Accuracy of pH paper The use of pH paper is similar to the use of a Galileo thermometer. Particular colors indicate certain values, and each measurement is only accurate within a unit or two. While pH paper is great for quick qualitative work, it fails at highly accurate quantitative work.

Sodium hydroxide turns blue litmus red.

The litmus test is quick and simple, but it suffers from a few limitations. First, it’s not an accurate indicator of pH; it does not yield a numerical pH value. Instead, it roughly indicates whether a sample is an acid or a base. Second, the paper can change colors for other reasons besides an acid-base reaction.

At very high or low pH values, pH paper may not give an accurate reading. If the pH is below 0, for example, your pH paper would not give you an accurate reading, since pH strips are not designed for extreme pH values.

Acids and bases are important in living things because most enzymes can do their job only at a certain level of acidity. Cells secrete acids and bases to maintain the proper pH for enzymes to work. The enzyme pepsin, which helps break down proteins in the stomach can only function optimally in the low pH environment.

pH change as the cause of tooth decay When we eat food containing sugar, then the bacteria present in our mouth break down the sugar to form acids. This acid lowers the pH in the mouth. Tooth decay starts when the pH of acid formed in the mouth falls below 5.5. This sets in tooth decay.

When the pH in the mouth falls below 5.5, tooth decay starts. Bacteria present in the mouth produce acid by degradation of sugar and food particles which remain in the mouth after eating. The acid produced in the mouth attack the enamel thereby, creating tooth decay.