pH: The Acidity Scale

chemistry · acids · water · measurement

A numbered scale. pH uses numbers from 0 to 14 to measure how acidic or basic something is. The lower the number, the more acidic (sour) it is, and the higher the number, the more basic or alkaline (soapy) it is.

Acids are sour. Acidic solutions have low pH numbers, like lemon juice or vinegar. These liquids taste sour and can fizz or bubble when they react with certain materials.

Bases are slippery. Basic or alkaline solutions have high pH numbers, like baking soda dissolved in water or soap. These liquids feel slippery and can clean things really well.

Hydrogen is the clue. The 'H' in pH stands for hydrogen, which is the smallest atom and shows up in all acids and bases. Scientists use pH to measure how much hydrogen is involved in making something acidic or basic.

Perfect in the middle. A pH of 7 is neutral, which means it's neither acidic nor basic, like pure water. Most living things need their environment to be close to neutral or slightly basic to survive.