Comparing pure water and salt water, salt water has a higher boling point, and therefore takes longer time to boil. This is caused by the solute (salt) in the salt water, higher level of energy is required to convert the solute component to gaseous state.
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Why does adding salt make the boiling temperature of water rise???
Salt (or other solutes, like sugar) can easily dissolve in liquid water. However, taking the solute out of the water and putting it in the gas phase (air) requires a lot of energy. At temperatures around the water boiling point, these solutes stay in the liquid.
Now the total pressure in the liquid and the air at the boundary are the same- otherwise one would push the other into a smaller space. Part of the pressure in the liquid comes from the solutes, not the water. So the pressure due to the water alone is reduced compared to that of pure water at the same temperature. The vapor pressure, that is, the pressure of water vapor that would stay in equilibrium with the liquid, is reduced by the same amount because of the solutes.
Water boils when the vapor pressure of the water gets to be as big as the pressure of the atmosphere. At that point, vapor bubbles in the water can grow. You have to heat the liquid with solutes up more to get the vapor pressure in it to equal the atmospheric pressure, so it has a higher boiling point.
A very similar argument explains why solutes also lower the freezing point. Since the solutes are almost completely excluded from the solid (like from the gas) they stabilize the liquid. A search of this site will turn up some answers about freezing salt water.
Mike W. (and Tom J.)
[...] Also checkout Salt and the boiling point of water. [...]
thx…
thanks i needed it
thats weird but cool
This has no info. super suckie.
yah, but does suger affect it?
Nice, nice and simple. thank you very much
What is the boiling point of a very concentrated brine, of 80% NaCl by weight?
Many Thanks!
Bill Hauserman
This doesn’t explain why the volicity of hot water is a crisis in North American Ice Waters.
Update to ‘@939l1= To find the freezing point of water and how it differentiates from when salt is added to it.+”
Its completely irrelivant.
Time
I think it is the hydrogen bonding with the NaCl. Does hydrogen bonding occurs with chlorine atoms? If it does, then hydrogen bonding occurs with the water molecules, and hence the boiling point of water will increase.
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