All About pH

Contributor: Hannah Brooks. Lesson ID: 12191

If you have a swimming pool, fish tank, or vegetable garden, you may be familiar with the pH scale. Heartburn might clue you in as to acids, too. What does the pH scale measure, and what is its value?



learning style
personality style
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


Why do you think your parents told you not to suck on lemons?

Lemons are a citrus fruit, which means that they contain a high level of acidic juice.

That is why we are often told to avoid biting into lemons, because acidic juice eats away at the enamel covering your teeth.

  • What do you think acidic means?

Substances can be classified as acidic, basic, and neutral. Maybe you have heard some of these terms in TV commercials or in doctor's offices.

  • Have you wondered what these terms mean or how they get defined?

Acids are solutions that have a high concentration of hydrogen ions, which carry a positive charge. An ion is any atom that has a charge, either negative or positive. Examples of some common acids are acetic acid, which is found in vinegar, hydrochloric acids, which can be found in your stomach, and sulfuric acid, which can be found in car batteries. Acids are an integral part of chemical interactions, but they can also be very dangerous! They are very corrosive, which means they break down substances through chemical reactions.

Bases are kind of the opposite from acids — they have low hydrogen ions and high hydroxide ions. Hydroxide is just a bond between one oxygen atom and one hydrogen atom.

periodic table

You can find both of those elements in the periodic table of elements! Bases include ammonia, which can be found in Windex, and sodium hydroxide, a cleaning product found in Magic Erasers! Bases can be just as dangerous as acids, causing damage to property and skin through chemical reactions.

Can you guess what the relationship is between hydrogen and hydroxide ions in a neutral solution? If you guessed "equal," you are right! Neutral substances have a good balance between both types of ions. Water and blood are two good examples of neutral substances!

We use terms like "acid," "base," and "neutral" to talk about solutions, but we can also refer to these solutions using the pH scale. The pH scale is a measure of the concentration of hydrogen ions or acidity. It ranges from 0 to 14, and includes most common solutions.

  • So, where do acids and bases fit on this scale?

Acids range from 0 to 6, and bases from 8 to 14. Substances around 7 are defined as neutral.

pH Scale

Discuss the following questions with your teacher or parent:

  • Are there substances on the image above that you find in your kitchen?
  • The pH scale is used to classify and identify solutions all around us! What other acids and bases can you name?
  • Do you have questions about how the pH scale is used in science?

In the Got It? section, we will learn more about different acids and bases.

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