why摩擦生熱?水在太空一遇熱即change gas?

1) When contacting surfaces move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy, or heat. Contrary to earlier explanations, kinetic friction is now understood not to be caused not by surface roughness but by chemical bonding between the surfaces.
from Wiki.

2) 因為真空氣壓比正常地球表面氣壓低, 水既沸點會下降, 導致水係低過一百度已變為氣態

1) Atoms break away during sliding, energy used to break chemical bonds.
from http://www.phys.ufl.edu/courses/ ... 6_friction_lec1.pdf

2) 水既沸點會隨氣壓改變, 只要氣壓令其沸點降至低於水既溫度, 水就會變成氣態
<i>請參考 http://hk.youtube.com/watch?v=9q5gEZGoBnk&feature=related<i>