3 (1 reviews)
1 Wasteful
Reviewed by: Sandra Cornelius (Rescue, CA) on 6/19/2019 8:35:23 AM
I did not do this lab, but I CANNOT believe you are promoting performing labs in disposable plastic baggies:(
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.
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.
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.
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.
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.