Everyday Science: Do You Know Why Any of This Happens?

The pattern in these questions is that the everyday explanation people carry around is usually one step too shallow. The sky is not blue because the sea is blue; onions do not make you cry because of the smell.

Almost every answer here comes down to one of two things: light behaving differently at different wavelengths, or a chemical reaction releasing something you did not expect. Those two ideas cover an enormous amount of daily life.