Osmosis - some examples from everyday life

The principle of osmosis is not always easy to understand. In order to simplify matters, some examples from everyday life have been collected in this article, which illustrate the effects of osmosis on the basis of everyday occurrences. Osmosis encounters us more often in everyday life than we generally perceive. And the reverse osmosis under pressure, reverse osmosis, is used to purify water.

Necessary requirements for osmosis

It takes three things to complete osmosis:

  • a so-called semi-permeable (ie only permeable on one side) membrane
  • a high concentration of something on the one hand
  • a low concentration of something on the other side.

Semipermeable membranes often occur in nature without us consciously perceiving them. The shells of fruits are, for example, a semi-permeable membrane - not in all fruits, but in very many, especially in the soft and juicy fruits. Cherries are a good example of this

An example with cherries

The puzzle: why do cherries burst in the rain?

The principle is completely clear. Inside the cherry, many substances are dissolved, there is a high concentration, including sugar and other substances. In rainwater virtually no substances are dissolved, it is almost distilled water.

It builds up an osmotic pressure between the inside and the outside of the cherry. This osmotic pressure causes rainwater to enter the cherry in an effort to dilute the high concentration inside. Of course, this does not succeed, and as a result, more and more rainwater penetrates into the cherry - until it bursts.

The exact reversed effect you experience when you put fruits in sugar. What is happening?
Right. The juice comes out. The concentration of sugar on the outside of the shell is suddenly much higher than inside the fruit. An osmotic pressure builds up as the concentrations on both sides of the shell will equalize. Juice exudes from the fruits to match the high sugar concentration on the outside with the lower concentration in the interior. This works well with salt.

Tips & Tricks

If one were to bring distilled water or ordinary water into the bloodstream, the blood cells would burst for exactly the same reason as the cherry in the rain. Therefore only NaCl solution may be used for infusions (physiological saline)

Video Board: Why is osmosis important ?