Image: pH testing
Greg using red cabbage juice to demonstrate pH changes.
- Karen Player
- © Australian Museum
pH is a logarithmic scale from 0 to 14 measuring how the acidic or alkaline a substance is. A pH of 7 is neutral, less than 7 is acidic, and greater than 7 is alkaline.
Pure water is neutral, with a pH of 7.0. But when chemicals are mixed with water it affects the pH. For example vinegar and lemon juice are acidic substances, while laundry detergents and ammonia are basic.
There are many factors that effect pH in the environment including natural and man made causes. Changes in pH can affect how chemicals dissolve in the water and whether organisms are affected by them. High acidity and alkalinity can be deadly to fish and other aquatic organisms.