Chemical Reactions for 7th Grade Chemistry - MS-PS1-1, MS-PS1-2, MS-PS1-5,. MS-LS1-8
Unit Overview

7.1 Chemical Reactions & Matter

How can we make something new that was not there before?

Unit Summary

Seventh grade chemistry students' conceptual understanding of chemical reactions for middle school science 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 7th grade 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 for middle school science. 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.

Additional Unit Information

Next Generation Science Standards Addressed in this Unit

Performance Expectations

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This 7th grade chemistry 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 7th grade unit will address only the chemical reactions that input the 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.

Disciplinary Core Ideas

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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.

Science & Engineering Practices

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While this 7th grade chemistry 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 7th grade chemistry 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

Crosscutting Concepts

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While this 7th grade chemistry unit engages students in multiple CCCs across the lesson level performance expectations for all the lessons in the unit, there are three focal practices that this unit targets to help support students’ development in a learning progression. These are:

  1. Patterns
  2. Scale, Proportion, and Quantity
  3. Energy and Matter

Connections to the Nature of Science

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Which elements of the Nature of Science are developed in the unit?

  • Scientific explanations are subject to revision and improvement in light of new evidence. (NOS-SEP)
  • Science knowledge is based upon logical and conceptual connections between evidence and explanations.(NOS-SEP)
  • Science knowledge is cumulative and many people, from many generations and nations, have contributed to science knowledge. (NOS-CCC)

How are they developed?

  • Students begin developing explanations about where the gas from the bath bomb is coming from, and then they revise those explanations as they gather evidence from their investigations.
  • Students build their science knowledge about chemical reactions based on logical and conceptual connections they make using evidence from their investigations about what happens when a bath bomb is added to water over the course of the unit.
  • Students develop ways to represent what happens during chemical reactions at the molecular level through multiple revisions. They read about how other scientists used this same approach over the years to revise their prior models to help them make sense of a phenomenon as they collect new evidence.

Unit Placement Information

What is the anchoring phenomenon and why was it chosen?

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This unit begins with an exploration of observing what happens when a store bought bath bomb is added to water. Students make observations of the bath bomb multiple times: 1) before adding it to water by passing it around the class, 2) right after the bath bomb has been added to water, and 3) after the bath bomb has been in the water for 10 minutes. They notice that when the bath bomb is added to water it immediately begins to behave differently—it bubbles (forming a gas), breaks apart (dissolves and reacts), changes the color of the water, and has an odor that wasn’t as evident before adding to the water. After observing a store bought bath bomb as a class, each student is given one of four different homemade bath bomb samples to investigate before and after adding to water. These investigations lead to students having many questions about bath bombs and ideas for how to investigate what is causing the different bath bombs to behave the way they do.  

Each OpenScied unit’s anchoring phenomenon is chosen from a group of possible phenomena after analyzing student interest survey results and consulting with external advisory panels. We also chose bath bombs as the anchor for this unit for these reasons:

  • Bath bombs are common, everyday examples of a product that undergoes a chemical reaction. The example ones listed in the clarification statement for MS-PS1-2 (burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride) are not as connected to students’ everyday experiences.
  • The production of bubbles that occurs when bath bombs are added to water would draw on a wider range of students’ own experiences with other related phenomena. These included: Antacid tablets, water purification tablets, mints added to carbonated soda, and baking soda mixed with vinegar.
  • The most prevalent ingredients in bath bombs are household items, that are relatively inexpensive to purchase and can be locally sourced as consumbables for classrooms.
  • The most prevalent ingredients in bath bombs are non-toxic, and therefore allow students an opportunity to work directly with the reactants and products in a chemical reaction, without incurring an unacceptable level of risk if these substances were accidently ingested. This was an important safety consideration, since this unit was the first introduction to working with chemicals in a lab setting in the middle school OpenSciEd program.
  • A pre-field test of the pilot for a bath-bomb based anchor produced driving question boards on which the majority of the students’ questions and ideas for investigations / sources of data needed to answer those questions, were anticipated by the unit development team and were specifically targeted in the field test version of the storyline.

How is the unit structured?

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This unit is broken into two lesson sets, focusing on properties of substances, chemical reactions, and conservation of mass. In the first lesson set, students investigate bath bombs and the ingredients that make up bath bombs to identify different substances in gas form using property data. In the second lesson set, students use property data and conservation of mass to argue whether a chemical reaction has occurred resulting in a new substance.

Where does this unit fall within the OpenSciEd Scope and Sequence?

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This is the first unit in the 7th grade scope and sequence for OpenSciEd. There are six total units designed for 7th grade. This unit directly builds off the Disciplinary Core Ideas (DCIs), Crosscutting Concepts (CCCs), and Science and Engineering Practices (SEPs) developed in two of the 6th grade units that preceded this one. Those two units are: the Cup Design Unit and the Storms Unit. There are three units that follow this unit in 7th grade that will build off the DCIs, CCCs, and SEPs developed in this unit. Those units are: the Homemade Heater Unit, the Inside Our Bodies Unit, Maple Syrup Unit.

What modifications will I need to make if this unit is taught out of sequence?

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Because this 7th grade chemistry 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 7th grade chemistry 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)

What mathematics is required to fully access the unit’s learning experiences?

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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.

How do I shorten or condense the unit if needed? How can I extend the unit if needed?

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The following are example options to shorten or condense parts of the unit without completely eliminating the important sensemaking for students.

  • Lesson 6: This is a mid-unit transfer task where students apply what they have figured out about identifying substances through properties. Students analyze Elephant’s Toothpaste, which is usually one of the related phenomena from Lesson 1, to argue what gas is being created during this investigation. Lesson 5 would be used as a midpoint assessment and this lesson could be skipped.
  • Lesson 13: If short of time, this lesson could be skipped. Usually there will be a category of questions around odors or smells of the bath bombs and why there are different odors so this lesson helps to fully close out the DQB. In addition, the DCI LS1.D is spread across multiple units in OpenSciEd, this being one of them. So if this lesson is skipped during this unit, more time or support might be needed in one of the other units that address this DCI (OpenSciEd Unit 6.1: Why do we sometimes see different things when looking at the same object? (One-way Mirror Unit), OpenSciEd Unit 6.6: How do living things heal? (Healing Unit), OpenSciEd Unit 8.1: Why do things sometimes get damaged when they hit each other? (Collisions Unit), and OpenSciEd Unit 8.2: How can a sound make something move? (Sound Unit)).
  • Lesson 14: By Lesson 12, students will be able to explain the anchor, so this lesson could be dropped if time is short. This lesson provides students the opportunity to apply what they have figured out about chemical reactions to a real world situation, the crumbling and discoloration of the Taj Mahal.

To extend or enhance the unit, consider the following:

  • Lesson 6: This lesson is a transfer task in which students watch two video clips of the Elephant Toothpaste investigation and read second hand data from this investigation. If there is interest and time, this investigation could be done as a demonstration in class. This would allow students to use first hand data and observe this investigation closer up.
  • Lesson 10: If you have the supplies, you could have students work in small groups and conduct the electrolysis investigation with their small group.

Unit Acknowledgements

Unit Development Team

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  • 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

Production Team

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BSCS Science Learning

  • Christine Osborne, Copyeditor, Independent Contractor
  • Denise Rubens, Copyeditor, Independent Contractor
  • Stacey Luce, Editorial Production Lead
  • Valerie Maltese, Marketing Specialist & Project Coordinator
  • Renee DeVaul, Project Coordinator and Copyediting
  • Chris Moraine, Multimedia Graphic Designer

Unit External Evaluation

EdReports

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EdReports awarded OpenSciEd an all-green rating for our Middle School Science Curriculum in February 2023.  The materials received a green rating on all three qualifying gateways: Designed for the Next Generation Science Standards (NGSS), Coherence and Scope, and Usability. To learn more and read the report, visit the EdReports site.

NextGenScience’s Science Peer Review Panel

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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.

ed report
Unit standards

This unit builds toward the following NGSS Performance Expectations (PEs) as described in the OpenSciEd Scope & Sequence:

  • MS-PS1-1
  • MS-PS1-2
  • MS-PS1-5
  • MS-LS1-8
Reference to kit materials

The OpenSciEd units are designed for hands-on learning and therefore materials are necessary to teach the unit. These materials can be purchased as science kits or assembled using the kit material list.

NGSS Design Badge

Awarded: Aug 5, 2020

Awarded To: OpenSciEd Unit 7.1: How Can We Make Something New That Was Not There Before?

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