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Beginner's Guide to Rockets
Gas Temperature

If so instructed by your teacher, print out a worksheet page for these problems. Materials:

  • 9" balloon
  • 500 ml Erlenmeyer flask (or glass bottle with a mouth small enough for balloon to fit over)
  • boiling water
  • matches
  • laboratory burner

Before you begin: Remember to record observations of the balloon throughout the procedure.

  1. Place water in the flask to cover the bottom (approximately two centimeters). Boil the water for three to four minutes. Wait one minute and pour the water out of the flask. Quickly place an uninflated balloon (just out of the package) around the mouth of the flask, sealing the flask. Let cool.

  2. Compare the temperature of the gas molecules inside the flask with those outside the flask:
    A. before the flask was heated
    B. after the flask was heated
    C. after the balloon was placed on the flask

  3. How does the change in temperature affect:
    A. the gas molecules' motion?
    B. the gas molecules' force?

    Note: To help with this question use the slide on Gas Temperature in the Beginner's Guide to Rockets.

  4. Now click RocketThrust Simulator to note the exit Mach number, exit velocity, and combustion chamber temperature for a typical rocket nozzle. Using other information available on the Thrust Equations Summary page, determine:
    A. What happens to gas temperature as the exhaust travels through the nozzle from the throat to the exit?
    B. How does molecular motion change from the throat to the exit?
    C. What is one function of a rocket nozzle?

  5. What is the relationship between gas temperature and molecular motion? How did you form this conclusion?

  6. What is the relationship between gas temperature and the force of the gas molecules? How did you form this conclusion?

  7. After studying gas temperature and rocket nozzles, list three questions that you or you and your lab partners now have about this topic.

Related Sites:
Teaching Standards
Rocket Index
Rocket Home
Exploration Systems Mission Directorate Home


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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: May 13 2021

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