Which tool is appropriate for testing whether liquids are acids or bases?

Litmus paper is a practical and widely used tool for testing whether liquids are acidic or basic. It works by changing color in response to the pH level of the liquid being tested. When a drop of a liquid is placed on blue litmus paper, it will turn red if the liquid is acidic (pH less than 7) and remain blue if it is basic (pH greater than 7). In contrast, red litmus paper turns blue for basic liquids.

The effectiveness of litmus paper lies in its simplicity and immediate visual indicator, making it an accessible choice for determining the acidity or basicity of a solution without the need for more complex equipment. This makes it suitable for classroom experiments or quick tests in various settings.

While a pH meter can also be used to measure acidity and basicity more precisely, it is a more complex tool that requires proper calibration and understanding of the principles of operation. A thermometer is solely used to measure temperature and does not provide information about the chemical nature of a liquid. A refractometer is used for measuring the refractive index of liquids, which relates to concentration but does not directly indicate whether a liquid is an acid or a base.