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What is an Alkali? - Lesson for Kids

Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

This lesson gives a glimpse at what it means for a substance to be alkali. We will look at the meaning of alkali as well as learn about the pH scale and its importance.

What does Alkali Mean?

Bananas are usually sweet, but if you have ever bitten into a very unripe banana, you probably noticed a bitter taste right away. That bitter taste can be a clue that something is an alkaline substance.

The opposite of an alkali is an acid. Instead of a bitter taste, acids tend to have a sour taste. Things such as lemons and vinegar are acids, or acidic.

We can tell whether a substance is an alkali or an acid by knowing its pH. pH is measured with the pH scale; this scale ranges from 0-14, and these numbers tell us if a substance is an alkali or an acid.

Pure, distilled water has a pH of 7. This is called neutral and is right in the middle of the scale. Any substance that has a pH higher than 7 is an alkali (or alkaline) substance, which is also called basic. Any substance that has a pH lower than 7 is an acid.

Why is a Substance Alkali?

So we already know that pH is a scale that ranges from 0-14 and tells whether a substance is an alkali or an acid. However, we don't really know why. Let's take a closer look now.

The pH of a substance depends on how atoms are arranged and combined in the substance. Atoms are the smallest unit and make up every object and substance in the universe.

Remember that pure water is right in the middle of the scale and has a pH of 7. This means that it contains an equal amount of hydrogen atoms (H+) and hydroxide atoms (OH-). When a substance has more hydrogen atoms (H+), it is an acid. When a substance has more hydroxide atoms (OH-), it is an alkali, or basic.

Examples of Substances with Different pH
pHscale

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