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# Combined Gas Law

## Calculations involving temperature, volume, and pressure for different gases

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Balloon on the Moon

### Balloon on the Moon

Credit: Warren Denning
Source: https://commons.wikimedia.org/wiki/File:Congrats_bqt.jpg

Whether it’s a graduation, a promotion, or perhaps retirement, the giving of balloons has become a tradition for many. Brightly colored and helium-filled, the balloons convey a festive note to the occasion, indicating celebration and accomplishment.

#### Amazing But True

• The first humans to set foot on the moon landed there on July 20, 1969. It was a momentous event that was watched on television around the world. The celebration by the astronauts was put off until they safely returned to Earth. But what if they had held a party on the moon? How would those balloons have held up?
• The pressure inside Apollo 11 had to be enough that the astronauts could survive. So the balloons would have been inflated to fill up before they stepped out of the space craft. The lunar atmosphere is almost non-existent, so there would have been a significant pressure drop on the outside. The combined gas law would predict that the balloon would have expanded rapidly since the pressure decreased.
• Credit: NASA
Source: http://en.wikipedia.org/wiki/File:Aldrin_with_experiment.jpg

The first men on the moon had much to celebrate for, but they were only on the surface for 34 minutes [Figure2]

• How hot or cold was it? The answer to this depends upon when they landed. The moon rotates on its axis about once every 27 days. In full exposure to the sun the surface temperature would be over 120°C (definitely hot enough to boil water). This temperature increase would also cause the balloon to expand, probably enough to burst. Better pick another time. At full darkness, the surface temperature is in the neighborhood of -153°C. Well, at least the balloon wouldn’t expand. The extreme cold would definitely cause a reduction in volume (and some decrease in pressure) due to the lower temperature.
• Watch a video of the first moon landing at the link below:

#### Show What You Know

1. When would be the best time for the astronauts to get out their balloons?
2. What gases have been observed in the lunar atmosphere?
3. Why does a hot air balloon rise?
4. Is there a limit to how high a hot air balloon can rise?

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