QUICK! Need an answer to a riddle?

[Mashishka]

A riddle that has been brought to my attention and i need and answer fast...
this is a 5 letter word that becomes a 3 letter word and in the midst of it becomes an 11 letter word...HELP!

 

[♫☺yaLSew07☺♫]

dunno

idk

i don't know it!

 

[♥Moochy Baybeh♥]

the 1st word is water
the 2nd word is gas
& the 3rd word is evaporation

 

[glenn123]

Water...evaporation...gas.

 

[MyNameIs...]

The WATER turns into a GAS, and the gas turns into vapor or the stage of EVAPORATION (water vapor).