Vinegar (pH 3) and Soap/Bleach (pH 12/13) are in the opposite ends of the pH scale but are both used to clean surfaces effectively. Can someone explain why this is so?

Question

What is in vinegar that makes it clean well, and what is in soap/bleach that makes it clean well despite both being in opposite ends of the scale? And is it advisable to use one before the other for maximum effectiveness?

In: Chemistry

Answer 1

Cleaning agents can work in various ways. You might want to destroy germs, pick up oil, remove stains, and so forth. Different cleaning agents leverage different chemical properties to achieve these goals to varying degrees. You also might want them to be mild so that you don’t accidentally poison yourself, or at least don’t need to be careful with them.

* The germs or grime stuck to your surfaces is likely at close to a neutral pH. High or low pH may disrupt those things. For instance, both acids and bases can break down cells.
* Soap has another feature, in that it binds to oils and water, and so it helps lift off oil or grease things when you wipe/rinse it away with water.
* Vinegar won’t do too much for cleaning up an oil spill, but it has the bonus of being very safe. We can safely drink vinegar (and some recipes will even call for it), so if you get some on your skin or accidentally spray some in your mouth, you’ll be fine.
* Chlorine and peroxide based bleaches have another feature, in that it can ‘oxidises’ things. This is to do with about taking electrons from molecules, which changes their chemistry. (Combustion and rusting are other types of oxidation reactions.)
* I think there are also sulphur based bleaches which can ‘reduce’ things. This is also about electrons, but giving them to molecules, so it is the opposite of ‘oxidation’. (Photosynthesis and smelting aluminium ore into metal are some examples of reduction.)
* Being ‘oxidised’ or ‘reduced’ are big chemical changes, and cells typically cannot survive large amounts of their molecules undergoing these changes. For instance, consider the difference between the chloride in tablesalt (safe to eat), and chlorine gas (deadly to breath): the difference is whether the chlorine atoms have been oxidised or reduced.