VERBS

be, feel, look, seem
The chairs felt hard and uncomfortable
become, go
Don't leave the cake uncovered or the icing will go hard
stay

ADV

extremely, very
a bit, fairly, quite, rather

PHRASES

rock hard
The toffee was rock hard

VERBS

be, look, seem
become, get
Life got very hard
make sth
If you tell the children the answers, it only makes it harder for them to do the work on their own
find sth
I found the exam quite hard

ADV

extremely, really, very
a bit, fairly, pretty, quite, rather