Students' conceptual understanding of chemical reactions is foundational to much science learning. Understanding atomic level reactions is crucial for learning physical, life, earth, and space science. Even more importantly, they open up new windows of curiosity for students to see the world around them. By seventh grade, students are ready to take on the abstract nature of the interactions of atoms and molecules far too small to see.
To pique students’ curiosity and anchor the learning for the unit in the visible and concrete, students start with an experience of observing and analyzing a bath bomb as it fizzes and eventually disappears in the water. Their observations and questions about what is going on drive learning that digs into a series of related phenomena as students iterate and improve their models depicting what happens during chemical reactions. By the end of the unit, students have a firm grasp on how to model simple molecules, know what to look for to determine if chemical reactions have occurred, and apply their knowledge to chemical reactions to show how mass is conserved when atoms are rearranged.
Embedded in this unit are a variety of assessments, including self, peer, formative, and summative assessment tasks. This unit concludes with a transfer task in which students apply what they have figured out to two different related phenomena, elephant’s toothpaste and the crumbling of the marble that makes up the Taj Mahal.
Additional Unit Information
This unit builds toward the following NGSS Performance Expectations (PEs):
- MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures. [Clarification Statement: Emphasis is on developing models of molecules that vary in complexity. Examples of simple molecules could include ammonia and methanol. Examples of extended structures could include sodium chloride or diamonds. Examples of molecular-level models could include drawings, 3D ball and stick structures, or computer representations showing different molecules with different types of atoms.] [Assessment Boundary: Assessment does not include valence electrons and bonding energy, discussing the ionic nature of subunits of complex structures, or a complete description of all individual atoms in a complex molecule or extended structure is not required.]
- MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. [Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.] [Assessment boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.]
- MS-PS1-5: Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved. [Clarification Statement: Emphasis is on law of conservation of matter and on physical models or drawings, including digital forms, that represent atoms.] [Assessment Boundary: Assessment does not include the use of atomic masses, balancing symbolic equations, or intermolecular forces.]
The following PE will be developed over three OpenSciEd units; OpenSciEd Unit 6.1: Why do we sometimes see different things when looking at the same object? (One-way Mirror Unit), OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit), and OpenSciEd Unit 8.2: How can a sound make something move? (Sound Unit). This unit will address only the chemical inputs that transmit signals to the brain through smell. The other units will address electromagnetic and mechanical inputs, as well as the connection to signals processing in the brain, resulting in immediate behaviors or memories.
- MS-LS1-8. Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. [Assessment boundary: Assessment does not include mechanisms for transmission of this information]
- MS-LS1.D: Information Processing: Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behaviors or memories.
PS1.A: Structure and Properties of Matter
- Substances are made from different types of atoms, which combine with one another in various ways.
- Atoms form molecules that range in size from two to thousands of atoms.
- Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals).
- Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.
PS1.B: Chemical Reactions
- Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.
- The total number of each type of atom is conserved, and thus the mass does not change.
LS1-D: Information Processing
- Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behaviors or memories.
Disciplinary Core Ideas are reproduced verbatim from A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. DOI: https://doi.org/10.17226/13165. National Research Council; Division of Behavioral and Social Sciences and Education; Board on Science Education; Committee on a Conceptual Framework for New K-12 Science Education Standards. National Academies Press, Washington, DC. This material may be reproduced and used by other parties with this attribution. If the original material is altered in any way, the attribution must state that the material is adapted from the original.
While this unit engages students in multiple SEPs across the lesson level performance expectations for all the lessons in the unit, there are three focal practices that this unit targets to support students’ development in a learning progression across the 7th grade year for the SEPs. These are:
- Constructing Explanations and Designing Solutions
- Analyzing and Interpreting Data
- Engaging in Argument from Evidence
In addition, there are two supporting practices that students will utilize over the course of the unit. These practices are two that students have developed over the course of 6th grade in the OpenSciEd sequence and will be used as supporting practices in this unit:
- Developing and Using Models
- Planning and Carrying Out Investigations
While this unit engages students in multiple CCCs across the lesson level performance expectations for all the lessons in the unit, there are four focal practices that this unit targets to help support students’ development in a learning progression across the 6th grade year in CCCs. These are:
- Scale, Proportion, and Quantity
- Energy and Matter
The bolded sections of the related common core math standards are ones that students engage in.
Density is a property that students measure, graph, and calculate from mass and volume data in Lesson 8. They will be using the following two math concepts in that lesson:
- CCSS.MATH.CONTENT.7.RP.A.2.A Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin.
- CCSS.MATH.CONTENT.7.RP.A.2.B Identify the constant of proportionality (unit rate) in tables, graphs, equations, diagrams, and verbal descriptions of proportional relationships.
Because this unit is taught using a conceptual approach to developing a model of matter that requires the existence of compound particles and smaller constituent parts (atoms), pre-teaching the idea that atoms exist and that they make up molecules is counterproductive to the trajectory of this unit. Students may have heard of the words “atoms” and “molecules” in other contexts and should be encouraged to try to apply any ideas about the particulate nature of matter they may bring to the table in the first part of the unit. But, since OpenSciEd units in 6th grade develop a particulate model of matter that doesn’t distinguish between molecules and atoms, the middle of this unit will be the first time that students will find the need for such distinction based on something they can’t explain about the anchoring phenomena. Many subsequent units in 7th grade OpenSciEd will use the ideas developed in this unit, to explain other phenomena, and will rely on the development of the following ideas developed in this unit. The unit that requires each idea listed here is identified in parentheses.
- Every substance has characteristic properties that can be used to identify it (e.g., solubility, odor, melting point, boiling point, flammability, density, color). These do not change regardless of the amount of the substance. (7.2, 7.3)
- Substances are made from different types of atoms, which combine with one another in various ways. The number, type, and arrangement of atoms in the molecules that make up a substance are unique to that substance. (7.2)
- Atoms form molecules. (7.2, 7.3, 7.4)
- In a chemical reaction, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants. (7.2, 7.3, 7.4)
- In a chemical reaction, the total number of each type of atom is conserved, and thus the mass does not change. (7.2, 7.3, 7.4)
- There are two ways to break apart matter—physical processes and chemical processes. (7.3, 7.4)
- Chemical processes involve the rearrangement of particles that make up the matter; this includes chemical reactions, phase changes, and dissolving. (7.2)
- Dawn Novak, Unit Lead, BSCS Science Learning
- Michael Novak, Field Test Unit Lead, Northwestern University
- Holly Hereau, Writer, BSCS Science Learning
- Gail Housman, Writer, Northwestern University
- Betty Stennett, Writer, BSCS Science Learning
- Keetra Tipton, Writer, Sunset Ridge School, Northfield, IL
- Wayne Wright, Writer, BSCS Science Learning
- Renee Affolter, Reviewer, Boston College
- Tyler Scaletta, Pilot Teacher, Alcott College Prep Elementary School, Chicago Public Schools
- Katie Van Horne, Assessment Specialist
- Joseph Krajcik, Unit Advisory Chair, Michigan State University
- Michael Clinchot, Teacher Advisor, John D. O’Bryant School of Mathematics and Science
- Brian MacNevin, Teacher Advisor, Northwest Educational Service District 189
BSCS Science Learning
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An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has earned the highest score available and has been awarded the NGSS Design Badge. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.