what is boilng point?

Question

what is boilmg ponit.what are the factors effecting boiling point

Answer 1

The boiling point of a substance is the maximum temperature at which a liquid can remain a liquid. Adding a small amount of heat energy (latent heat of vaporization) can convert the liquid into a gas. A pure liquid may change to a gas at temperatures below the boiling point through the process of evaporation. Any change of state from a liquid to a gas at boiling point is considered vaporization. However, evaporation is a surface phenomenon, in which only molecules located near the gas/liquid surface could evaporate. Boiling on the other hand is a bulk process, so at the boiling point molecules anywhere in the liquid may be vaporized, resulting in the formation of vapor bubbles.

A somewhat clearer (and perhaps more useful) definition of boiling point is "the temperature at which the vapor pressure of the liquid equals the atmospheric pressure."

Saturation temperature and pressure
A saturated liquid contains as much thermal energy as it can without boiling (or conversely a saturated vapor contains as little thermal energy as it can without condensing).

Saturation temperature means boiling point. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase. The liquid can be said to be saturated with thermal energy. Any addition of thermal energy results in a phase change.

If the pressure in a system remains constant (isobaric), a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy (heat) is removed. Similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied.

The boiling point corresponds to the temperature at which the vapor pressure of the substance equals the ambient pressure. Thus the boiling point is dependent on the pressure. Usually, boiling points are published with respect to standard pressure (101.325 kilopascals or 1 atm). At higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased ambient pressure up to the critical point, where the gas and liquid properties become identical. The boiling point cannot be increased beyond the critical point. Like wise, the boiling point decreases with decreasing ambient pressure until the triple point is reached. The boiling point cannot be reduced below the triple point.

If the Heat of Vaporization and the vapor pressure of a substance at a certain temperature is known, the normal boiling point (under standard pressure) can be calculated by:

Where TB is the boiling point under standard pressure, R is the ideal gas constant, P0 is the vapor pressure at a given temperature, T0 is that temperature, and ΔHvap is the heat of vaporization of the substance.

Saturation Pressure, or vapor point, is the pressure for a corresponding saturation temperature at which a liquid boils into its vapor phase. Saturation pressure and saturation temperature have a direct relationship: as saturation pressure is increased so is saturation temperature.

If the temperature in a system remains constant (an isothermal system), vapor at saturation pressure and temperature will begin to condense into its liquid phase as the system pressure is increased. Similarly, a liquid at saturation pressure and temperature will tend to flash into its vapor phase as system pressure is decreased.


[edit] Intermolecular interactions
In terms of intermolecular interactions, the boiling point represents the point at which the liquid molecules possess enough thermal energy to overcome the various intermolecular attractions binding the molecules into the liquid (eg. dipole-dipole attraction, instantaneous-dipole induced-dipole attractions, and hydrogen bonds). Therefore the boiling point is also an indicator of the strength of these attractive forces.

The boiling point of water is 100 °C (212 °F) at standard pressure. On top of Mount Everest the pressure is about 260 mbar (26 kPa) so the boiling point of water is 69 °C. (156.2 °F).

For purists with a knowledge of thermodynamics, the normal boiling point of water is 99.97 degrees Celsius (at a pressure of 1 atm, i.e. 101.325 kPa). Until 1982 this was also the standard boiling point of water, but the IUPAC now recommends a standard pressure of 1 bar (100 kPa). At this slightly reduced pressure, the standard boiling point of water is 99.61 degrees Celsius.

Answer 2

It seems to me you are asking me to answer a homework question.

The boiling point is the temperature at which a liquid's vapor pressure equals the atmospheric pressure. At that temperature, the liquid converts from liquid to gasseous state.

A liquid exhibits some vapor pressure. At constant pressure the vapor pressure increases with increased temperature.

Therefore temperature is a major influence upon boiling point.

Note that if you reduce the atmospheric pressure, the temperature where the vapor pressure equals the now reduced atmospheric pressure is lower than the temperature where vapor pressure equaled the original atmospheric pressure. An interesting application where pressure is reduced to achieve boiling at a lower temperature is in oil refining. Heavier organic fractions would decompose before boiling under standard atmospheric conditions. By reducing the pressure (vacuum distilling), the boiling happened at lower temperature and decomposition did not happen.

Similarly if you increase atmospheric pressure, the temperatre where the vapor pressure equials the now increased atmospheric pressure is higher than the temperature where the vapor pressure equaled the original atmospheric pressure. An interesting application of this is the automotive cooling system. The system is equipped with a pressure cap and as the coolant warms, pressure rises preventing the coolant from boiling even though the temperature is above the normal water boiling point.

Answer 3

Boiling point is when the vapor pressure of a liquid equals the atmospheric pressure.
Things that effect boiling point are impurities and atmospheric pressure (this is why cakes have different directions for cooking at a high altitude; the atmospheric pressure is lower so the boiling point is lower)

Answer 4

Boiling point is the temperature at which a liquid changes to gas. The boiling point is a function of pressure i.e. the boiling point increases with increase in confining pressure.

Boiling point is also the temperature beyond which the liquid can not be heated. Additional heating beyond attaining the boiling temperature will not increase the temperature of the liquid but will increase the rate of evaporation.

Answer 5

The boiling point of a substance is the maximum temperature at which a liquid can remain a liquid. Adding a small amount of heat energy (latent heat of vaporization) can convert the liquid into a gas. A pure liquid may change to a gas at temperatures below the boiling point through the process of evaporation.
The things that affect boiling are ofcourse heat, temp, air pressure, impurity! etc.....
luv,
me

Answer 6

When molecular size is increased or just generally bigger it means that there will not be as many electrons/molecules in a particle. The molecules are more likely to hit off each other creating tension and heat. Boiling points are generally averaged out with the rate of heat produced. Because molecules are both positive and negative, this changes the speed and the reaction of the molecules that hit eachother in a distinctive particle.

Answer 7

boiling point is the temperature required for a given substance to reach the point of turning from a liquid to a gas.
i.e. a pot of water begins to boil and lets off steam.

the boiling point of any given substance are effected by altitude

Answer 8

boiling point is the point at which a liquid turns into gas. factors that affect boiling point are temperature, pressure, impurities, and how much of the gas is in the air already.

Answer 9

boiling point is when like water boils at 100 degree and it turns to boiling water

Answer 10

point at which water disappears...is boiling point.
Its actually 100 degree celcius in case of water.
Different chemicals have different boiling point.