City Heat Worksheet
Article Investigation Thermal Energy • Molecular Collisions • Urban Systems
How Air Conditioners Make Cities Hotter
Name:
Date:
Period:
1
Molecules, Motion, and Temperature
A. Molecular Speed vs. Temperature
What is the difference in speed and kinetic energy between molecules in warm air vs. cool air?
B. How Air Conditioners Cool Rooms
What do the machines and chemicals in an AC unit do to the kinetic energy of indoor air molecules?
2
Energy Transfer via Molecular Collisions
Key Law: Energy cannot be created or destroyed — only transferred
A. What Happens During a Collision?
Faster (Hot) → bumps into → Slower (Cool)
When a faster molecule bumps into a slower molecule, what happens to the speed and kinetic energy of each molecule?
B. The "Disappearing Heat" Myth
When indoor air cools down, the heat doesn't disappear. Where does that kinetic energy actually go, and what does it do to the outdoor air molecules?
3
The Washcloth Analogy: Connected Systems
A. Direction of Energy Flow
Which direction does energy flow between your feverish forehead and the cool washcloth? Why?
B. Why Washcloths Stop Working
Why does that same washcloth eventually stop cooling your forehead? What happens to their temperatures?
Amplify Science • Thermal Energy Unit Turn to Page 2 → Page 1 of 2
How Air Conditioners Make Cities Hotter
Part 4: Systems Comparison • Part 5: Urban Feedback • Part 6: Scientific Argument (CER)
Name:
4
Comparing Two Thermal Systems
| System Feature | System A: Fever & Washcloth | System B: Building & Outdoor Air |
|---|
| Part of system losing energy (cooling down) | | |
| Part of system gaining energy (warming up) | | |
| Mechanism that connects both parts | Direct contact: molecules bump into each other | |
5
The Urban Feedback Loop
Evidence from Text
“On hot nights when many people run their AC, the temperature outside is about 1°C (1.8°F) hotter than it would be otherwise.”
Explain the Vicious Feedback Cycle:
How does this 1°C outdoor increase trigger a cycle that makes cities progressively hotter and strains energy use?
6
Claim-Evidence-Reasoning: Busting the AC Myth
Use principles & evidence from the text
Myth “Air conditioners destroy heat to make rooms cooler. When the AC is on, thermal energy just vanishes.”
Claim (Directly refute the myth):
Evidence (Data & observations from the article):
Reasoning (Scientific law of energy conservation & molecular collisions):
Amplify Science Aligned • Thermal Energy Unit Assessment • Reading Comprehension Page 2 of 2
City Heat Answer Key
Teacher Answer Key Standards Aligned • Amplify Science Thermal Energy
How Air Conditioners Make Cities Hotter
Total Points: 25 | Passing: 18+ (72%)
1
Molecules, Motion, and Temperature
[4 Points: 2 pts each]
A. Molecular Speed vs. Temperature
Speed and kinetic energy difference in warm air vs. cool air:
Exemplar Response: Temperature is directly caused by the speed of molecules. Molecules in warm air move faster and possess more kinetic energy. Molecules in cool air move slower and possess less kinetic energy.
Look-for: Mentions both speed and kinetic energy.
B. How Air Conditioners Cool Rooms
Effect of AC machines/chemicals on indoor molecules:
Exemplar Response: The AC machines and refrigerants remove kinetic energy from indoor air molecules. This slows the molecules down, which lowers the temperature of the room.
Look-for: Mentions slowing molecules down / removing kinetic energy.
2
Energy Transfer via Molecular Collisions
[6 Points: 3 pts each]
A. What Happens During a Collision?
Faster bumps into slower
Exemplar Response: Kinetic energy transfers from the faster-moving molecule to the slower-moving molecule. As a result, the faster molecule loses energy and slows down, while the slower molecule gains energy and speeds up.
Full credit requires explaining the outcome for BOTH molecules (faster slows, slower speeds up).
B. The "Disappearing Heat" Myth
Exemplar Response: Energy cannot be created or destroyed. The kinetic energy removed from inside molecules doesn't vanish—it transfers to outdoor air molecules. Collisions between faster and slower molecules outside speed up the outdoor air, warming up the city.
Key vocabulary: Law of Conservation of Energy, energy transfer, outdoor heating.
3
The Washcloth Analogy: Connected Systems
[5 Points]
A. Direction of Energy Flow
Energy flow direction and scientific reason:
Exemplar Response: Thermal energy flows from the warm forehead to the cool washcloth. When two objects of different temperatures touch, the warmer object's faster molecules collide with and transfer kinetic energy to the cooler object's slower molecules.
Crucial: Energy flows from hot to cold (cold never flows).
B. Why Washcloths Stop Working
Why cooling stops over time:
Exemplar Response: The washcloth absorbs energy and warms up while the forehead cools down until both reach the same temperature (thermal equilibrium). Once molecular speeds equalize, net energy transfer ceases.
