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11 18 Unit 4 Lesson 6

Learning Objectives:

Discover how energy is transferred during a chemical reaction Describe the process of breaking bonds and forming bonds through collisions and energy Discover how energy is transferred during a chemical reaction Analyze how bonds breaking and bonds forming contributes to the overall energy released (exothermic) or absorbed (endothermic) in a chemical reaction Determine if energy is absorbed or released when bonds form and when bonds are broken Warm-up:

Attendance

Open Student IMT Unit 4, make sure lesson 5 is complete. Write down the question for the day and complete the wonderings section for Lesson 6.

IN-CLASS WORK:

Open L4.6 student sheet, make sure the last lesson is updated.
Review L4.6 and complete all parts of the IMT for lesson 6. OUT-OF-CLASS WORK:

Open IMT for Unit 4 and make sure all sections for lesson 6 are complete. Make sure student sheet L4.6 is complete. Complete L4.7 homework assignment (posted in schoology) over break and review lessons 1-6, we will continue with this unit after break then a reminder the unit test will be on the day of the final

L4.6 Student Sheet

Lesson 4.6:  How is energy related to the bonds in a chemical reaction?

RECAP

  1. Debrief as needed ‘Investigating Energy in Other Processes’ - Results/Analysis Questions 7-12

  2. The last two labs helped us figure out that particles rearrange during chemical reactions and that this can result in an increase OR decrease in temperature. 

    1. What are your current ideas about how energy changes when bonds are made or broken? When bonds are made, they typically take less energy then when broken.
    2. How might this connect to reactions heating up or cooling down?

  3. Today we will model what is happening when particles are rearranging to help us explain the changes we are seeing in energy.” How might this help us figure out why hydrogen has such a high energy output compared to gasoline?

OUR INVESTIGATION ON THE ENERGY IN BONDS USING MAGNETIC MARBLES

  1. We will use the set-up above to physically model energy changes associated with bond making and bond breaking. Play with the system and answer the following about the model:
    1. What represents the atoms? The marbles!
    2. What represents the bond? The magnetic attraction between the marble and the magnet
    3. Where is the kinetic energy? The angle of the ruler
    4. In your set-up, what action or movement represents bonds When the marble and the other part have
    5. In your set-up, what action or movement represents bonds breaking? Separating the magnet and the marble

INVESTIGATION PART 1

  1. Record Observations:

    1. Form a bond between two atoms and take note of the change in energy in the model. Record your observations in the chart below.

    2. Break a bond between two atoms and take note of the change in energy in the model. Record your observations in the chart below.

Observations

Formation of a Bond

Breaking a Bond

ANALYSIS AND INTERPRETATION

  1. Think about the speed, movement and energy of the marble. 

    1. What happens to the speed of the marble as it approaches the stationary center marble/magnet when the bond is formed? (Review this video as needed)

    2. There is an increase in kinetic energy during bond formation.  What observation did you make to show that energy was released?

    3. When energy is released is that an endothermic or exothermic process?

    4. What observation did you make to show that energy is required when a bond is broken?

    5. When energy is required is that an endothermic or exothermic process?

    6. A system where the bond was broken by a collision with another atom was filmed in slow motion.  Watch the following two videos:  11 block video and 12 block video

      1. What is happening to the energy as the height of the tower increases?
      2. What happened when the bond was broken?
      3. What are some possible ways that you could break the bond if the magnet was stronger?
      4. Would a stronger magnet require more energy?
      5. If the magnet was stronger, what would that represent in our model?

  2. Describe what is happening with the graphs below.  Write one sentence for what is happening with the speed of the marble during breaking bonds.  Write one sentence for what is happening with the speed of the marble during making bonds.

  3. We have been physically manipulating our models and putting energy into the system to rearrange particles. However, we know that realistically atoms are too small to be manipulated and rearranged in this way and therefore our current model is limited in its accuracy. 

    1. How do atoms normally move and interact? (Hint: Do they move on a ruler track?)
    2. Is a collision necessary to form a bond? Why or why not?

  4. Watch video and summarize what happens during bond maing and breaking in one sentence.

  5. Read the section Potential Energy Diagrams in your textbook and answer the following questions.

    1. In an endothermic reaction, is the potential energy of the products higher or lower than the potential energy of the reactants?
    2. In an exothermic reaction, is the potential energy of the products higher or lower than the potential energy of the reactants?
    3. What does activation energy tell us?

NEXT STEPS:

  1. Reflect on today’s question: Can we model what is happening when particles are rearranging to help us explain the changes we are seeing in energy?

  2. Open up the IMT for this unit, complete all boxes for lesson 6

  3. Make sure all parts of the L4.6 student sheet are complete & complete the check for understanding on schoology.**

Last update: June 5, 2023
Created: June 5, 2023