Acid vs. Base: What's the Difference?
Acids and bases are chemical opposites, and the difference comes down to pH and ions. An acid releases hydrogen ions (H⁺) in water and has a pH below 7; a base releases hydroxide ions (OH⁻) and has a pH above 7. Mix the two and they neutralize each other, forming water and a salt.
See the difference, explained visually.
Watch a 2-minute animated lesson comparing acid and base.
At a glance
| Acid | Base | |
|---|---|---|
| pH | Below 7 | Above 7 |
| Releases | Hydrogen ions (H⁺) | Hydroxide ions (OH⁻) |
| Taste | Sour (lemon, vinegar) | Bitter (soap, baking soda) |
| Feel | Can be corrosive | Slippery, soapy |
| Example | Hydrochloric acid, citric acid | Sodium hydroxide, baking soda |
Which should you use?
Acid
It's an acid when it releases hydrogen ions, tastes sour, and sits below 7 on the pH scale — like lemon juice, vinegar, or stomach acid.
Base
It's a base when it releases hydroxide ions (or accepts hydrogen ions), feels slippery, and sits above 7 — like soap, baking soda, or antacids.
Frequently asked questions
- What happens when you mix an acid and a base?
- They neutralize each other, producing water and a salt. That's why antacids (bases) relieve acid indigestion by canceling out excess stomach acid.
- What is pH?
- pH is a 0–14 scale of how acidic or basic a solution is. Below 7 is acidic, exactly 7 is neutral (pure water), and above 7 is basic.
- Is a base the same as an alkali?
- An alkali is a base that dissolves in water. All alkalis are bases, but not every base dissolves well, so they're not exactly the same.