How can litmus paper and phenolphthalein be used to tell whether a solution is an acid or a base? Be specific.

Both litmus paper and phenolphthalein are used as acid/base (pH) indicators.

Litmus paper:

Litmus paper will turn either blue or red when a drop of solution is added to the paper. Red indicates an acidic solution (pH is 8.3).

Phenolphthalein:

Phenolphthalein is commonly used during acid/base titrations. When the solution is acidic and the indicator is added, it will remain colorless. If the solution is basic, the phenolphthalein will turn pink.