How to distinguish between "a" and "ang" in Pinyin?

1.”a“is a simple final. try to say ”a“ open your mouth wide and relax your jaw。put your tongue in its lowest place. your nasal packing the air flow comes out of your mouth.
2."ang" is the nasal finals。What is nasal? It means the sound comes from the nose instead of from the mouth.
first put your tongue in its lowest place and your nasal passage, so all comes out of your mouth, then make your soft palette down to open the nasal path and gradually raise the rear of your tongue to touch against the soft palate, so "ang" comes out of your nose