Baggie Chemistry

Contributor
The Concord Consortium
Type Category
Instructional Materials
Types
Experiment/Lab Activity
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

Reviews

Description

Students begin the activity by brainstorming observable changes that indicate a chemical change has occurred. They then mix calcium chloride with water and measure the temperature change during the reaction. Next, they add baking soda to the solution and measure the temperature change. Throughout, students are prompted to record observations that indicate a chemical reaction has taken place. They also are asked to analyze the temperature changes and determine if the reactions produced or consumed heat.

Intended Audience

Learner
Educational Level
  • Middle School
Language
English
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

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.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
The activity briefly introduces the concepts of physical and chemical changes, but perhaps doesn't do enough to emphasize the fact that some changes, like a color change, can be either a physical OR a chemical change depending on the circumstances. In these cases, it is important to know what the atoms are doing during the change. Later in the activity, the chemical equation for calcium chloride reacting with sodium bicarbonate is provided so that this point can be made more clearly. Students can analyze the equation to determine that the reactant atoms have rearranged to form new partnerships and thus the change of state from a solid (NaHCO3) to a gas (CO2) is in this case indicative of a chemical change.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
The template for the activity does a nice job of asking students to record a variety of their observations throughout the activity, including snapshots of temperature probe data graphs, and written observations. It isn’t until later in the activity, though, that they are asked “why” questions and encouraged to use that evidence to support their answers to such questions. More analysis questions could be added into the activity earlier on to help support the inclusion of this practice. There also are no directions about how long the answers should be, so one might want to add some specificity there to encourage students to think and write more deeply about what they are observing. Lastly, adding an oral presentation component to the end of the activity so that students can share their results with their classmates will more strongly align this activity with the complete scientific practice.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
The framework for addressing the entire DCI is present in this activity, however, the connections between the components are not made clearly enough as it is currently structured. The chemical equation for the second reaction between aqueous calcium chloride and solid sodium bicarbonate is provided. The students can be guided to analyze this equation to determine if the atoms in the reactants are partnered the same way before and after the reaction. Since they are not, the students can surmise that this is a chemical reaction. A nice addition to this activity may be to analyze an equation for a *physical* change of a solid into a gas. Probably the easiest reagent to use would be dry ice, which one can purchase fairly easily these days. The students can compare and contrast the experimental evidence for both reactions as both show a solid (dry ice or sodium bicarbonate) reacting to form a gas (CO2 in both cases). The students can then analyze the equations to determine if both reactions proceeded in the same manner, i.e., via physical or chemical change. The addition of such an activity and associated analysis questions would more clearly link this resource to the full text of the DCI.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
As with the DCI, the framework for addressing the entire CCC is present in this activity, however, the connections between the components are not made clearly enough as it is currently structured. As written, the activity does not explicitly encourage students to draw connections between their macroscopic observations and the atoms that are reacting. By purposefully guiding students to connect their macroscopic observations of the reactions with the balanced chemical equations that represent what is happening on the atomic level in those reactions, one can more clearly bring this resource in alignment with the CCC. There are a limited number of observations that indicate that chemical changes are occurring. If students recognize the pattern of these indicators, they can understand more clearly what is happening on the atomic level with all kinds of reactions.

Resource Quality

  • Alignment to the Dimensions of the NGSS: In this activity, students use an NGSS practice about engaging in argument, to demonstrate understanding of a disciplinary core idea about chemical reactions. The connection to a cross-cutting standard about patterns is not particularly strong, and will need to be made overt by the teacher. See Teacher Tips in the cross-cutting standard section above. The connections to the practice and disciplinary core idea can also be made even stronger and more overt - see Teacher Tips in those sections above for suggestions. The activity as written is rather formulaic; a teacher could offer opportunities for students to design their own experiments with the given materials.

  • Instructional Supports: This resource engages students in authentic science practices, with a clear purpose (distinguishing chemical reactions from physical changes). The combination of hands-on work, opportunities to use probeware, and reflection in an online format, is an engaging one for students. This resource provides opportunities for students to express, clarify, justify, interpret, and represent their ideas, through the online journal. The resource touches on students’ prior knowledge of the characteristics of a chemical change. This resource does not currently include ideas for differentiation. Teachers might have students work in groups and assign different roles to different students, e.g. probeware operator, journal recorder, group facilitator, etc. A few small photographs are included; more photos or a teacher demo can be useful for students who struggle with reading text. Two of the questions could also provide jumping-off points for more advanced students or groups to develop their own investigations (one question involves conservation of mass, and one question asks about another way that a chemist might conduct the investigation).

  • Monitoring Student Progress: The resource asks students to answer questions, which a teacher can use as a check-in to monitor student progress. The questions do directly relate to the Performance Indicator and Practice, but do not address the complete Disciplinary Core Idea - the questions do not ask students about atoms rearranging to create new substances. A teacher would need to add a question or short activity about this idea. See the Teacher Tips for the DCI, above. The questions also do not address the cross-cutting concept - they do not ask students to explain the way the visible chemical changes are the result of microscopic molecular changes, though a question about conservation of mass could be slightly modified to make that connection clearer. See also the Teacher Tips for the DCI and cross-cutting concept, for ideas about how to include these more strongly in the lesson. This resource currently does not include rubrics, scoring guides, or exemplars.

  • Quality of Technological Interactivity: This activity has several interactive features: online student journals that teachers can access, graphical representations of probeware data, and a “snapshot album” to which students can upload screenshots of data and graphs. The interactive features are purposeful and directly related to learning. The features allow students to choose their own input, but do not “respond”; the features do not change based on user input, but remain the same for everyone. The interactive component is well designed, easy-to-use, and will run on a variety of modern web browsers. Please note that students can only save and share their work if they and the teacher are registered users. Registration is free.