Spot the rotten egg
Like all products, eggs also have an expiration date, although it is not explicitly written on the cartons most of the time. When you arrive from your trip, and you get ready to prepare what should be a delicious fried egg with salt and red pepper, but the only thing that comes out of the shell is a green mucous substance that is not at all appetizing. What happened? The eggs are rotten.
All you have to do is fill two glasses of the same size with ice water and put the eggs in each glass. The one that sinks first will be the one that can still be eaten, and the other will be the one that remains on the surface, that will be the intruder that will cause you a stomachache and perhaps some infection, so throw it away as soon as possible, for heaven’s sake.