# Tag Info

## New answers tagged evaporation

1

based on casual observation, believes that coffee will cool faster than ordinary hot tap water Let's revisit the "casual observation" part. Are the initial conditions the same? Water from a kettle will usually be hotter than from a coffee machine. And we tend to do things to coffee that we don't do to water, like add 10% of another liquid (milk) at low ...

8

I mean, they are heavier than air. No. Water is $H_2O$ which has a molecular weight of 18. Nitrogen is $N_2$ which has a molecular weight of 28. Oxygen is $O_2$ which has a molecular weight of 32. Argon is $Ar$ which has an atom weight of 40. So a water molecule has a mass that is less than that of all the significant components of air. But ...

2

First, water molecules are NOT heavier than air molecules. Air is mostly N2 (molecular weight 28) and some O2 (molecular weight 32). H2O has a molecular weight of only 18. So all else being equal, you would expect water vapor in the air to rise on average. However, at the level of individual molecules, gravity is a miniscule effect and swamped by the ...

0

Brownian motion - the force exerted by the surrounding gas molecules is far greater than that exerted by gravity. If you were being hit constantly, from all directions, by objects about your own mass but travelling around 500 m/s gravity would not affect you all that much either.

1

In most systems that involve the evaporation of water, gravity plays an extremely minor role. We can, in most cases, ignore the effects of gravity. What makes water boil/evaporate is the thermodynamic concept derived from the first and second law of thermodynamics. You can read this article to find out the derivation from entropy to the Clapyeron equation. ...

1

All of the molecules in the air are constantly colliding and rebounding off each other, which keeps them from "falling down". If they were to fall down under gravity the pressure would increase, and there would be a net force upward. This is why the pressure high up in the atmosphere is lower than at sea level. While water doesn't BOIL at room temperature, ...

1

Due to evaporation a layer of air forms between the water droplet and the hot surface which causes the system to vibrate by letting air escape in bursts and produce sound. I suggest reading about the description of the sound that was recorded in the Leidenfrost experiment. Article: http://www.nature.com/srep/2012/121010/srep00720/full/srep00720.html Video: ...

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