Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Toward High School Biology: Helping Middle School Students Make Sense of Chemical Reactions Jo Ellen Roseman Director Project 2061 Principal Investigator Biennial Conference on Chemical Education Penn State University July 29, 2012 Flow of the Paper Set l Defining the targeted knowledge l Curriculum development l Professional development and teacher materials l Student measures and findings l Teacher measures and findings 2 Coherence is the Goal “Black and White and Ten Red” Alexander Calder, 1957 “The only possible way in which individual knowledge can keep proportional pace with the surge of available knowledge is through a grasp of the relatedness of knowledge.’’ Jerome Bruner, 1960 Sample Item from Project 2061’s Assessment A table is made from wood that is cut from a tree. Where did most of the material that makes up the table originally come from? A. From sunlight B. From oxygen in the air C. From minerals in the soil D. From carbon dioxide in the air % Students Selecting Answer Choice C or D Where did most of the material that makes up a wooden table originally come from? 100% Minerals in the soil 90% 80% 70% 60% 50% 40% CO2 in the air 30% 20% 10% 0% 7 8 9 10 11 Grade 12 Entering Juniors Grad. College Students Across items assessing ideas about matter and energy, students commonly: l are confused about what is conserved in chemical reactions (atoms, molecules, energy), l do not associate growth with an increase in mass (and hence have no need to account for it), l think that the mass of gases is inconsequential (and hence doesn’t contribute significantly to growth), and l do not associate the growth and functioning of organisms with chemical reactions. 8 The Intervention: A New Curriculum Unit l 5-6 week replacement unit for 8th grade students l Focuses on a coherent set of ideas about chemical reactions and conservation in non-living and living systems that are central to science standards (Including A Framework for K-12 Science Education) l Engages students in interesting and appropriate phenomena that provide evidence for the ideas and for their explanatory power l Uses a variety of modeling tasks to guide students in interpreting the phenomena in light of the rearrangement and conservation of atoms during chemical reactions Measures of Quality, Feasibility, & Promise l Curriculum quality: satisfying criteria (coherent content + instructional support), conveying science content and design rationale to teachers l Feasibility of use: ability of a range of teachers to use it as designed 9 l Promise: improved student understanding of the set of ideas The development of both the curriculum and the assessment starts with the identification and clarification of learning goals. l Identify the learning goals to serve as the focus of development of both the curriculum unit and assessment items. l Clarify the expectations of the learning goals, including their boundaries. l Identify common misconceptions that might interfere with student learning. (These will be used as distractors in multiple choice items and explicitly addressed in the curriculum). 10 Chemistry Learning Goals l Many substances react chemically with other substances to form new substances with different characteristic properties. When substances react, the atoms that make up the molecules of the reactants rearrange to form the molecules of the products. The products have different properties because they are made up of different molecules. l Mass is conserved during chemical reactions because the total number of each kind of atom making up the molecules of the reactants is the same as the total number of each kind of atom making up the molecules of the products. (If the measured mass changes it is because atoms have entered or left the system). l Carbon-containing monomers can react to form carbon-containing polymers (and water molecules) that form visible structures. As in all chemical reactions, atoms are rearranged, not created or destroyed. 11 Excerpt from a Clarification …When substances react to form new substances, the atoms that make up the molecules of the reactants rearrange to form the molecules of the products... Students are expected to know that: l During a chemical reaction, the atoms that make up the molecules of the reactants rearrange to form the molecules of the products. l It does not matter how many atoms are rearranged, as long as some atoms of the product molecules are linked to atoms they were not linked to in the reactant molecules. l The products of a chemical reaction are made of the same types of atoms as the reactants, i.e., the atoms themselves do not change during the reaction. 12 Excerpt from a Clarification Boundaries: l Students are not expected to know the term “bond” or how chemical bonds are formed or broken during chemical reactions. l Students are not expected to know the parts of atoms or that electrons are involved in bonding. 13 Commonly Held Student Ideas l Atoms can be created during a chemical reaction. (AAAS Project 2061, n.d.) l Atoms can be destroyed during a chemical reaction. (AAAS Project 2061, n.d.) l The atoms of the reactants of a chemical reaction are transformed into other atoms (Andersson, 1986). 14 Biochemistry Learning Goals l Animals use polymers from food to make a variety of other polymers that make up their body structures. l Plants use glucose monomers they make to make a variety of polymers that become part of their body structures. l During the chemical reactions animals and plants use to build body structures, atoms are rearranged, not created or destroyed. The increase in the number of atoms making up the bodies of animals and plants results from a decrease in the number of atoms in their surroundings. 15 Excerpt from a Clarification Animals use polymers from food to make a variety of other polymers that make up their body structures. Students are expected to know that: l Except for bone, animal body structures (e.g., muscles, tendons, skin, scar tissue) are made mostly of proteins. l Proteins are polymers made of amino acid monomers linked together. The amino acid monomers are composed primarily of carbon, hydrogen, oxygen, and nitrogen atoms. l Animals need about 20 different kinds of amino acids to build all the proteins needed to make their body structures. l Animals break down polymers from food to obtain the monomers they need to build polymers that make up their body structures. 16 l The processes by which molecules from food become part of an animal’s body structures involve chemical reactions. Excerpt from a Clarification Boundaries: l Students are not expected to know that humans can make some, but not all, of the 20 amino acids and, therefore, must obtain these “essential” amino acids from food. l Students are not expected to know the chemical or structural formulas of particular proteins. (However, students should be able to compare products to determine if any atoms structural formulas of reactants and are rearranged.) 17 Commonly Held Student Ideas l Matter is created or destroyed, rather than transformed, in biological processes. (Smith & Anderson, 1986) l None of the atoms from food becomes part of the body structures of animals. All of the food an animal eats goes through the digestive system and ends up as waste. (AAAS Project 2061, n.d.) l Most of a plant's mass comes from minerals that the plant takes in from the soil (Vaz et al, 1997). 18 Once the learning goals have been clarified, the assessment development and curriculum development proceed in parallel: l Assessment items are developed, using commonly held student ideas as distractors, and are pilot tested and revised before being used in pretests and post-tests of student learning. l A coherent content storyline is developed for the curriculum unit, organizing key ideas from the learning goals into a logical sequence that takes account of commonly held student ideas. 19 ITEM: The diagram below shows models of the molecules that make up two different substances. In the diagram, atoms are represented by circles, and the molecules are represented by two or more circles connected to each other. The different colored circles represent different types of atoms. Which of the following could represent one of the molecules that result from the chemical reaction between these two substances? Why? A. 20 Because nothing happens to the structure of the molecules during a chemical reaction. B. Because some of the atoms are now connected to different atoms than they were in the starting molecules. C. Because the molecules that result from a chemical reaction have to include every type of atom from the starting molecules. D. Because new types of atoms are formed during chemical reactions. SB04-2 ITEM: A rabbit eats some grass. What happens to the grass once it is inside the rabbit’s body? Rabbit eating grass. Photo (CC) by Larry D. Moore. A. All of the grass is digested down to individual atoms that are destroyed, and disappears. B. All of the grass goes through the digestive system and ends up as waste. C. Some of the grass goes through chemical reactions and becomes part of the rabbit’s body. D. Some of the grass gets added to the rabbit’s body without going through any chemical reactions. SB18-1 Content Story Line for the Curriculum Unit A Content Story Line is a logical sequence of ideas that, when linked to evidence, contributes to student understanding of the learning goals. To remind us of the importance of providing evidence for each idea and helping students link the evidence to the idea, we organize unit development in a table that lists the idea (claim), evidence, and reasoning for each lesson. Evidence consists of observable phenomena and/or data. Reasoning consists of the logical step-by-step argument needed to link the evidence to the claim, often involving models. 22 Content Story Line for the Curriculum Unit A Content Story Line is a logical sequence of ideas that, when supported by evidence, contributes to student understanding of the learning goals. To remind us of the importance of providing evidence for each science idea and helping students link the evidence to the idea, we organize unit development in a table that lists the idea (claim), evidence, and reasoning for each lesson. Evidence consists of observable phenomena and/or data. Reasoning consists of the logical sequence of steps of the argument linking the evidence to the claim, often involving models. 23 Excerpt from the Chemistry Content Story Line Sequence of Ideas for Chapter 1 When substances interact, they can form substances with different properties from the starting substances. If two substances have different properties then they are different substances. Different substances have different properties because they are made up of different molecules. Although new substances form, they are made up of the same kinds of atoms as the starting substances. During chemical reactions, the atoms of the molecules of the reactants break apart from each other and rearrange to form the molecules of the products. No atoms are created or destroyed, so the number of each kind of atom in both reactants and products is the same. Polymers are made during chemical reactions that link monomers together. The monomers and polymers have different properties and, hence, are different substances. Polymers can link together to form visible structures. As in all chemical reactions, atoms rearrange during polymer formation, but the number of each kind of atom in both reactants and products is the same. 24 Excerpt from the Chemistry Content Story Line Sequence of Ideas for Chapter 2 In chemical reactions, the mass of the products is always the same as the mass of the reactants, because atoms are not created or destroyed. If the measured mass of the products is less than the measured mass of the reactants, then some matter/atoms must have left the system. This can occur if a gas is produced and is able to leave the system. If the measured mass of the products is greater than the measured mass of the reactants, system. This can occur if a gas is a than some matter/atoms must have entered the reactant and is able to enter the system. 25 Excerpt from the Biochemistry Content Story Line Sequence of Ideas for Chapter 3 As living things grow, they increase in size and mass because their bodies are making new materials. Even when an entire organism doesn’t appear to be getting any bigger, new materials are still being made. Animal-based foods, and the animals themselves, are made up mostly of proteins. Animals use proteins from food to make the proteins that make up their body structures. Proteins are polymers made up of amino acid monomers. Nearly all proteins can be made from 20 different amino acid monomers, which are made up mostly of carbon, hydrogen, oxygen, and nitrogen atoms. Different proteins are composed of different amounts of the amino acids. During chemical reactions in the digestive tract, proteins are broken down to amino acids. During the break down of proteins to amino acids, atoms are not created or destroyed, just rearranged. Animals use the amino acids to build proteins that make up their body structures. When an animal grows, the number of protein polymers making up its body increases. During the chemical reactions involved in animal growth, atoms are not created or destroyed, just rearranged. As the number of atoms making up an animal’s body increases, the number of atoms in its surroundings decreases. 26 Excerpt from the Biochemistry Content Story Line Sequence of Ideas for Chapter 4 Plant-based foods, and the plants themselves, are made up mostly of carbohydrates. Plant seeds have higher amounts of proteins and fats compared to plant body structures such as leaves, stems, and roots. The carbohydrates that make up most plant body structures are polymers made from glucose monomers, which are composed of C, H, and O atoms. During chemical reactions, plants use glucose monomers to make carbohydrate polymers and water molecules. When plants make carbohydrate polymers from glucose monomers atoms are not created or destroyed, just rearranged. Plants make glucose monomers from carbon dioxide molecules in the air and water molecules. (Because the C and O atoms making up carbohydrate polymers come from CO2, most of a plant’s mass comes from CO2 in the air). During the chemical reactions involved in plant growth, atoms are not created or destroyed, just rearranged. As the number of atoms making up a plant’s body increases, the number of atoms in its surroundings decreases. Plants make amino acid monomers from glucose and a source of nitrogen atoms (from the soil). Like animals, plants use the amino acid monomers to make protein polymers and water molecules. When plants make amino acids, atoms are not created or destroyed, just 27rearranged. Core Ideas (From NRC Science Framework) PS1.B: Chemical Reactions Many substances react chemically with other substances to form new substances with different properties. This change in properties results from the ways in which atoms from the original substances are combined and rearranged in the new substances. However, the total number of each type of atom is conserved in any chemical process, and thus mass does not change either... (grade 8) Understanding chemical reactions and the properties of elements is essential not only to the physical sciences but also is foundational knowledge for the life sciences and the earth and space sciences. 28 LS1.C: Organization for Matter and Energy Flow in Organisms Plants, algae, and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use. Animals obtain food from eating plants or eating other animals. Within individual organisms, food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecules, to support growth, or to release energy… (Grade 8) The sugar molecules thus formed [in photosynthesis] contain carbon, hydrogen, and oxygen; their hydrocarbon backbones are used to make amino acids and other carbon-based molecules that can be assembled into larger molecules (such as proteins or DNA), used to form new cells. (Grade 12) 29 Scientific Practices (From NRC Science Framework) Developing and Using Models Represent and explain phenomena with multiple types of models and move flexibly between model types when different ones are most useful for different purposes. Constructing Explanations Construct explanations of phenomena using knowledge of accepted scientific theory and linking it to models and evidence. Engaging in Argument from Evidence Recognize that the major features of scientific arguments are claims, data, and reasons and distinguish these elements in examples. 30 Crosscutting Concepts (From NRC Science Framework) Systems and system models Defining the system under study—specifically its boundaries and making explicit a model of that system—provides tools for understanding and testing ideas that are applicable throughout science and engineering. Energy and Matter: flows, cycles, and conservation Tracking fluxes of energy and matter into, out of, and within systems helps one understand the systems’ possibilities and limitations. 31