In a sentence, the subject is an uncountable noun and the verb be is used______

In a sentence, the subject is an uncountable noun and the verb be is used______

is /was

When the subject is an uncountable noun, the predicate verb should use

When the subject is an uncountable noun, the predicate verb should use is

What is the verb be before uncountable nouns?
Why?

Fixed collocation: uncountable be, is, was, many, a little; little
Can't count, how to know how many, still use are?

What does the uncountable noun be verb use?

It's all singular, but it depends on the tense to decide whether to use is or was