Final answer:
Neutrality, acidity, and alkalinity are determined by the pH scale, with 7 being neutral, values below 7 acidic, and above 7 alkaline. Universal indicator paper changes color in response to the pH level of a solution, providing a visual indication of its acidity or alkalinity.
Step-by-step explanation:
The concept of neutrality, relative acidity, and alkalinity can be described using the pH scale, which is a numerical range that indicates how acidic or basic a substance is. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, pH values less than 7 indicate acidity, and pH values greater than 7 indicate alkalinity. To measure pH, universal indicator paper can be employed. This paper contains a mixture of indicators that exhibit a variety of colors when dipped into solutions with different pH values.
For example, in the presence of an acid, the universal indicator paper might display a red to orange color, corresponding to pH values between 1 (strongly acidic) and 6. Conversely, if the solution is basic, the paper changes to colors like blue to purple, indicating pH levels between 8 and 14. A neutral solution would result in a green color on the pH paper. By comparing the color change on the universal indicator paper to a color scale provided with the paper, one can determine the approximate pH of the solution.