Answer: acid; acidic
Step-by-step explanation:
You have a glass of pure water and add acidic lemon juice to it. This means that you are adding ACID to it, and the solution will become ACIDIC.
Pure water has a pH value of 7
Lemon juice has a pH value less than 7 i.e acidic
Therefore, addition of lemon juice to pure water will drop the latter pH from 7 to form a final solution that is ACIDIC.