The vast majority of materials around us are made up of mixtures.For example, sea water is not just water, but it is full of mineral salts that rainwater and rivers removed when passing through rocks, Besides microorganisms, sand and gases dissolved in it.Soil is a mixture of sand, mineral salts and organic materials (materials with carbon from animals and vegetables). O The very air we breathe is also a mixture of various gases, the main ones being nitrogen gas and oxygen gas. There's even water vapor in the air!
Therefore, it is very rare to find any pure material in nature. If we want to get it, we have to carry out the separation of mixtures.
There are several types of methods used in science labs and industries to separate materials that are mixed. Each method depends on the type of material we want to obtain and the type of mixture we want to separate.
Let's take the sea water itself as an example. One of the salts that are mixed with water is table salt, which is actually called sodium chloride because it is formed by the union between the elements sodium and chlorine (NaCl).
How is salt separated from water to reach our homes?The method used is called evaporation.O text Physical states of water and its changes showed that evaporation is the slow passage of water from liquid to vapor. So, this is exactly what is done to separate a mixture formed by a liquid and a solid. It is left to rest or is heated until the liquid part evaporates, that is, it changes into a vapor or gaseous state, while the solid is obtained.
For example, imagine a mixture of salt and water. If you put it to heat on the stove, over time, the water will boil and dry, leaving only the salt in the pan.
In the case of obtaining table salt, the sea water is held in shallow tanks called saline. Over time, the heat from the sun and the wind slowly causes the water to begin to evaporate. The salt then crystallizes and is separated.
With the evaporation of sea water in the salt pans, table salt is obtained
This mixture separation process is also called crystallization, because the water has other salts mixed with it. But table salt crystallizes first, so before the other salts also crystallize, it needs to be separated.
However, in these types of mixture separations, water is lost. What if we wanted to use water for another purpose? How would you go about getting salt and liquid water?
In this case, scientists use another more elaborate method of separation of mixtures, which is the distillation, in which the water that evaporates goes to a device called condenser. Again, the text Physical states of water and its changes also explained that the condensation it is the passage from the gaseous state (or vapor state) to the liquid state. Inside the bottle in the figure below there is condensation of water vapor:
Condensation of water vapor inside the bottle
So, in distillation, when the water vapor that has been separated from the mixture reaches this device – the condenser – the steam is cooled and the water becomes liquid again. In this way, it is possible to obtain salt on one side and water on the other side.
By Jennifer Fogaça
Graduated in Chemistry
