This is question regarding sublimation.

 

When we heat sublimants like ammonium chloride , Iodine etc it truns to vapor stage directly. Do they beomce vopour directly or the interphase ( liquid) is not noticable? What happens in the reverse ie when we condense vapors?

From Wikipedia (http://en.wikipedia.org/wiki/Sublimation_%28chemistry%29):

 

Sublimation of an element or compound is the change from a solid directly to a gas with no intermediate liquid stage

 

The same happens during deposition (condensation is from gas to liquid, not solid). This does not mean that there doesn't exist a liquid phase for those compounds. Depending on temperature and pressure, there are a wide variety of chemicals that exhibit sublimation if the pressure of the environment changes.

 

To understand more about this check out wikipedia's "phase diagram" page.

Thanks