The Expansion of Air: Exploring Charles’s Law - Student Handout

NGSS Alignment: HS-PS3-2

Performance Expectation: 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 and energy associated with the relative position of particles.

Part 1: Engage (Anchoring Phenomenon)

Consider a balloon.

• Cold Nitrogen: Shrivels to a tiny fraction of its size.
• Hot Water: Expands back to full size. The Question: What is happening to the “energy” of the air particles to cause this?

Part 2: Explore (Simulation Investigation)

Open the Charles’s Law Simulator. Track the change in volume as you adjust temperature from 100K to 600K.

Experimental Data Table:

| Trial | Temp (K) | Volume (L) | Ratio (V/T) | | :— | :— | :— | :— | | 1 | 100 | | | | 2 | 300 | | | | 3 | 500 | | | | 4 | 600 | | |

Part 3: Explain (Sensemaking)

1. Macroscopic Pattern: Describe the relationship between Temperature and Volume.
2. Microscopic Mechanism: How does heat energy change individual particle behavior?
3. Logic: Why does the piston move UP when particles move faster?
4. Claim: Support the claim of a proportional relationship using your V/T ratios.

Part 4: Elaborate/Evaluate

1. Kinetic Energy: Which variable (V or T) represents particle motion in this model?
2. Potential Energy: Which variable relates to the relative position of particles?
3. Reasoning: Why must volume increase to keep pressure constant when particles speed up?
4. Prediction: What happens at 0 K (Absolute Zero) according to this law?

Part 5: Summary

How does a hot air balloon work? Use the terms: Kinetic Energy, Particle Collisions, and Density.