pH is a quantitative measure of acidity or basicity in an aqueous or liquid solution.
- A solution with a pH less than 7 is acidic.
- A solution with a pH greater than 7 is considered basic (or alkaline)
The pH scale is logarithmic and inverse, and indicates the concentration of hydrogen ions in a solution.
- This means that a low pH has a high concentration of hydrogen ions in a solution.
If you take A-Level Chemistry, then pH will come up quite a lot! You'll need to remember the pH equation. In Biology, all you need to know is the colours that universal indicator will go depending on the acidity or basicity of a substance, something you'll have covered at GCSE.
But if you don't remember, here's a picture below to help you with the colours from the indicator, and an average pH for different solutions you might come across:
[caption id="attachment_10153" align="alignnone" width="236"]
Average pH of common solutions (from US Environmental Protection Agency, 2014 - CC-BY-ND 4.0)[/caption]