How does water rise to form clouds if oxygen is heavier than nitrogen?

In summary: Water molecules rise together with warm air. The air warmed up near to the ground will rise up as the molecules have greater speeds as those of cold air. The warm molecules above a hot stop exchange momentum and energy with he cold molecules above, and that results a net upward velocity of the air column. At great height, where the temperature is low, the vapour condenses and clouds form.
  • #1
channel1
73
0
1 - how does water rise to form clouds if oxygen is heavier than nitrogen?

when it turns into a gas its hydrogen and oxygen---why does it rise (to form clouds) if oxygen is heavier than nitrogen, which makes up 78% of the Earth's atmosphere?

*please note that I'm not confused as to the radiative excitation of the molecules that allow them to break the surface that starts the evaporation process

2 - is the evaporating gas always radiatively ionized or just sometimes?
 
Physics news on Phys.org
  • #2


The water molecules rise together with warm air.
The air warmed up near to the ground will rise up as the molecules have greater speeds as those of cold air. The warm molecules above a hot stop exchange momentum and energy with he cold molecules above, and that results a net upward velocity of the air column. At great height, where the temperature is low, the vapour condenses and clouds form.

The molecules of a gas have so high speeds that the effect of gravity during collisions can be totally neglected. The molecules change direction in the collision, and the distribution of their velocities stays random. They do not settle down.

By the way, oxygen molecules and nitrogen molecules make up the atmosphere, and water vapour is from H2O molecules (relative molar mass 18 ) , lighter either than O2 (32) or N2 =28) .

Evaporation means that a molecule has so big KE that its energy is enough to overcome the attractive potential inside the fluid. It does not need excitation. Simply, as the velocity distribution is random, there is some probability that a molecule has high enough speed to leave the surface of the liquid.

ehild
 
  • #3


This is a homework problem? So I won't just tell you the answer...

Some concepts to help you wrap your head around this:
1. What we usually think of as "water" is a mix of H+, OH- and H2O.

2. Gas phase of water is "steam" ... it is H2O gas - it can go places because it has a lot of kinetic energy.

3. Water in clouds is vapor - liquid water droplets. They condense on dust - which is composed of (small) solid lumps.

4. a gas does not have to be "lighter than air" to rise, it just has to be less dense as a body. A balloon full of people is much heavier than nitrogen - yet it manages.

5. the atmosphere has a lot going on in it - i.e. it has weather - also eg. you will have noticed other heavy things getting carried up high ... like eagles and kites.

So ... considering all this, how does water get into the sky to make clouds?
 
  • #4


Simon Bridge said:
1. What we usually think of as "water" is a mix of H+, ...
A little out of date, I think. From http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/The_hydronium_Ion: [Broken]
hydrogen ions do not exist in aqueous solutions, but take the form the hydronium ion, H3O+
 
Last edited by a moderator:
  • #5


@haruspex: erk - OK, that's not just being pedantic, thanks. Replace H+ with H2O-H+ or something in the list. I did know about it, just didn't realize it's importance. This is why it is important for scientists to talk to each other aye.

Someone really pedantic could also point out the dissolved gasses and salts and so on and on in even very pure water. Just to head that one off: I wasn't making an exhaustive list ;)
 

1. How can water rise to form clouds if oxygen is heavier than nitrogen?

While oxygen is indeed heavier than nitrogen, it is not the only factor that affects the movement of air. The main mechanism behind the formation of clouds is convection, which is the transfer of heat through the movement of air. As the sun heats the Earth's surface, the air near the surface becomes warmer and less dense. This warm air rises, carrying water vapor with it. As it rises, it cools and condenses, forming clouds. Therefore, the weight of oxygen does not play a significant role in the formation of clouds.

2. Can water vapor rise without the help of oxygen?

Yes, water vapor can rise without the help of oxygen. As mentioned before, the main mechanism behind cloud formation is convection, which is driven by heat. Even in environments with little to no oxygen, such as high altitudes or outer space, water vapor can still rise and form clouds through convection.

3. If oxygen is heavier than nitrogen, why does water vapor rise instead of sinking?

While oxygen may be heavier than nitrogen, it is still much lighter than liquid water. In fact, water vapor is approximately 1000 times less dense than liquid water. This means that even though oxygen is heavier than nitrogen, it is still much less dense than water vapor and therefore can be carried upwards by convection.

4. How does water vapor turn into liquid water in the clouds?

As warm air containing water vapor rises, it eventually reaches a point where it cools enough for the water vapor to condense into liquid water droplets. This is because cooler air has a lower capacity to hold water vapor compared to warm air. These droplets then continue to grow and collide with other droplets, eventually forming visible clouds.

5. Can oxygen and nitrogen affect the formation of clouds in any way?

Oxygen and nitrogen do not directly affect the formation of clouds. However, they do play a role in the Earth's atmosphere and the overall weather patterns. The movement and distribution of these gases in the atmosphere can impact the temperature and pressure, which can indirectly affect the formation of clouds. For example, a high concentration of oxygen in a certain area may lead to more convection and therefore, more clouds in that area.

Similar threads

  • Sci-Fi Writing and World Building
Replies
4
Views
878
  • Biology and Chemistry Homework Help
Replies
1
Views
545
  • Introductory Physics Homework Help
Replies
14
Views
2K
Replies
1
Views
92
  • Introductory Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
14
Views
2K
  • Sci-Fi Writing and World Building
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
Replies
16
Views
2K
Replies
32
Views
1K
Back
Top