Science
What is Acid?
An acid is a substance that releases hydrogen ions (H⁺) in water, giving it a sour taste and a pH below 7. Acids range from mild ones in food, like the citric acid in lemons, to strong industrial ones like sulfuric acid.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains acid.
Key things to understand
- 1Acids release hydrogen ions (H⁺) when dissolved in water.
- 2They have a pH below 7 — the lower the pH, the stronger the acid.
- 3Acids taste sour (think lemon or vinegar) and can react with metals and carbonates.
- 4An acid and a base neutralize each other, producing water and a salt.
- 5Strong acids (like hydrochloric acid) ionize completely; weak acids (like the acetic acid in vinegar) only partly.
Frequently asked questions
- What's the difference between an acid and a base?
- Acids release hydrogen ions and have a pH below 7; bases release hydroxide ions (or accept hydrogen ions) and have a pH above 7. Mixed together, they neutralize each other.
- What is pH?
- pH is a 0–14 scale measuring how acidic or basic a solution is. Below 7 is acidic, 7 is neutral (like pure water), and above 7 is basic.
- Are acids dangerous?
- Some are — strong acids can burn skin and corrode metal — but many are harmless and everyday, like the citric acid in fruit or the acetic acid in vinegar.