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Gas Density

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Giants in the sky

Gas Density- Blimps and Hot Air Balloons

Recall that density equals mass over volume. Gasses that are less dense than others are able to to “float” above them because they are lighter.

Credit: user: focus_mankind
Source: http://commons.wikimedia.org/wiki/File:Luftschiff_small.jpg
License: CC BY-NC 3.0

Could it be magic? [Figure1]


Have you ever gazed up in the sky and seen giant blimps or hot air balloons drifting easily aloft the clouds? How are these massive objects able to ascend into the sky? The answer is found in gas density. These two types of flying machines harness different techniques involving gas density to allow them to fly. Let’s have a look.

You’ve filled up balloons up before. What’s that gas that you fill up balloons with and turns your voice high pitched when you inhale it? That’s right, it’s Helium. Modern airships are essentially just giant party balloons that are able to hold passengers. Airships such as blimps or zeppelins have giant compartments in which Helium gas is stored in canisters. Helium gas, being less dense than air, allows for these enormous airships to roam the sky.

Instead of using helium to stay afloat, hot air balloons burn propane gas to heat up air under a large envelope or balloon. Because hot air is less dense than colder air, the balloon is allowed to float into the sky.

Creative Applications

1. Why is hot air less dense than cold air? (Hint: What gas law could this relate to?)

2. What other gases could also work in place of Helium in airships?

3. Research how pilots descend these forms of aircraft.

Image Attributions

  1. [1]^ Credit: user: focus_mankind; Source: http://commons.wikimedia.org/wiki/File:Luftschiff_small.jpg; License: CC BY-NC 3.0

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