7. Lesson 7: Making and Breaking Bonds

Carole Namowicz, Shruti Researcher
Chemistry
100 min
High School
v5
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Overview

The following endothermic reaction is demonstrated for students:

2Ba(OH)2 + NH4Cl → 2BaCl2 + NH3 + 4H2O

They will easily identify it as endothermic as the temperature will drop rapidly after the solid reactants are mixed together. Students will answer some introductory questions about breaking and making bonds and what they believe occurred here.

Then students will use paper cut-outs of the atoms involved in the chemical reaction. This will allow them to indicate the initial bonds present in the reactants, to determine which bonds need to break to allow the rearrangement of atoms in the products, and finally what new bonds must be created to form the products. The goal is to determine if more bonds are broken or formed in the overall reaction, and to connect this with the entire reaction being endothermic or exothermic.

Underlying Pages

Standards

Next Generation Science Standards
  •   Physical Science
    • [HS-PS1-4] Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.
    • [HS-PS3-2] Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects)
Computational Thinking in STEM
  •   Data Practices
    • Collecting Data
    • Creating Data
    • Manipulating Data
    • Visualizing Data
    • Analyzing Data
  •   Modeling and Simulation Practices
    • Assessing Computational Models
    • Using Computational Models to Understand a Concept
  •   Systems Thinking Practices
    • Communicating Information about a System
    • Investigating a Complex System as a Whole
    • Thinking in Levels
    • Understanding the Relationships within a System
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