knowledge of fusion, temperature, and pressure will enable students to better understand the process of star formation. The students have experience with half-life and are now able to apply radioactive decay to the rock cycle and rock structures, as well as the ways geologic time and rock location are determined. Activities to support this may include a weathering brochure, Riding the Rock Cycle (children s book), chemical weathering lab, spectroscopy of light, and line emission spectra. They will explain the relationships between or among the energy produced from nuclear reactions, the origin of elements, and the lifecycle of stars, as well as how energy and matter are conserved. Students explain how fusion is related to the process of star formation. They describe the ongoing nuclear processes involved in star formation. Students explain how radioactive decay affects the rock cycle and relate how geologic time is determined using radioactive decay. They describe various dating methods to determine the age of different rock structures and calculate the age of rocks from various regions using radioactive half-life, given its constituent elements, isotopes, and rate of decay. They use these values to provide evidence for geologic relationships between/among the regions. The processes students need in order to master the content in this unit of study include using, analyzing, and interpreting data including graphs. They use evidence to draw conclusions; they use a simulation to 57

14 Chemistry, Quarter 4, Unit 4.3 Rock Star Chemistry (12 days) illustrate concepts; they perform calculations; they question and hypothesize; and they use scientific tools and techniques appropriately. The students use, analyze, and interpret data, including graphs related to the rock cycle, geologic time, rock location, and star formation. They use evidence to draw conclusions about the age of rocks and where they are located. They use simulations whenever possible to illustrate this unit's content. They perform half-life calculations to determine the age of rocks and geologic relationships. They question and hypothesize given data. The relationship between or among the energy produced from nuclear reactions is now applied to the origin of elements and the lifecycle of stars. Knowledge of fusion enables students to understand the process of star formation. The students have had experience with half-life and now apply radioactive decay to the rock cycle and rock structures, as well as how geologic time and rock location are determined. In this unit, students explain how heat and pressure affect the rock cycle. Future Learning If students take biology after chemistry, they will use the concept of half-life in biology in evolution as well as the evidence supporting earth s projected age and the history of life on our planet. As an extension, they may use this concept to incorporate the relative ages of rocks with the absolute ages of rocks together to determine the ages of fossils. In physics, nuclear topics will be explored. Additional Findings The idea of half-life requires that students understand ratios and the multiplication of fractions and be somewhat comfortable with probability. The mathematics of inferring backwards from measurements to age is not appropriate for most students. They need only that such calculations are possible. Having learned earlier that all the atoms of an element are identical and are different from those of all other elements, students now come up against the idea that, on the contrary, atoms of the same element can differ in important ways. This revelation is an opportunity as well as a complication scientific knowledge grows by modifications, sometimes radical, of previous theories (Benchmarks for Science Literacy, p. 79). Elements, such as carbon, oxygen, nitrogen, and sulfur, cycle slowly through the land, oceans, and atmosphere, changing their locations and chemical combinations. (Science for All Americans, p. 45). Stars condensed by gravity out of clouds of molecules of the lightest elements until nuclear fusion of the light elements into heavier ones began to occur. (Benchmarks, p. 65) 58