Chlorine Lesson for Kids: Facts & Properties

Instructor: Jenny Homer

Jenny has masters' degrees in public health and public administration.

Ever wonder why your eyes sometimes burn after you go swimming in a pool, but not after you take a bath? The answer is because of chlorine. Find out how this element was discovered, its characteristics, and what it's doing in our swimming pools.

What's Chlorine?

Let's pretend it's a hot summer day. You take a swim in the pool and then sit down to eat some salty French fries with ketchup. A big drop of ketchup lands right in the middle of your white t-shirt, so when you get home, the shirt goes in the laundry. A bit of bleach will get that stain out. Three things in our story - the pool, salt, and bleach - all have something in common, and that's chlorine.

As you can see from the example above, chlorine is an element in our lives. Elements are the most basic building blocks of all physical things like cars, books, or houses. As of 2017, scientists know of 118 elements, including chlorine.

Facts about Chlorine

Before talking about the properties of chlorine, let's go over how it was discovered. In ancient Egypt, people learned to get salt out of seawater. Starting in the 1600s, a number of different scientists called chemists began experimenting with salt. This eventually led to the discovery of chlorine.

Johann Rudolf Glauber heated salt in a certain way and made hydrochloric acid. In 1774, Carl Wilhelm Scheele combined hydrochloric acid with other chemicals, and got a yellow, green gas. Scheele had discovered chlorine, but thought the gas had another element called oxygen in it. When he dissolved the gas in water, he found that it took the color out of paper and flowers. In 1810, a chemist named Humphry Davy realized the gas was an element and named it chlorine because of the color. (In Greek, the word for ''yellowish-green'' is chloros.)

Today, chlorine has many uses, as you saw at the beginning of the lesson. Because it can destroy harmful bacteria, we use chlorine to clean water for swimming pools and for drinking. On its own, chlorine gas can be dangerous to people by making it hard to breathe or irritating our eyes. (That's why our eyes sometimes hurt after swimming in a pool with chlorine.)

Swimming Pool

Properties of Chlorine

All of the elements are displayed in a special table called the periodic table. To find chlorine on the periodic table, you have to look for its abbreviation, Cl. Chlorine's atomic number on the periodic table is 17, and its weight is 35.453 atomic mass units.

Chlorine is in the red box in this periodic table.

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