Is Adding Vinegar to Yeast A Physical or a Chemical Change????

4 answers

It's a chemical change, I think.
I think?
It is difficult to apply 'physical' or 'chemical' change descriptions to biological systems.

Of the two choices I would agree with Ms. Sue in that a chemical change is the better description. I am not sure the pH you are starting from. The drop in pH may increase (at about pH 4) or slow the cells processes and can be described as a chemical change. If the acid is sufficiently concentrated there may be cell shrinkage, due to loss of water from the cell, which could be described as a physical change.
The answer to your question is, Chemical (: