This was an exam question. Can u please write detailed and scientific reasons for this answers.
2007-03-29 05:14:50 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
For one, water can change state between solid and liquid at 0 C, far below the boiling point of 100 C ;)
Okay, seriously though, the reason is simpe: the boiling point of 100 C is just that temperature at which the equilibrium water vapor pressure is 1 atmosphere. So below the boiling point, you still have significant vapor pressure, it's just that it isn't 1 atmosphere.
Why you get vapor pressure is simple: in any collection of liquid state or gaseous state matter, you will find a range of kinetic energies associated with the molecules...some will have a lot of kinetic energy, a lot wil havea moderate amount of kinetic energy, and some will have a realitvely small amount of kinetic energy (the distribution of kinetic energy follows a Boltzmann distribution, if you care to know). So, there are always some liquid molecules with sufficient kinetic energy to overcome intermolecular forces and escape as vapor. Conversely, there are also some gas state molecules that don't have sufficient kinetic energy to overcome intermolecular forces, and they will condense out. What you thus get is a dynamic equilibrium. The bottom line is that for all temperatures above absolute zero, there will ALWAYS be some vapor pressure, though such vapor pressure falls off exponentially with (absolute) temperature.
2007-03-29 05:31:07 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The atmospheric pressure will affect the boiling point.
In Denver (the mile high city) water boils at 95 C because the pressure is only 83% of that at sea level.
At higher pressures the water will boil at temperatures higher than 100 C.
2007-03-29 05:29:29 · answer #2 · answered by Thomas C 6 · 0⤊ 0⤋
I think The intramolecular space between the atoms increases as the temperature increases in water so if u raise the temperature of water so near 100 ,the kinectic molecular energy or surface of water increases and space between atoms of water tends to increase and the atoms leaving the surface of water that change into other state of matter i.e. GAS
2007-03-29 05:24:12 · answer #3 · answered by Don 3 · 0⤊ 0⤋
the term 'boiling point' implies behavior at 1 atmosphere of pressure. (actually 99.97 C at 1 atmosphere of pressure, 101.325 KPa). If the pressure is dropped below that, the boiling temperature drops. For example, "On top of Mount Everest the pressure is about 260 mbar (26 kPa) so the boiling point of water is 69 °C."
2007-03-29 05:25:41 · answer #4 · answered by Tim J 1 · 0⤊ 0⤋
All substances have a vapour pressure.
Water will evaporate at all temperatures above 0°C.
The evaporation rate is much slower at lower temperatures and, if it's in a windy position, the evaporation rate will increase ... the breezier the better. (Haven't you seen a puddle of rain dry up on a cold day ?)
Even ice exerts a vapour pressure and, with a wind, the ice will sublimate.. (change directly to vapour).
2007-03-29 08:50:02 · answer #5 · answered by Norrie 7 · 0⤊ 0⤋
Water changes its state at temperatures well below 100C when there are impurities mixed with it.
2007-03-29 05:20:53 · answer #6 · answered by milinda 1 · 0⤊ 0⤋
when water is heated then the molecular force between the atoms weakens due to which it is converted to gas as gas have weak molecular force between their atoms
2007-03-29 05:38:01 · answer #7 · answered by Sam 2 · 0⤊ 0⤋
coz of excess pressure
2007-03-29 05:24:31 · answer #8 · answered by Anonymous · 0⤊ 0⤋