Week 3: Week 3 Content
Grade 7 Science | Rosche | Kairos Academies
Scientists Like Us: In this lesson, you'll work as a team of scientists investigating how energy flows in chemical reactions. Every scientist brings unique perspectives—your ideas matter!
Community Connection: This phenomenon affects our community because understanding reaction energy helps us understand everything from cooking to medicine to staying warm or cool. You'll investigate how scientists use evidence to understand energy transfer in places like ours.
Progress Checkpoint: You've completed Week 1 (Evidence) and Week 2 (Conservation). Next up: Molecular Structure (Week 4).
Pair-Share: First, think about what makes hot packs and cold packs work on your own (1 min). Then share with your partner (2 min). Finally, we'll discuss as a class.
Accessibility & Learning Support
- Need text read aloud? Chrome: Right-click then "Read aloud" | Edge: Click speaker icon in address bar
- Working from home? Look for the HOME ALTERNATIVE boxes at each station
- Need extra support? Click the green "Need help?" buttons for hints and sentence starters
- Stuck? Look for the red "Stuck?" boxes with step-by-step help
NGSS Standards Covered This Week
MS-PS1-6 (Primary)
What it means: Undertake a design project to construct, test, and modify a device that either releases or absorbs thermal energy by chemical processes.
In student language: I can design a device (like a hot pack or cold pack) that uses chemical reactions to release or absorb heat.
3-Dimensional Learning
| Dimension | What You'll Practice |
|---|---|
| SEP-6 Constructing Explanations & Designing Solutions | Design a thermal device using reaction energy principles |
| DCI PS3.D Energy in Chemical Processes | Chemical reactions release or absorb thermal energy |
| CCC-5 Energy and Matter | Energy is stored in chemical bonds; matter is conserved |
Success Criteria - How You'll Know You've Got It
⭐ Target 1 (CRITICAL): Explain that breaking bonds REQUIRES energy (does NOT release energy)
Self-check: Can I explain why photosynthesis needs sunlight to break bonds in CO₂ and H₂O?
Target 2: Explain that forming bonds RELEASES energy
Self-check: Can I explain why hot packs get hot when new bonds form?
Target 3: Classify reactions as exothermic or endothermic
Self-check: Can I tell if a reaction releases or absorbs energy by looking at an energy diagram?
Why This Matters to YOU:
Chemical reactions power your life! Your body uses exothermic reactions (cellular respiration) to release energy from food and keep you warm. Athletes use instant hot packs and cold packs to treat injuries. Understanding bond energy helps you understand everything from cooking (endothermic - needs heat input) to combustion (exothermic - releases heat). This is the foundation of how energy flows through our world!
The Phenomenon: Hot Packs vs. Cold Packs
Consider this puzzling observation:
- Instant hot packs contain chemicals that, when mixed, get HOT (exothermic reaction)
- Instant cold packs contain chemicals that, when mixed, get COLD (endothermic reaction)
- Both involve chemical reactions (evidence: temperature change from Week 1)
- Both conserve atoms (from Week 2), but energy flow is OPPOSITE
Where does the energy come from in hot packs? Where does it go in cold packs?
Focus Question: Why do hot packs get hot but cold packs get cold?
Learning Targets
By the end of this week, you will be able to:
Vocabulary
Cognate Strategy: Many science words look similar in English and Spanish — use your Spanish to learn science!
| Term | Spanish | Definition |
|---|---|---|
| exothermic | exotérmico | Reaction that releases energy to surroundings (gets hot) |
| endothermic | endotérmico | Reaction that absorbs energy from surroundings (gets cold) |
| bond energy | energía de enlace | Energy stored in chemical bonds between atoms |
| activation energy | energía de activación | Energy needed to start a chemical reaction |
| energy diagram | diagrama de energía | Graph showing energy changes during a reaction |
| surroundings | — | Everything outside the reaction system |
| net energy change | cambio neto de energía | Total energy released or absorbed in reaction |
| Exothermic | Exotérmico | Reacción que libera energía al entorno / Reaction that releases energy to surroundings |
| Endothermic | Endotérmico | Reacción que absorbe energía del entorno / Reaction that absorbs energy from surroundings |
| Bond Energy | Energía de Enlace | Energía almacenada en enlaces químicos entre átomos / Energy stored in chemical bonds between atoms |
| Activation Energy | Energía de Activación | Energía necesaria para iniciar una reacción / Energy needed to start a reaction |
| Energy Diagram | Diagrama de Energía | Gráfico que muestra cambios de energía / Graph showing energy changes |
| Surroundings | — | Entorno |
| Net Energy Change | Cambio Neto de Energía | Energía total liberada o absorbida / Total energy released or absorbed |
Worked Example
Step-by-Step Problem Solving
Problem Scenario
Review the problem scenario and work through each step below.
Meet the Scientist: Irving Langmuir
Irving Langmuir (1881-1957) was an American chemist who won the 1932 Nobel Prize in Chemistry for his work on surface chemistry and chemical bonding. He revolutionized our understanding of how atoms bond together and how much energy is involved in forming and breaking those bonds.
The Discovery: Langmuir discovered that atoms form bonds by sharing electrons, and the strength of these bonds determines how much energy is required to break them. He measured bond energies for hundreds of molecules, creating the foundation for understanding exothermic and endothermic reactions. His work showed that different bonds (C-H, O-H, C-O) have different bond energies, which explains why some reactions release more energy than others.
Why This Matters: Langmuir's bond energy measurements allow engineers to design everything from rocket fuels (maximize energy release) to refrigerants (maximize energy absorption). His work on surface chemistry also led to inventions like the gas-filled incandescent light bulb, cloud seeding for weather modification, and improved welding techniques. Understanding bond energies is essential for drug design, materials science, and energy storage!
Connection to Grade 7: In Week 3, you're learning that forming bonds releases energy while breaking bonds requires energy. Langmuir's measurements of specific bond energies (like C-H = 413 kJ/mol, O-H = 467 kJ/mol) allow scientists to predict whether a reaction will be exothermic or endothermic by comparing total energy in vs. energy out!
"The most satisfying thing in life is to have been able to give a large part of one's self to others." - Irving Langmuir
Science in St. Louis: Chemical Manufacturing & Energy
St. Louis companies like Bayer, Sigma-Aldrich, and Mallinckrodt Pharmaceuticals use bond energy principles daily, designing chemical reactions for agriculture, medicine, and materials. Chemical engineers here control exothermic reactions by removing heat and drive endothermic reactions by adding heat—using the exact principles you're learning this week!
Need extra support? Click here for hints and sentence starters
Key Concept Reminder:
- Exothermic: Products LOWER in energy than reactants (energy released to surroundings)
- Endothermic: Products HIGHER in energy than reactants (energy absorbed from surroundings)
- Surroundings: Everything outside the reaction (air, container, your hand)
Sentence Starters:
- "In an exothermic reaction, energy flows _____ because..."
- "I can tell this diagram shows an endothermic reaction because products are..."
- "The surroundings get _____ in an exothermic reaction..."
Word Bank:
exothermic, endothermic, energy released, energy absorbed, products lower, products higher, surroundings, activation energy
Stuck? Click here for step-by-step help
Try these steps in order:
- Look at the energy diagram - find where "Reactants" are labeled (left side)
- Find where "Products" are labeled (right side)
- Compare heights: Are products HIGHER or LOWER than reactants?
- LOWER products = exothermic (energy released), HIGHER products = endothermic (energy absorbed)
- Still stuck? Review the energy diagram table above
COMPLETE THE STATION 1 FORM BELOW
Interpret energy diagrams and classify reactions.
[EMBED G7.C2.W3 Station 1 Form Here]
Form ID: ________________
⭐ Station 2 - Bond Energy Model (CRITICAL MISCONCEPTION)
20 Points | ~15 Minutes
Your Mission: Correct the #1 Misconception
READ THIS CAREFULLY - Refutational Instruction
STEP 1: The Common Misconception
Many students (70-80%!) think: "Breaking chemical bonds releases energy." This seems to make sense because combustion (burning) releases lots of energy and breaks bonds. However, this is BACKWARDS!
STEP 2: The Evidence That Refutes It
Photosynthesis (from Cycle 1 Week 4): Plants NEED sunlight energy to break C-O bonds in CO₂ and H-O bonds in H₂O. If breaking bonds released energy, plants would glow in the dark instead of needing light! This proves breaking bonds REQUIRES energy input.
STEP 3: The Correct Explanation
- Breaking bonds REQUIRES energy input (like pulling apart magnets - you have to PULL)
- Forming bonds RELEASES energy (like magnets snapping together - they release energy)
-
Net energy change determines exo vs. endo:
- Exothermic: Energy released (forming) > Energy required (breaking)
- Endothermic: Energy required (breaking) > Energy released (forming)
STEP 4: Apply to New Context
Hot Packs: The reaction forms new bonds that release MORE energy than was required to break the old bonds. Net result: energy flows OUT to your hand (exothermic, gets hot).
Cold Packs: The reaction requires MORE energy to break old bonds than is released when forming new bonds. Net result: energy flows IN from your hand (endothermic, gets cold).
Memory Tricks for Bond Energy:
- Breaking = "B"reaking apart magnets requires "B"ullying (adding energy)
- Forming = Friends coming together releases happiness (energy)
- Photosynthesis needs light → breaking C-O bonds needs energy input
- If breaking released energy, wood would catch fire without a match!
Need extra support? Click here for more help
Key Concept Reminder:
- Bonds are like glue holding atoms together
- Breaking the glue (bonds) requires PULLING (adding energy)
- When atoms stick together (forming bonds), energy is RELEASED (like a spring snapping)
Sentence Starters:
- "Breaking bonds requires energy because..."
- "Photosynthesis needs sunlight to..."
- "Hot packs get hot because forming new bonds..."
COMPLETE THE STATION 2 FORM BELOW
Answer two-tier diagnostic questions about bond energy.
[EMBED G7.C2.W3 Station 2 Form Here]
Form ID: ________________
Station 3 - Design a Thermal Device
25 Points | ~20 Minutes (Highest Value!)
Engineering Challenge: Hand Warmer OR Ice Pack
Why This Matters - Real-World Application:
- Medical: Instant cold packs treat sports injuries by reducing inflammation and pain
- Outdoor Recreation: Hand warmers keep hikers and hunters comfortable in cold weather
- Emergency Response: First responders use instant hot/cold packs when electricity isn't available
- Food Service: Instant hot packs heat MREs (Meals Ready to Eat) for military and camping
- Your Design Could Save Lives: Understanding bond energy lets you engineer temperature control anywhere!
Design Constraints (You MUST Address):
| Requirement | What You Need to Specify |
|---|---|
| Device Type | Hand warmer (exothermic) OR ice pack (endothermic) |
| Bond Energy Rationale | Which process releases MORE energy: breaking old bonds or forming new bonds? |
| Materials/Reactants | What chemicals will you use? (e.g., calcium chloride + water for exothermic) |
| Safety Consideration | One hazard and how you'll mitigate it |
| Control Mechanism | How will you start/stop the reaction? (e.g., break inner pouch to mix) |
Need extra support? Click here for design hints
Design Tips:
- For hand warmer: Need exothermic reaction (forming bonds releases MORE than breaking requires)
- For ice pack: Need endothermic reaction (breaking bonds requires MORE than forming releases)
- Common exothermic: Calcium chloride + water, iron oxidation (rust)
- Common endothermic: Ammonium nitrate + water
Sentence Starters:
- "I chose to design a [hand warmer/ice pack] because..."
- "This device uses an [exothermic/endothermic] reaction where..."
- "Forming new bonds releases [more/less] energy than breaking old bonds..."
- "One safety hazard is ___ which I'll mitigate by..."
COMPLETE THE STATION 3 FORM BELOW
Design your thermal device and justify your choices!
[EMBED G7.C2.W3 Station 3 Form Here]
Form ID: ________________
Exit Ticket - Bond Energy Mastery
23 Points | ~15 Minutes
Show What You Learned
Question Structure:
- 2 NEW - Bond energy (breaking vs. forming), exo/endo classification
- 2 SPIRAL - Conservation of mass from Week 2 (atoms are conserved, energy is in bonds)
- 1 INTEGRATION - Synthesize bond energy + conservation of atoms
- 1 SEP-6 - Evaluate thermal device designs using bond energy principles
⭐ Critical Success Criterion:
You MUST correctly explain that breaking bonds REQUIRES energy (not releases). This is essential for Cycle 3 success (greenhouse effect requires understanding that IR photons provide energy to vibrate/break bonds).
COMPLETE THE EXIT TICKET BELOW
This is your final assessment for Week 3. Take your time!
[EMBED G7.C2.W3 Exit Ticket Form Here]
Form ID: ________________
Enrichment & Extension
Optional deep dives for early finishers.
Optional content if you finish early or want to go deeper.
Scientist Spotlight
Research a scientist who contributed to this week's topic area and describe their key findings.
Environmental Justice Connection
Explore how this week's science concepts connect to environmental justice issues in our community.