Energy Changes in Chemical Reactions

Contributor
American Chemical Society
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

This is a 5E laboratory lesson plan about endothermic and exothermic reactions. Teaching resources include activity sheets for assessment, answer sheets, a variety of video clips and animations to support the students' learning of the concepts, background information for the teacher, and a test bank.

Intended Audience

Educator
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 appears to be designed to build towards this performance expectation, though the resource developer has not explicitly stated so.

Comments about Including the Performance Expectation
It will be necessary to explicitly make the connections between the definitions of “chemical reaction” and “endo- and exothermic reactions.” Students can know that a new substance is produced without really thinking about bonds being broken and reformed. As such, you could be quite purposeful in highlighting the fact that during a chemical reaction, bonds are broken between the atoms in the reactants. The atoms rearrange themselves and then new bonds are formed. This process of bonds breaking to dissemble the reactants and new bonds forming to assemble the product is how a new substance is formed during the chemical reaction. It takes energy to break those reactant bonds, to dissociate those atoms from each other, but energy is released when bonds are made between atoms during the formation of the product. Depending on the atoms involved in the particular chemical reaction, sometimes the amount of energy needed to break the bonds is more than the amount of energy released when the new bonds are formed. These types of reactions that require energy are known as endothermic reactions. Other times, the amount of energy needed to break the bonds of the reactants is less than the amount of energy that gets released when the products are formed through the making of new bonds. These reactions that release energy are called exothermic reactions. This lesson can also be a good "bridge activity" , acting as an entry point to the concepts needed for standard MS-PS-1-6, "Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes."

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 students will conduct reactions that result in temperature increases as well as decreases. They then need to be able to interpret what those changes in temperature tell them about what is going on with the atoms in the chemical reactions. The idea of perspective is really important here as they make this determination. What is it that they are taking the temperature of, exactly? Is it the atoms and molecules that are reacting, or is it their surroundings? This can be a tricky point for students to understand. You might have students draw simple pictures of their experimental set up, including the beaker, thermometer, circles to represent the reacting particles and, most importantly, the water the particles are dissolved in. Then, have the students draw arrows to indicate if energy is going into or out of the particles during the reaction. These pictures can help them see, for example, that if energy is leaving the particles as the product forms, then the energy goes out into the solution. As such, the temperature of the solution goes up. This is also a great opportunity to have students practice making arguments from evidence.

Disciplinary Core Ideas

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

Comments about Including the Disciplinary Core Idea
Though the ideas are mentioned in the teacher materials and questions for the students, explicitly guiding your students through making the connections between the definitions of “chemical reaction” and “endo- and exothermic reactions” really ties together the Performance Expectation, Practice, and Core Idea for this activity. Students can know that a new substance is produced without really thinking about bonds being broken and reformed. As such, you could be quite purposeful in highlighting the fact that during a chemical reaction, bonds are broken between the atoms in the reactants. The atoms rearrange themselves and then new bonds are formed. This process of bonds breaking to dissemble the reactants and new bonds forming to assemble the product is how a new substance is formed during the chemical reaction. It takes energy to break those reactant bonds, to dissociate those atoms from each other, but energy is released when bonds are made between atoms during the formation of the product. Depending on the atoms involved in the particular chemical reaction, sometimes the amount of energy needed to break the bonds is more than the amount of energy released when the new bonds are formed. These types of reactions that require energy are known as endothermic reactions. Other times, the amount of energy needed to break the bonds of the reactants is less than the amount of energy that gets released when the products are formed through the making of new bonds. These reactions that release energy are called exothermic reactions.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The energy difference between what was needed to break the reactant bonds and what was released when the product bonds were formed can be tracked through the reaction beaker (our system) via measuring the temperature. If the temperature of the solution in the beaker goes down, that means that the reaction absorbed energy from its surroundings (the water molecules) during the chemical change. In other words, the amount of energy needed to break the reactant bonds was more than the amount of energy released from forming the product bonds. As such, energy was absorbed from the surrounding water molecules to complete the reaction. This results in a decrease in the temperature in the beaker for an endothermic reaction. The exact opposite holds true for an exothermic reaction. In that case, the amount of energy absorbed in order to break the reactant bonds is less than the amount of energy released from forming the product bonds. As such, the excess energy is released into the surrounding water molecules and the temperature in the beaker increases. In this way, temperature changes allow us to track energy flow in the system. This crosscutting concept is fundamental to this activity and is addressed in a question for the students to answer. Students may find a more step-wise approach as described above to be helpful in making all the connections necessary in order to answer the energy flow question.

Resource Quality

  • Alignment to the Dimensions of the NGSS: The lab lesson aligns with the letter and spirit of the NGSS. Grade‐appropriate elements of the science practice, disciplinary core idea, and crosscutting concept work together to support students in three‐dimensional learning to make sense of endothermic and exothermic chemical reactions.

  • Instructional Supports: This resource engages students in authentic and meaningful scenarios that reflect the practice of science as experienced in the real world and it provides students with a purpose (e.g., making sense of endothermic and exothermic chemical reactions). The context, including phenomena, questions, and problems, motivates students to engage in three‐dimensional learning. This activity provides students with relevant phenomena, provides opportunities for students to connect their explanation of a phenomenon to their own experience, and uses scientifically accurate and grade‐appropriate scientific information, phenomena, and representations to support students’ three‐dimensional learning. This resource does identify and build on students’ prior knowledge. Further, its provide opportunities for students to express, clarify, justify, interpret, and represent their ideas and respond to peer and teacher feedback orally and/or in written form as appropriate to support student’s three‐dimensional learning. This resource does not currently engage students in multiple practices, though it certainly could with the inclusion of, for example, questions that encourage argumentation from evidence and/or requiring the students to communicate their findings to others (classmates, younger and/or older students in other classes, the principal, at a science night for their parents, etc). It also currently does not include engineering performance expectations or provide guidance for teachers to support differentiated instruction in the classroom so that every student’s needs are addressed.

  • Monitoring Student Progress: This resource elicits direct, observable evidence of three‐dimensional learning by students using practices with core ideas and crosscutting concepts to make sense of phenomena. Formative assessments of three‐ dimensional learning are embedded in the form of questions to be answered as students progress through the activity. This resource does include a test bank (with answers) containing multiple choice, true/false, fill in the blank, and short answer questions. It does not, however, currently include aligned rubrics and scoring guidelines that provide guidance for interpreting student performance along the three dimensions to support teachers in (a) planning instruction and (b) providing ongoing feedback to students. It also does not currently provide for assessing student proficiency using methods, vocabulary, representations, and examples that are accessible and unbiased for all students.

  • Quality of Technological Interactivity: The videos and animations of reactions included with the lab are purposeful and directly related to learning. They do not, however, provide an individualized learning experience. It is really helpful, though, to be able to select particular reactant or product molecules and see (via arrows) the energy going into or flowing out of them. The materials also include answer keys that provide sufficient guidance for interpreting student performance.