Draw the pH scale or provide a diagram for students. The pH of a solution ranges from 0 to 14. Solutions with a pH from 0 to 6 are acidic while solutions with a pH from 8 to 14 are considered basic or alkaline. A pH of 7 is neutral.
Provide pH testing devices to students. Inexpensive litmus paper changes color in the presence of acids or bases. The pH indicator strips change color and are compared to a chart to determine the pH of the solution. More expensive pH meters and sensors give precise pH readings. Specialized pH testing kits for water and soil often use dye indicators to determine pH.
List and describe the safety precautions for students. When testing common household materials such as orange juice or soda, remind students to clean up spills immediately and wash their hands. If they get materials in their eyes or on clothing, flush with water. No eating or drinking is allowed during the lab. If the pH testing involves strong acids or bases such as bleach, provide aprons and glasses for each student and information about safely handling solutions.
Provide plastic or paper cups to hold the solutions for testing. Common solutions include acids such as lemon juice (pH 2), vinegar (pH 3), cola (pH 3 to 4.5) and coffee (pH 5). Distilled water has a neutral pH. Basic or alkaline solutions include egg whites (pH 8), baking soda dissolved in water (pH 8 to 9) and detergents (pH 10 to 11).
Record the test results. The pH scale is a logarithmic scale, and there is a ten-fold difference between each value. For example, a solution with a pH of 5 is 10 times more acidic than a solution with a pH of 6. Students may record the pH values on a chart and discuss types of acidic and basic solutions.