Why is "les pates" incorrect?
You missed the circumflex accent on the A : les pâtes + "pasta" is about a certain quantity of pasta = some pasta -> des pâtes.
"les pâtes" would be "the pasta"
why do we put pate in plural sometimes and sometimes not??
"pâte" is dough; "pâtes" is pasta.
Well the dictionary should make that clearer in the "pâte" translation, as pasta is a viable translation for it's excercises.