Explain what happens when boric acid is heated.

On heating orthoboric acid $(H_{3}BO_{3})$ at $370 \ K$ or above,it loses a water molecule to form metaboric acid $(HBO_{2})$.
On further heating,metaboric acid loses more water to yield boric oxide $(B_{2}O_{3})$.
The reactions are as follows:
$H_{3}BO_{3} \xrightarrow{370 \ K} HBO_{2} + H_{2}O$
$2HBO_{2} \xrightarrow{\Delta} B_{2}O_{3} + H_{2}O$