pH testing for schools: The pH scale

pH is a vital measurement in many different industries and applications. pH is used in a wide range of ways, with digital pH testers providing an accurate and easy way to check this important parameter. Read on to learn more about pH testing and the pH scale:

What is pH?

pH is a measurement of how acidic or alkaline a solution is. When testing pH, the range of the measurement is from 0 to 14 on a scale, where 0 is the most acidic, 14 is the most alkaline, and 7 is true neutral. The pH scale is logarithmic and increases tenfold with each number, which means that a solution with a pH of 5 is ten times more acidic than a solution with a pH of 6. 

What do you use to measure pH?

There are two common methods to measure pH:

Indicator paper changes colour when it is dipped into a solution, providing a more general idea of pH within a range. An indicator may also be added to a solution directly as a liquid.

pH meters or pH testers are a digital method of measuring pH, where an electrode reads the pH of the sample and provides an accurate, numeric value on a screen. These meters are available in a range of forms, from small pocket-sized testers and handheld meters to use out in the field to advanced laboratory equipment that is placed on a benchtop. 

Digital pH testing is used in many different industries and applications, including:

• Environmental monitoring to test the quality of water in lakes, rivers and ponds
• Food and beverage production to make products safe and consistent
• Gardening and farming to improve the growth and health of plants
• Swimming pool measurement to make sure the water is safe for use
• Pet care to check the condition of the water in fish tanks
• Laboratories to test the acidity or alkalinity of chemical solutions

The pH scale

The pH scale goes from 0 to 14 and provides information about how acidic or alkaline a solution is.

This is an example of the pH scale:

pH is not a set value, and will vary depending on the specific item, even when measuring materials of the same type. For example, apples have a pH of approximately 3.5, but different types of apples may have a pH that is closer to 4 or closer to 3.

What substances have a neutral pH?

True neutral pH is 7, which is the pH of pure water. Most substances fall on either side of the pH scale, though some solutions are closer to neutral than others. For example, milk and butter are very mildly acidic in comparison to other substances, and human blood is mildly alkaline.

What substances have an acidic pH?

Any substance with a pH below 7 is considered acidic. Coffee, bread and bananas are examples of substances that are mildly acidic with pH levels of around 5-6. Vinegar and lemon juice are examples of high acidity between 2-3 pH, while hydrochloric acid (HCl) is 0 pH.

What substances have an alkaline pH?

Any substance with a pH above 7 is considered alkaline. Eggs and baking soda are examples of mildly alkaline substances, ranging from 8-9 pH. Ammonia and lime are examples are high alkalinity with pH levels of 11 and 13. Sodium hydroxide (NaOH), often used in drain cleaners, is 14 pH.

Buy digital pH testers for schools at Hanna Instruments

Hanna stocks easy-to-use, practical scientific instrumentation that is suitable for use in all educational settings, from primary and secondary school classrooms to sixth forms, colleges and university laboratories.

Our range of testers is an ideal choice for educators and teachers covering all ages, including pocket pH testers, advanced meters for use in the field and research-grade benchtop meters utilised in a wide range of different scientific environments.

Shop the range online today or contact our team directly to discuss your requirements.