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### Beginner's Guide to Propulsion Air Temperature Answers

1. Observations:
Students should note that the balloon inflates after being placed on the heated flask.

2. A. Compare the temperature of the gas molecules inside the flask with those outside the flask before heating.
The temperature is the same inside as outside.

B. Compare the temperature of the gas molecules inside the flask with those outside the flask during heating.
The gas molecules inside the flask are at a higher temperature and therefore have a greater average kinetic energy than those outside the flask.

C. Compare the temperature of the gas molecules inside the flask with those outside the flask after the balloon was placed securely on the flask.
With the heat source removed, the gas molecules start to lose their kinetic energy to the surroundings. In so doing the gas molecules gradually slow down. Their average kinetic energy is reduced, and therefore their temperature drops.

3. A. How does the change in temperature affect the gas molecules' motion?
The gas molecules' speed is reduced. Students should also note the consequent reduction in volume after cooling of the gas molecules inside the flask. Hopefully, students can make the connection between increasing temperature with an increase in volume.

B. How does the change in temperature affect the gas molecules' force?
As temperature decreases the gas molecules inside the flask exert a decreasing force on the balloon. The force per unit area (pressure) of the atmospheric gas molecules is relatively constant. Thus there is an unbalanced force acting on the balloon. Remember that SCIENCE DOES NOT SUCK!

4. A. What happens to air temperature as air travels through the engine from stations 0 to 8?
There is an overall increase in temperature.

B. How does molecular motion change from stations 0 to 8?
There is an overall increase in molecular motion.

C. What is one function of a gas turbine engine?
To increase the overall temperature of the air as it passes through the engine.

5. If this engine were functioning at room temperature what would be the temperature of the gas at station 8? Show work.
Room temperature should be measured. Assuming a temperature of 20 degrees Celsius; convert to Kelvin: 20 C + 273 = 293 K. Temperature of the gas at station 8 = 3.5 (293 K) = 1026 K. Convert back to Celsius if you choose; 1026 K -273 K = 753 C.

6. What is the relationship between air temperature and molecular motion?
As molecular motion increases, average kinetic energy increases, and temperature increases.

How did you form this conclusion?
Answers will vary. The goal is for students to make the association between velocity of molecules with temperature. The is an important step. Encourage students to give a thoughtful, thorough explanation.

7. What is the relationship between air temperature and force of gas molecules?
Answers will vary. The goal is for students to make the association between increased temperature with increased force. Pressure is force per unit area.

How did you form this conclusion?
Answers will vary. This is an important part. Encourage students to give a thoughtful, thorough explanation.

Answers will vary. The instructor may use this as a springboard to an extension to this lesson. The instructor may opt to explore questions as a class or to divide the class into small groups that will report their findings to the class. A good place to start is the
Beginner's Guide to Propulsion.

Related Pages:
Standards
Activity
Worksheet
Propulsion Activity Index
Propulsion Index

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