Water vapor / energy question

In summary, the conversation discusses a system consisting of a shallow pan and a smaller beaker filled with distilled water, enclosed by a bell jar and starting at room temperature. The question is whether the beaker loses water to evaporation while the pan gains it, given that the water at the top of the beaker has a higher potential energy. However, considering the thermal energy and gravitational potential energy of water, it is concluded that there is no tendency for water to preferentially evaporate from the column.
  • #1
Mike_In_Plano
702
35
The following is something that puzzles me a bit, and I'd appreciate some insight in the matter.
Thank You :)

Given the following:
A shallow pan with a smaller diameter beaker sitting in it's center
Both the pan and the beaker contain distilled water
The level of the water in the beaker is substantially high than that in the pan
The pan and beaker are additionally enclosed by a bell jar (with an id = to the od of the pan)
The bell jar is evacuated until only water vapor remains
The system starts at a uniform temperature, say room temperature
The system ends at the same temperature via thermal conductivity of a plate that the pan sets on.

Here's my question:
Does the beaker loose water to evaporation while the pan gains the water? After all, the water at the top of the beaker is at a higher potential energy than that at the top of the pan.

Thanks for your considerations,

Mike
 
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  • #2
Maybe it would help to consider the following:

Thermal energy (kT) at room temperature is 4 * 10^-21 J.
Gravitational potential energy (mgh) for water atoms at the top of a 1-meter high column is 3*10^-25 J.
Energy of vaporization for a water molecule: 7 *10^-20 J.

The amount of potential energy is negligible in comparison to thermal energy, so there is no tendency for water to preferentially evaporate from the column.
 

Related to Water vapor / energy question

1. What is water vapor and how does it affect the Earth's atmosphere?

Water vapor is the gaseous form of water in the Earth's atmosphere. It is a key component of the Earth's water cycle and plays a crucial role in regulating the planet's temperature through the greenhouse effect. Water vapor absorbs and emits heat, trapping it in the atmosphere and keeping the Earth warm enough to sustain life.

2. How is water vapor formed in the atmosphere?

Water vapor is formed through the process of evaporation, where liquid water is converted into a gas by absorbing energy from the sun. This process occurs primarily at the Earth's surface, such as bodies of water or moist soil, and is also aided by transpiration from plants.

3. What is the relationship between water vapor and weather?

Water vapor is a key factor in the formation of weather patterns. When warm air rises and cools, it condenses into clouds, and if the conditions are right, precipitation occurs. Water vapor also helps to regulate temperature, as it can absorb and release heat depending on the amount present in the atmosphere.

4. How does water vapor contribute to the greenhouse effect?

Water vapor is the most abundant greenhouse gas in the Earth's atmosphere, making up about 60% of the total. It traps heat in the atmosphere, preventing it from escaping into space, and helps to regulate the Earth's temperature. However, too much water vapor in the atmosphere can lead to an increase in the greenhouse effect and contribute to global warming.

5. Can the amount of water vapor in the atmosphere change over time?

Yes, the amount of water vapor in the atmosphere can vary due to natural and human-induced factors. Changes in temperature, humidity, and wind patterns can all affect the amount of water vapor present. Human activities, such as burning fossil fuels and deforestation, can also contribute to changes in the amount of water vapor in the atmosphere through the production of greenhouse gases.

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