A whitish-yellowish block. Could be cheese. Could be soap. How can you be sure?
The answer can have definite consequences. Eating soap is unpleasant and bubbly. Cleaning yourself with cheese is ineffective, and attracts mice. In these and many other ways, being able to distinguish between cheese and soap is crucial to your continued happiness. But how do you do it?
Fortunately, it’s simple to tell them apart if you know the secret. All you need is an electron microscope to inspect the molecules of the substance in question. Cheese contains many amino acid molecules (see Figure A). Soap, on the other hand, contains sodium dodecyl sulfate molecules, also known as sodium lauryl sulfate (Figure B) – called Laurie by its friends and known to the police under other aliases.
It’s easy to remember which is which, when you realize that the long wiggly tail of Laurie accounts for the scrubbing action of soap, whereas the happy hexagon explains the happy feeling in your tummy from eating tasty cheese.