Question

1. All the food was gone.
2. All the food were gone.
3. All the foods was gone.
4. All the foods were gone.

(Which ones are grammatical? What kind of noun is 'food'? A countable noun or an uncountable noun? A material noun or a collective noun? Thank you.)

Answer 1

Only #1 is correct.

The word "food" is a non-count noun:
http://grammar.ccc.commnet.edu/grammar/noncount.htm