Is water 'supposed' to boil at a lower temperature?

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    Boil Temperature Water
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Discussion Overview

The discussion centers around the properties of water, specifically its boiling point and the implications of hydrogen bonding on its state at various temperatures and pressures. Participants explore theoretical models, inter-molecular forces, and the conditions under which water can exist as a gas.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant recalls a biology teacher suggesting that water should exist as a gas at -90 degrees Celsius at 1 bar, prompting questions about the underlying reasons.
  • Another participant proposes that the teacher's statement might relate to the absence of hydrogen bonding in models of water, which would imply weaker inter-molecular forces.
  • A follow-up question asks whether a single atom of water can evaporate at temperatures lower than 100 degrees Celsius.
  • It is noted that a single molecule of water cannot exist in liquid or solid states.
  • One participant explains that water can evaporate below 100 degrees Celsius if its partial pressure in the gas phase is less than 1 atm, citing practical observation with a bowl of water.
  • Another participant confirms that water remains liquid at 1 atm between 0 degrees Celsius and 100 degrees Celsius due to hydrogen bonding, questioning the attraction between hydrogen and oxygen atoms in water molecules.
  • It is clarified that boiling occurs when vapor pressure equals atmospheric pressure, while evaporation can happen at any temperature from the surface of the liquid.

Areas of Agreement / Disagreement

Participants express various viewpoints on the implications of hydrogen bonding and the conditions for water's state, indicating that multiple competing views remain and the discussion is not resolved.

Contextual Notes

Some assumptions about inter-molecular forces and the conditions for evaporation and boiling are not fully explored, and the discussion relies on different models of water's behavior under varying pressures and temperatures.

TheAbsoluTurk
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A biology teacher once said to his class something to the effect of water posessing qualities that it should not. I don't remember what reasons he gave but my notes say that water 'should' exist as a gas at -90 degrees Celsius at 1 bar.

Do any of you know why this is?
 
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I assume what he meant was that if you model water without taking into hydrogen bonding it has much weaker inter-molecular forces?
 
Jorriss said:
I assume what he meant was that if you model water without taking into hydrogen bonding it has much weaker inter-molecular forces?

Does that mean a single atom of water evaporates at a lower temperature than 100 degrees Celsius?
 
a single molecule of water can't form liquid or solid
 
Water can evaporate at temperatures below 100C if its partial pressure in the gas phase in less than 1 atm. Just set out a small bowl of water in your kitchen for a few days and see what happens. Water will always evaporate if its partial pressure in the gas phase is less than the equilibrium vapor pressure at the liquid temperature.

Chet
 
Ok, from what I've read from you guys, water exists as a liquid at a pressure of 1 atm at temperatures of 0 degrees Celsius and 100 degrees Celsius because of hydrogen bonding. That means the individual hydrogen atoms in each H20 are attracted to the oxygen atom of other water molecules, right?
 
What he means is that, if you compare water to other molecules of a similar size (ammonia, hydrogen chloride, methane) it has unusually high melting, boiling points and specific heat capacities due to the hydrogen bonding in water.
 
Boiling occurs when the vapour pressure equals the atmospheric pressure. Vapour then forms throughout the body of the liquid. Evaporation occurs from the surface of the liquid at all temperatures.
 

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