There are some substances on Earth that children of all ages seem to be fascinated with. For example, lava captures the imagination in a way that few other substances can.

The thought of molten rock flowing down a mountain consuming everything in its path gives us thrills and chills. Some children even play tag and keep away games in which certain areas are deemed to be filled with hot lava and are thus off limits.

Likewise, many children are amazed by the corrosive powers of acid. If you've ever seen a piece of metal turned to a bubbling, fizzing liquid when it encounters acid, you know the awesome chemical power acid has.

Many people don't realize that their own stomachs contain acid that's powerful enough to destroy metal. Sure, we know all about stomach acid and how it helps us digest food, but it's certainly not that powerful, is it? You bet it is!

Stomach acid, sometimes called gastric acid, consists of potassium chloride, sodium chloride, and hydrochloric acid. The concentration of hydrochloric acid in your stomach varies between 5,000-10,000 parts per million.

So exactly how strong is that stomach acid? Acids are measured on a scale known as the pH scale. The pH scale goes from 0 to 14, with 0 being the most acidic, 7 being neutral, and 14 being the most alkaline or basic (non-acidic).

Stomach acid is very acidic, with pH measurements generally ranging from 1 to 3. Those measurements put stomach acid in the same approximate category as battery acid! In fact, if you were to put a drop of stomach acid on a piece of wood, it would eat right through it.

With such powerful acid in our stomachs, what prevents it from eating a hole right through us? You can thank your stomach's epithelial cells for protecting you. These specialized cells produce a solution of mucous and bicarbonate that coats the inside of the stomach.

The bicarbonate is a base that neutralizes the stomach acid. The mucous produced by the epithelial cells also forms a physical barrier between the walls of the stomach and the acid it produces.

Of course, these systems don't always work perfectly. Some people struggle with stomach problems in which too much acid is produced. When the epithelial cells can't keep up with the task of protecting the stomach lining, stomach acid can damage the lining of the stomach, creating what doctors call gastric ulcers.

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