Let’s learn about acids and bases

These molecules are about give and take

This pH measure uses treated paper strips that change color when exposed to acidic or basic solutions. A scientist can then look at the color to determine the pH of the chemical they are testing.

alina_hart/iStock/Getty Images Plus

Acids and bases are different types of chemicals that like to trade particles. In a solution, an acid is a chemical that will release hydrogen ions — atoms with a tiny positive charge. Those positively charged particles — also called protons — react easily with anything that will take them. Acids are sometimes called proton donors.  

Bases are chemicals that contain oxygen atoms bound to hydrogen atoms. This pair is called a hydroxyl group and has a tiny negative charge. Bases react easily with positively charged particles, and they are sometimes called proton acceptors.

Because acids and bases react so easily, they play important roles in chemical reactions. They also play important roles in our lives — and the lives of many organisms. For example, we taste acids as sour and bases as bitter. The sourness of lemonade and the bitterness of dark chocolate come from our tongue sensing the acids in lemons and the bitter compounds in cocoa. While we might enjoy some of these flavors, having this sense is important for detecting potentially dangerous substances.

In the ocean, acids and bases are even more critical. Mollusks in the ocean rely on certain chemicals to build their shells. Sharks rely on a specific pH in water for their hypersensitive noses. As humans produce more carbon dioxide from fossil fuels, some of it ends up in the ocean — where it acidifies the water. A more acidic sea means animals have a harder time building their shells.

To know if something’s an acid or a base, scientists use a pH scale. This scale runs from zero to 14. A pH of seven is neutral; this is the pH of pure water. Anything with a pH lower than seven is an acid — from lemon juice to battery acid. Substances with a pH higher than seven are bases — including oven cleaner, bleach and your own blood.

Acids and bases can be strong or weak. Both can be useful and both can be dangerous. Here’s why.

Want to know more? We’ve got some stories to get you started:

Study acid-base chemistry with at-home volcanoes: Baking soda volcanoes are a fun demonstration, and with a few tweaks they can be an experiment, too. (10/7/2020) Readability: 6.4

Explainer: What are acids and bases?: These chemistry terms tell us if a molecule is more likely to give up a proton or pick up a new one. (11/13/2019) Readability: 7.5

Tongues ‘taste’ water by sensing sour: Water doesn’t taste like much, but our tongues need to detect it somehow. They may do it by sensing acid, a new study shows. (7/5/2017) Readability: 6.7

Explore more

Scientists Say: Acid

Scientists Say: Base

Explainer: What the pH scale tells us

Explainer: What are logarithms and exponents?

Shell shocked: Emerging impacts of our acidifying seas

Is ocean acidification knocking the scents out of salmon?

Word find

Got cabbage? This purple veggie is all you need to make your own pH indicator. Boil cabbage in water and then test the chemicals around your house to see which are acidic and which are basic.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

More Stories from Science News Explores on Chemistry