Hi I'm in Chemistry too this year,
I believe D is correct because usually physical changes are things like density, color or quantity.
Answer:
Sodium reacts with the oxygen in air. It reacts vigorously with oxygen and the moisture that is already present in the air and thus catches fire.
I think B but i'm not for sure
Answer:
The answer I believe is B. Erosion
Explanation:
Just sounds better than all the other choices.
P=18000000/6 zeros. not sure how to do rest