That is well. 
( That ( ( is well ) . ) )
(ROOT (S (NP (DT That)) (VP (VBZ is) (ADVP (RB well))) (. .)))
That is unwell.
( That ( ( is unwell ) . ) )
(ROOT (S (NP (DT That)) (VP (VBZ is) (ADJP (JJ unwell))) (. .)))