7th Grade - Unit 1: Chemical Reactions

Instructional Sequence

Assessment Types at
This Stage

Assessment Description

Learning Target

Engage

Predictions, Observations, and Initial Claims: Through a demonstration and activity, students’ background knowledge about substances is elicited. Also, students begin to explore how to distinguish between substances with similar appearances. 

Students observe the physical properties of substances that are similar in appearance to help them later determine if a new substance is formed when substances are combined (i.e., chemical reactions). Students make predictions and observe what happens when copper (II) chloride solution reacts with aluminum foil. Students then propose an evidence-based claim about whether the combination of copper (II) chloride solution and aluminum foil generates a new substance.  

Students should be able to

• Investigate different samples of matter to try to determine if the samples are made of the same or different substances. 
• Record observations from a demonstration in which copper (II) chloride solution is mixed with aluminum foil.
• Use evidence from the demonstration to make a claim about whether or not any new substances were formed when copper (II) chloride solution and aluminum foil are combined.

Explore

Observations and Inferences: 

Through a series of investigations, students observe the results of combining substances that result in either physical changes or chemical reactions. In discussing their observations, students generate a set of criteria for determining whether a mixture of the substances forms (physical change) or a new substance is formed as a result of combining substances (chemical reaction). 

Students investigate what happens when substances are combined. Students make predictions, collect data, and construct evidence-based claims about whether they think a new substance is formed

when they combine two or more substances. Students determine if there is a change in properties and if a new substance forms when they combine substances.  

Students should be able to

• Safely follow a protocol to combine substances.
• Observe that a chemical reaction is often accompanied by changes in color, temperature, and odor/smell.
• Use data to determine if a new substance results from the combination of substances.

Explain

Reading, Group Discussion, and Written Responses: 

Students read an article about substances, physical and chemical properties of substances, and chemical reactions in substances. Students then use information from the article to explain the results of their investigations from a previous lesson (Explore). Students develop a model to help determine whether a combination of substances results in a physical change or chemical reaction.

Students apply information from a reading to analyze their observations from the previous lessons (Engage and Explore). In doing so, students develop a set of criteria to determine if any of the substance combinations results in a chemical reaction, and what constitutes a chemical reaction as opposed to a physical change.

Students should be able to 

• Explain the difference between physical changes and chemical reactions.
• Reflect on observations from the Engage and Explore lessons to determine if a physical change or chemical reaction  occurs. 

Elaborate

Applying Understanding to a New Context: Students apply their ideas (model) from the previous lesson (Explain) to determine whether the rust formation on the Golden Gate Bridge represents a physical change or a chemical reaction.

Students consider the case of the Golden Gate Bridge and why it must be constantly repainted to maintain its distinctive color. Using the Claim, Evidence, Reasoning framework, students decide whether the rusting paint on the bridge  constitutes a physical change or a chemical reaction. 

Students should be able to

• Decide whether a novel scenario represents a physical change or chemical reaction based on evidence gathered throughout the subunit.
• Explain that some chemical reactions are rapid and that some, like rusting, are slow.

Evaluate

Engaging in Argument from Evidence, Revising a Model, and Connecting Concepts:

Students will construct evidence-based arguments regarding the observable results of a chemical reaction.

Students will revisit the Subunit Essential Question:  How can we tell when a chemical reaction has occurred? as they revisit and revise their concept maps. Students will connect the idea that during a chemical reaction, two or more substances combine to form a new substance accompanied by characteristic changes in color, odor, and temperature. 

Students construct, communicate, and revise evidence-based arguments about whether mixing substances results in a chemical reaction. Students will revise their concept maps to address the link between thermal energy and chemical reactions. Additionally, students’ progress toward completing the Culminating Projects will be scaffolded. 

Students should be able to

• Develop and revise a model (concept map) using their current understanding of chemical reactions.
• Explain that during a chemical reaction, two or more substances combine to form a new substance with a characteristic change in color, odor, and temperature.

Instructional Sequence

Assessment Types at
This Stage

Assessment Description

Learning Target

Engage

Predictions, Observations, and Initial Claims: Through a demonstration and activity, students’ background knowledge is elicited regarding atoms, and the relationship between atoms (microscopic scale) and the substances they make up (macroscopic scale.) 

To consider how atomic- scale properties of substances (atoms) are important but difficult to directly observe, students observe what happens when pieces of potato are added to clear, colorless mystery liquids: water and hydrogen peroxide. By gathering visible evidence, students realize that though similar in appearance, the two liquids must be different, and therefore may exhibit different characteristics on a smaller scale. Students also discuss how all matter is made up of atoms and that different atoms exhibit different characteristics.

Students should be able to

• Observe and record observations of two mystery liquids. 
• Observe and make observations of what happens when small pieces of potato are added to each liquid. 
• Draw a diagram of what they think these mystery liquids look like from a zoomed-in view.

Explore

Observations and Inferences: 

Students observe class demonstrations and engage with a computer simulation to help understand that 1) different substances are made up of different types and numbers of atoms and 2) the atoms of a substance are not created or destroyed during a chemical reaction. Students engage in discussion to apply their initial ideas about the conservation of matter to explain how matter does not disappear during a chemical reaction, even when visual evidence may suggest otherwise.

Students explore substances at the atomic scale through a variety of methods. First, through a computer demonstration and simulation, students examine evidence supporting the law of conservation of matter: though substances may combine to form new substances, the number and types of atoms remain the same before and after a chemical reaction. Then, by tearing paper into successively smaller pieces and by observing paper burn, students consider the question, “In each process, did any atoms ‘disappear’?” as a way to engage with the idea that matter is conserved. 

Students should be able to

• Observe, through a simulation, that the Mystery Substances from the Engage lesson are made up of the same type but different numbers of atoms. 
• Observe, through a simulation, that in a chemical reaction, the atoms that make up the original substances are rearranged into different molecules that exhibit different properties than those of the original reactants.
• Observe, through a simulation, that in a chemical reaction, the number and type of atoms remain the same before and after the reaction—the law of conservation of matter must hold.
• Consider what happens at the atomic scale when paper is torn into small pieces (physical change) and when paper is burned (chemical reaction).

Explain

Reading, Group Discussion, and Written Responses: 

Students read an article about the elements of the periodic table, how substances are made up of atoms, and how atoms are neither created nor destroyed during a chemical reaction. Students use the law of conservation of matter to explain how the atoms involved in an observed reaction (baking soda and vinegar) can be rearranged but not lost.

Students read an article introducing the elements of the periodic table, how matter is conserved during chemical reactions, and the types of observable changes often associated with chemical reactions. Students also investigate the chemical reaction that occurs when baking soda and vinegar are combined to observe the characteristics of a chemical reaction and reinforce their understanding of the law of conservation of matter. 

Students should be able to

• Use the law of conservation of matter to explain that the total number of each type of atom is conserved in the physical and chemical processes they observe during this lesson.

Elaborate

Connecting Concepts and Providing Feedback: Students return to their Group Culminating Project designs to consider how the law of conservation of matter relates to their device. Students also critique their peers’ designs and revise their own designs based on peer feedback.

Students use evidence from previous lessons to design their devices and to consider whether energy is absorbed or released by the chemical reaction that occurs in their devices. Finally, students practice critiquing and revising their Group Culminating Project designs to improve their device designs.

Students should be able to 

• Explain that in a chemical process, the atoms that make up the original substances are rearranged into different molecules, and therefore when a substance burns, parts of the substance do not disappear, instead, atoms are rearranged to form new substances. 

Evaluate

Using Models to Show Understanding, Revising a Model, and Connecting Concepts: Students explain how the conservation of matter applies to their devices. Students revisit the Subunit Essential Question, “What happens to atoms during a chemical reaction?” as they revisit and revise their concept maps. Students complete their Group Culminating Project and work on and provide feedback on their Patent Application.

Students are asked to explain how the law of conservation of matter relates to the chemical reaction that occurs in their devices. Additionally, students revise the class concept map to address the link between thermal energy and chemical reactions and the law of conservation of matter. Finally, students work on their Group and Individual Culminating Projects for the unit. After completing a Device Handbook that explains how their hot pack or cold pack works, students allow a peer to review their work.  Students are allowed to revise their Device Handbook based on this feedback.

Students should be able to 

• Explain what happens to atoms before and after a chemical reaction has occurred.
• Revise the class concept map to include concepts they learned throughout Subunit 2. 
• Complete their Group and Individual Culminating Projects.
• Review and provide feedback to another student about their Device Handbook.

Desired Results

Overview

Through investigations, students learn to identify when a chemical reaction has occurred and model the change in molecular structure of materials showing that the number and type of atoms (mass) are conserved in a reaction. The Science and Engineering Practices of Developing and Using Models and Analyzing and Interpreting Data are used to show how scientists might model reactions and collect data to show changes. The Crosscutting Concepts of Scale, Proportion, and Quantity; Patterns; and Energy and Matter are important themes necessary for students to understand changes in atomic structure. 

Project Tasks

Connections to Culminating Project Lift-Off: Answer Reflection Questions designed to draw upon students’ prior knowledge of chemical reactions and hot packs and cold packs. 

Connections to Culminating Project Subunit 1: Develop and modify a model explaining that, during a chemical reaction, two or more substances combine to form a new substance accompanied by observable characteristic changes in color and temperature.  

Connections to Culminating Project Subunit 2: Explain how the conservation of matter applies to the hot or cold pack design.

Estimated length of project: 280 minutes

ESTABLISHED GOALS

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.] 

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.]

MS-PS1-6. Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes. 

[Clarification Statement: Emphasis is on the design, controlling the transfer of energy to the environment, and modification of a device using factors such as type and concentration of a substance. Examples of designs could involve chemical reactions such as dissolving ammonium chloride or calcium chloride.] [Assessment Boundary: Assessment is limited to the criteria of amount, time, and temperature of substance in testing the device.]

MS-ETS1-3. Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

MS-ETS1-4. Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.

NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press.

ESSENTIAL QUESTION

How can we combine two substances to make a hot pack or a cold pack?

Students will be able to independently use their learning to

• Develop and use a model to explain how a chemical reaction inside a device causes that device to heat up or cool down.
• Analyze and interpret data on the properties of substances before and after those substances interact to determine whether a chemical reaction has occurred. 
• Use the law of conservation of matter to explain what happens to atoms during a chemical reaction.

Students will know

• The differences between physical changes and chemical reactions.
• That during a chemical reaction, two or more substances combine to form a new substance with a characteristic change in color, odor, and temperature.
• How to use information about the properties of substances to determine if a chemical reaction has occurred. 
• That in any chemical process, mass is conserved. The atoms that make up the original substances are rearranged into different molecules. Atoms do not disappear.
• How to create a model explaining what happens to atoms before and after a chemical reaction has occurred.

Evidence

Assessment Evidence

PERFORMANCE TASK: Designing a device that releases or absorbs thermal energy by chemical processes. At the end of this unit, students work together to design and construct a device that either releases or absorbs thermal energy by chemical processes. Specifically, as a group, students have an opportunity to design and construct a hot pack or cold pack. 

Individual Culminating Project: Device Handbook

In addition to the Group Culminating Project, students work on an Individual Culminating Project. Individually, students develop a Device Handbook explaining the science behind their device. Additionally, each student proposes at least one improvement to their device based on data gathered through testing.

Learning Plan

Subunit 1

In this subunit, students are introduced to chemical reactions by observing the results of combining a solution of copper chloride and solid aluminum. This reaction serves as an anchoring phenomenon as students investigate how physical changes differ from chemical reactions. Throughout the subunit, students make claims and develop models to explain this phenomenon by understanding that

• In a chemical reaction, two or more substances combine to form a new substance that exhibits different properties than the original substances (i.e., different color, smell, boiling/melting point).
• Chemical reactions can absorb energy from their surroundings and feel cold to the touch - or - 
• Chemical reactions can release energy into their surroundings and feel hot to the touch.

The characteristics of a chemical reaction become important as students consider the Subunit Essential Question, How do we know if a chemical reaction has occurred?, and as students continue to design their devices for the Culminating Project.

Subunit 2

In this subunit, students explore chemical reactions at the atomic scale and learn about the conservation of matter. The fact that matter is conserved when a physical change or chemical reaction occurs means that no atoms are created or destroyed in the process. Because of this, the total mass of the starting materials will be the same as the total mass of the end materials in either a physical change or chemical reaction. Additionally, the number and type of atoms in either a physical change or chemical reaction will remain the same before and after the change.

In this subunit, students continue to focus on chemical reactions that occur when two or more substances are combined. In this type of chemical change, the atoms in the starting substances (reactants) rearrange to form new substances (products). During this process, no atoms are created or destroyed. The emphasis throughout this subunit is on the law of conservation of matter and on physical models and drawings that can represent atoms and atom rearrangement. Students do not balance symbolic chemical equations. Instead, they work with models of atoms to show what occurs during a chemical reaction, with a focus on conservation of atoms. During the subunit, students collect and analyze data to develop a model that explains that in chemical reactions

• Matter is neither created nor destroyed.
• The number and type of atoms remains the same.
• The atoms in the starting substances rearrange which results in the formation of new substances.
   

Unit Map

Chemical Reactions

Essential Question: How can we combine two substances to make a hot pack or a cold pack?

Lift-Off and Introduction to the Culminating Project

 Subunit 1: Observing Chemical Reactions

How can we tell when a chemical reaction has occurred?

Engage • Explore • Explain • Elaborate • Evaluate

Subunit 2: Chemical Reactions at the Atomic Scale

What happens to atoms during a chemical reaction?

Engage • Explore • Explain • Elaborate • Evaluate

Group Culminating Project

Building a Hot Pack or Cold Pack

Individual Culminating Project

Device Handbook

 

Course Concepts

+ Foundational Crosscutting Concepts: These concepts are foundational to the understanding of middle school science. They are present throughout the course. Students are expected to continue to apply their knowledge of the concepts to subsequent relevant projects. 

* Focal Crosscutting Concept: This concept is called out consistently in the Teacher Edition and once per subunit in the Student Book. Students will consider the unit project through the lens of this Crosscutting Concept. 

Crosscutting Concept

Unit 1: Chemical Reactions

Unit 2: Geoscience Processes and Earth’s Surface

Unit 3: Ecosystems

Unit 4: Earth’s Natural Resources

Patterns

+

+

+

Cause and Effect

+

+

*

Scale, Proportion, and Quantity

*

+

Systems and Systems Models

Energy and Matter

+

*

Structure and Function

+

Stability and Change

*

+

+
 

Science and Engineering Practices 

+ Foundational Science and Engineering Practices: These practices “carry forward” through the course. Students focus on one of them per unit and are then expected to continue to apply that knowledge to subsequent relevant projects. 

* Focal Science and Engineering Practice: This practice is called out consistently in the Teacher Edition and once per subunit in the Student Book. Students will use this practice to complete the unit project. 

Science and Engineering Practices

Unit 1: Chemical Reactions

Unit 2: Geoscience Processes and Earth’s Surface

Unit 3: Ecosystems

Unit 4: Earth’s Natural Resources

Asking Questions and Defining Problems 

+

Developing and Using Models 

+

*

+

+

Planning and Carrying Out Investigations 

Analyzing and Interpreting Data

*

Using Mathematics and Computational Thinking

Constructing Explanations and Designing Solutions

+

+

+

+

Engaging in Argument from Evidence

*

+

Obtaining, Evaluating, and Communicating Information

*

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.]

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.]

MS-PS1-6 

Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes.* [Clarification Statement: Emphasis is on the design, controlling the transfer of energy to the environment, and modification of a device using factors such as type and concentration of a substance. Examples of designs could involve chemical reactions such as dissolving ammonium chloride or calcium chloride.] [Assessment Boundary: Assessment is limited to the criteria of amount, time, and temperature of substance in testing the device.]

MS-ETS1-3

Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

MS-ETS1-4

Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.

Misconceptions 

Accurate Concept

All chemical reactions happen quickly.

Some reactions occur very slowly, almost imperceptibly slowly. Students observe an oxidation reaction, a rusting nail in water, to see that some reactions are not quick.

Misconceptions 

Accurate Concept

If two substances share one characteristic property, they are the same substance (AAAS Project 2061, n.d.)

From the American Association of the Advancement of Science (AAAS) Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/100/SCM053)

Two similar substances may share one or more properties, but not ALL properties. Therefore, they are not the same substance. Students observe how substances that are similar in appearance react very differently when combined with other substances, indicating that they are not the same substance.   

Shape, length, and width are characteristic properties of a substance.
 

Shape, length, and width are extrinsic properties of substances that can change even as the substance remains the same. 

A chemical reaction occurs when a substance dissolves (Novak et al., 1991; BouJaoude, 1992; Abraham et al., 1994; Ahtee et al., 1998; Stavridou et al., 1998; Valanides, 2000; Eilks et al., 2007)

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/102/SCM020)

Often, a substance dissolving is an example of a physical change in one substance. Students observe that the copper chloride dissolving in water produces no other predicted observable characteristics of a chemical reaction. 

A chemical reaction always happens when two substances are combined together (AAAS Project 2061, n.d.)

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/102/SCM070)

Students see that some combinations of substances produce no noticeable effects. 

All chemical reactions are inherently dangerous (Cavallo et al., 2003).

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/102/SCM037)

Every chemical reaction observed in this unit is safe for students to handle if done using gloves and goggles. The most dramatic reactions will feel warm or cold to the touch but will not result in burning or freezing.

Misconceptions 

Accurate Concept

The atoms of the reactants of a chemical reaction are transformed into other atoms (Andersson, 1986). 

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/99/SCM026)

During a chemical reaction, atoms stay the same but rearrange to form new molecules.

Mass is not conserved during processes in which gases take part (Mas et al., 1987; Berkheimer et al., 1988; Hesse et al., 1992),  For example when gases are produced, the total mass must decrease. 

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/125/SCM029)

In a closed system, when a gas results from a chemical reaction, the total mass and total number of atoms involved in the reaction do not change. 

When a chemical reaction occurs, matter just disappears. For example, during combustion reactions, burning paper, or burning gasoline, fuel is used up and disappears.(Andersson, 1986)

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/125/SCM027)

When a chemical reaction occurs in a closed system (sealed container), the mass of the materials, and the number of atoms involved, stays the same.

New atoms are created during chemical reactions. (AAAS Project 2061, n.d.)

From AAAS Misconceptions (http://assessment.aaas.org/misconceptions/1/SC/126/SCM083)

During a chemical reaction, the number and type of each atom remains the same. However, the atoms are rearranged to form new substances that often give the appearance of new atoms being formed. 

Permanent

Consumable

Teacher Provided

• 400 mL  beaker (5)

• 500 mL beaker (8)
• Graduated cylinder, 100 mL (13)
• Plastic tray - 1” deep 
• 100 mL pyrex beaker (5)
• Nonmetallic thermometer (8)
• Nonmetallic tongs (1)
• Teaspoon (36)
• 250 mL pyrex beaker (8)
• Magnifier, plastic (8)
• 100 mL graduated cylinder
• Tablespoons (16)
• 3 ½ x 1 ¼ rubber bands (1 box)
• Small glass vial (40)
• Vegetable knife (1)
• Poker chips-color 1 (16)
• Poker chips -color 2 (48)
• Poker chips - color 3 (56)
• Lighter or matches
• 3 mL plastic pipette (8)
• Rocks (3 lbs.)
• Sand (4 lbs)

• Iron nail, non-galvanized(5)
• 3% hydrogen peroxide solution (500 mL)
• Potassium iodide solution (25 mL)
• Copper (II) chloride powder (25g)
• Resealable sandwich bags (100)
• Snack-size resealable bags (100)
• 72-box Alka-Seltzer (2 boxes)
• Coarse salt (1 lb.)
• Cornstarch (1 lb.)
• Fine salt (1 lb.)
• 1 oz. medicine cup (250)
• Powdered sugar (1 lb.)
• Granulated sugar (1 lb.)
• Baking soda (10 lbs.)
• Calcium chloride (1000 g)
• White vinegar (3 16 0z. bottles)
• 3 oz. paper cups (280)
• Black construction paper (50 sheets)

• Piece of chart paper (6)
• Large 5"x7" sticky notes (144) 
• Small sticky notes (144) 
• Marker (32) 
• Highlighter (32) 
• Scissors (8)
• tap water (250 mL)
• Potato (1)
• Aluminum foil (400 ft.)
• Dishwashing liquid (50 mL)