Regarding water's boiling point and evaporation of sea water?

Question

The boiling point of water is 100*C. Had it been so, the water evaporated from the sea water would also have had the temperature of 100*C during day time (as it continuously evaporates during day time). But I can very easily play and swim in sea water which is not posibble to do at a temperature of 100*C. Explain this phenomena.

Answer 1

OH YEA! A fine question. The answer is:

Water might boil at 100ºC at standard conditions, you got that right, but there are two things to consider:

a) The sun heats only the surface of the sea, so it's perfectly normal if the surface is hotter than the bottom. But that is NOT the answer you want, it's the next:

b) Vapour pressure. I'll translate you an excert of this fluids mechanics book (Mechanics of Fluids, Victor L. Streeter, Ninth Ed.):

"Liquids vaporize because the molecules scape from the liquid surface. The molecules of vapour exert a parcial pressure in the surface, known as vapour pressure."

So the heat creates pressure above the surface, so it's also about the pressure on the surface what causes the water to vaporize. It's a matter of the pressure above the surface to be equal to the vapour pressure.

Answer 2

When water boils in a pan, heat energy is being supplied to the bottom of the pan by a burner, etc. When the bulk of the water reaches 100*C any additional heat will cause steam bubbles to form and rise to the surface. When the action is pronounced it is called boiling.

Evaporation is very different and requires far less energy. When heat is added to a water surface (by the sun or by warm air, etc.) individual molecules of water (instead of the entire bulk) receive enough energy to break the bonds of surface tension and leave the liquid to float away as vapor. If the room is at 100% relative humidity, about as many water molecules will return to the pan of water as leave it and it will seem as though no evaporation has occurred. However, if the air is dry (say 50% relative humidity) twice as many water molecules will leave the pan as return to it. Even cold water will evaporate in dry air. Even ice will evaporate by sublimation without melting. The sea water is constantly evaporating even though it is comfortable enough for you to swim in.

Answer 3

Water has a vapor pressure at any temperature. At 100 C, that vapor pressure is one atmosphere, so boiling takes place. At 37 C, the vapor pressure is much less (0.063 atmospheres) but still greater than zero, so evaporation (as from your skin) can still take place.

Seawater does not boil at exactly 100 C. The dissolved salt raises the boiling point a fraction of a degree.

Answer 4

Yes, the boiling point of water is 100*c..But see for Eg.,u place a glass of water in hot summer and splash that glass of water on the floor,which will evaporate fastly!.Of course the second one.There U can see that there is an inversely proportionality b/n area of sample and the evaporation temp.Lager the area lesser the evaporation temp. Got it!.

Answer 5

Pretty simple. Water molecules move around at all sorts of speeds. The average speed of their movement is the water temperature. Some molecules move faster and tend to break up (evaporate), that doesn't mean the body of water they evaporate from is boiling. If it was, all the water molecules would leave.

Answer 6

Evaporation Of Seawater

Answer 7

you are mixing up evaporation with boiling
boiling occurs at a constant temperature at which the liquid is rapidly converted to its vapour state in the form of steam which has latent heat associated with it
evaporation occurs at all temperatures and the temperature of the water vapour produced during evaporation will be the same as the sea water at that time.

Answer 8

When water reaches its boiling point it is called vaporisation and the liquid transformed to gases. Again with the help of sun light the upper surface of sea water turns into gases is called evaporation.

Answer 9

Although the above answers are correct, the answers and your question leave out a very important item... That being: "will not reach 100 IN AN OPEN CONTAINER." Put the water in a pressure cooker and the boiling temperature will be higher than 100 no matter what the altitude might be.

Answer 10

Water evaporates no mater what the current temperature is- even when it is below freezing the water molecules will still evaporate