Have you ever seen hordes of small annoying midges randomly swarming overhead? Sometimes it seems that they seem to be hanging motionless in the air. On the one hand, this swarm is motionless, on the other, the insects inside it are constantly moving right, left, up, down, constantly colliding with each other and scattering again within this cloud, as if an invisible force is holding them together.
The movements of molecules are similarly chaotic, while the body retains a stable shape. This movement is called the thermal movement of molecules.
Brownian motion
Back in 1827, the famous British botanist Robert Brown used a microscope to study the behavior of microscopic pollen particles in water. He drew attention to the fact that the particles constantly moved in a chaotic, defying logical order, and this random movement did not depend on anything.the movement of the liquid in which they were, nor from its evaporation. The smallest particles of pollen described complex, mysterious trajectories. It is interesting that the intensity of such movement does not decrease with time and is not related to the chemical properties of the medium, but only increases if the viscosity of this medium or the size of the moving particles decreases. In addition, the temperature has a great influence on the speed of movement of molecules: the higher it is, the faster the particles move.
Diffusion
A long time ago, people realized that all substances in the world consist of the smallest particles: ions, atoms, molecules, and there are gaps between them, and these particles are constantly and randomly moving.
Diffusion is a consequence of the thermal motion of molecules. We can observe examples almost everywhere in everyday life: both in everyday life and in wildlife. This is the spread of odors, gluing various solid objects, mixing liquids.
Scientifically speaking, diffusion is the phenomenon of the penetration of molecules of one substance into the gaps between the molecules of another substance.
Gases and diffusion
The simplest example of diffusion in gases is the fairly rapid spread of odors (both pleasant and not so pleasant) in the air.
Diffusion in gases can be extremely dangerous, because of this phenomenon poisoning with carbon monoxide and other toxic gases occurs at lightning speed.
Diffusion in liquids
While diffusion in gases occurs rapidly, most often in seconds, diffusion in liquids takes whole minutes andsometimes even hours. It depends on density and temperature.
One example of diffusion in liquids is the very rapid dissolution of s alts, alcohols and acids, forming homogeneous solutions in a short time.
Diffusion in solids
In solids, diffusion is the most difficult, at normal room or outdoor temperature it is invisible. In all modern and old school textbooks, experiments with lead and gold plates are described as an example of diffusion in solids. This experiment showed that only after more than four years, a negligible amount of gold penetrated into lead, and lead penetrated into gold to a depth of no more than five millimeters. This difference is due to the fact that the density of lead is much higher than the density of gold.
Consequently, the speed and intensity of diffusion not least depends on the density of the substance and the speed of the chaotic movement of molecules, and the speed, in turn, depends on temperature. Diffusion is more intense and faster at higher temperatures.
Examples of diffusion in everyday life
We do not even think about the fact that every day at almost every step we meet the phenomenon of diffusion. That is why this phenomenon is considered one of the most significant and interesting in physics.
One of the simplest examples of diffusion in everyday life is the dissolution of sugar in tea or coffee. If a piece of sugar is placed in a glass of boiling water, after a while it will disappear without a trace, while even the volume of liquidpractically unchanged.
If you look around carefully, you can find many examples of diffusion that make our life easier:
- dissolving washing powder, potassium permanganate, s alt;
- spraying air fresheners;
- throat sprays;
- washing dirt from the surface of the linen;
- mixing colors by the artist;
- kneading dough;
- preparation of rich broths, soups, and gravies, sweet compotes and fruit drinks.
In 1638, returning from Mongolia, Ambassador Vasily Starkov presented the Russian Tsar Mikhail Fedorovich as a gift with almost 66 kg of dried leaves with a strange tart flavor. Muscovites who have never tried it liked this dried plant very much, and they still use it with pleasure. Did you recognize him? Of course, this is a tea that is brewed due to the phenomenon of diffusion.
Examples of diffusion in the environment
The role of diffusion in the world around us is very high. One of the most important examples of diffusion is the blood circulation in living organisms. Oxygen from the air enters the blood capillaries located in the lungs, then dissolves in them and spreads throughout the body. In turn, carbon dioxide diffuses from the capillaries into the alveoli of the lungs. Nutrients released from food diffuse into cells.
In herbaceous plant species, diffusion occurs through their entire green surface, in larger flowering plants - through leaves and stems, in shrubs and trees - through cracksin the bark of trunks and branches and lentils.
In addition, an example of diffusion in the outside world is the absorption of water and minerals dissolved in it by the root system of plants from the soil.
Diffusion is the reason why the composition of the lower atmosphere is heterogeneous and consists of several gases.
Unfortunately, in our imperfect world, there are very few people who do not know what an injection, also known as an "injection", is. This kind of painful but effective treatment is also based on the phenomenon of diffusion.
Environmental pollution: soil, air, water - these are also examples of diffusion in nature.
White clouds melting in the blue sky, so beloved by poets of all times - she is also a diffusion known to every middle and high school student!
So, diffusion is something without which our life would not only be more difficult, but practically impossible.
