boiling point in vacuum

1.How can we calculate the b.p. of a substance(say,water) in vacuum?Any equations?

2.In the space,there are no air particles so there is no air pressure.Thus the

b.p. of a substance is extremely low.However,at the same time,the

space is very cold.Does water vaporize or freeze in the space?

更新:

But there is no air pressure in the outer space,which means the boiling point of water is very low.There seems to be a contradiction?

2 個解答

評分
  • 天同
    Lv 7
    8 年前
    最愛解答

    1. There is no simple equation to do this. But you could make reference to some fitted equations on the web. One such equation is given on the web-page below:

    http://www.ajdesigner.com/phpvaporpressure/water_v...

    This web-page also provide a calculator to find out the preesure required to reduce the water boiling point to a specified temperature.

    For more accurate data, you could refer to the table given in the web-page below:

    http://www.engineeringtoolbox.com/boiling-point-wa...

    2. It is best to refer to the phase-diagram of water (i.e. a diagram giving the variation of pressure with temperature), as given in the web-page below:

    http://www.chemix-chemistry-software.com/school/ph...

    On the diagram, you could observe that, under very low pressure and temperature (the space environment), water exists as either solid (ice) or gas (water vapour). Liquid water could never exist.

    In a free state, water in space generally exists in gas form. Ice only exists when water molecules ahere to some objects, such as meteors or comets.

  • 8 年前

    你話太空好凍,咁當然所有水都係冰。

還有問題嗎?立即提問即可得到解答。