# What conditions are necessary to fling water in the air such that it all turns to vapor?

**URL:** <https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540>\
**Category:** Factual Questions\
**Created:** [September 18, 2018, 4:56pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540 "2018-09-18T16:56:15Z")\
**Posts on this page:** 5\
**Page:** 2

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [September 19, 2018, 3:41pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540/21 "2018-09-19T15:41:35Z")

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> [@Pleonast](#):
>
> I accept your nitpick, because “directly” is subjective. But it’s like saying a chainsaw cannot directly fell a tree–all it does is remove the tree’s support and then relies on local gravitation to pull it down.

I think it’s a meaningful nitpick because of the existence of another type of humidifier which _does_ directly turn its liquid water into vapor - by boiling it.

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**Author:** ![Skammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skammer/32/143_2.png) [@Skammer](https://boards.straightdope.com/u/Skammer)\
**Post date:** [September 19, 2018, 4:41pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540/22 "2018-09-19T16:41:27Z")

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Y’all, don’t bother inviting me to any of your picnics.

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**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\
**Post date:** [September 19, 2018, 7:57pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540/23 "2018-09-19T19:57:05Z")

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So I ran some calculations out of curiosity and wanted to share the results.

Assumptions/Simplifications : Assumed 1/2 lb (a cup) of water is thrown. Assumed the thrown water disperses into a 2 ft diameter cylinder that is in total 20 ft long (The water follows projectile motion path of total length of 20 ft). Assumed there is great heat transfer and all the energy for vaporization comes from this air tube 20 ft long, 2 ft in diameter.

Also assumed that the air is bone dry initially and all this takes place at sea level 14.7 psia.

With those assumptions:  
Temperature of air needed to have all the water vaporize is about 1700 F, when water in the cup is at 210 F.

At these conditions, the amount of air in the cylinder is about 2.4 lb and the final temperature of air in the cylinder is 169 F.

Hope the above gives some perspective.

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**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\
**Post date:** [September 19, 2018, 8:13pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540/24 "2018-09-19T20:13:34Z")

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> [@am77494](#):
>
> With those assumptions:  
> Temperature of air needed to have all the water vaporize is about 1700 F, when water in the cup is at 210 F.

Wow! What a fascinating and unexpected result! I would have never guessed. That means maybe the only place you could do this is on an active volcano after all! With lava around that temperature, the air above might be sufficiently hot to vaporize the water before landing on the flowing lava. I’ll have to give this a try the next time there’s an eruption and report back with my results. I hope my Solo cup doesn’t melt too soon.

Thanks so much for figuring that out.

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**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\
**Post date:** [September 19, 2018, 8:20pm UTC](https://boards.straightdope.com/t/what-conditions-are-necessary-to-fling-water-in-the-air-such-that-it-all-turns-to-vapor/821540/25 "2018-09-19T20:20:41Z")

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Or, you could be standing directly in front of a jet engine.

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