Science Task: Explaining High Altitude Balloon Pops

Instructions

Meteorologists rely on high altitude weather balloons to gather data from the upper atmosphere. Before launch, the balloons are underfilled. As they rise, the air temperature drops drastically. Despite this drop in temperature, the balloons continue to expand until they eventually pop.

In this task, you will use the Gay-Lussac’s Law Simulation to investigate how temperature affects gas pressure in a fixed volume, and then use your findings to explain why dropping temperatures might not be the primary factor in why weather balloons expand and pop.

Part 1: Investigating Gay-Lussac’s Law

1. Open the Gay-Lussac’s Law Simulation.
2. Adjust the Temperature slider and observe the behavior of the gas particles. What happens to the speed of the particles as temperature increases?
3. Look at the Pressure vs. Temperature graph. What type of relationship exists between Temperature and Pressure when Volume is held constant? (e.g., direct, inverse, exponential). Use evidence from the simulation to support your claim.
4. Calculate the constant $k$ for Gay-Lussac’s Law ($P/T = k$) using two different data points from the simulation. Do your calculations confirm the law?

Part 2: Connecting to Macroscopic Energy

1. The NGSS states that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles. Using the simulation as a model, explain how the macroscopic property of “Pressure” is a direct result of the microscopic kinetic energy of the individual gas particles.
2. How does increasing the temperature change the frequency and force of collisions between particles and the container walls?

Part 3: The Weather Balloon Phenomenon

1. Gay-Lussac’s Law assumes a fixed volume. A weather balloon is a flexible container. Based on what you learned about particle collisions and pressure, if a balloon was cooled down but allowed to change volume, what would happen to its volume to maintain a constant internal pressure?
2. The atmosphere gets incredibly cold at high altitudes. If temperature were the only factor, a weather balloon should shrink. However, the external atmospheric pressure also drops rapidly at high altitudes. Which factor (the drop in temperature causing a pressure decrease, or the drop in external pressure allowing the gas to expand) has the dominant effect on the balloon? Explain your reasoning using particle collision models.