The methods of separating mixtures are procedures that allow obtaining one or more components of a mixture without modifying its chemical properties. Therefore, they are said to be based on purely physical techniques, unrelated to chemical reactions or the use of corrosive substances.
These methods are part of our day to day, whether in open field work, or within the spaces of the kitchen or a business. They are applied for the purpose of purifying or raising the quality of a product. For example, coffee is filtered to recover the precious liquid without the ground beans interfering on the palate.
In this case, it is a liquid-solid mixture, where the liquid is coffee, and the solid is ground beans. In turn, coffee itself is another mixture: a solution product of an extraction, which is homogeneous.
Thus, there are heterogeneous and homogeneous mixtures. Each of them has its own separation methods, capable of isolating their respective components. How to recognize them from each other? By the presence of more than one material phase. This means that there must be two components that can be perfectly distinguished by the naked eye.
The coffee served is a homogeneous mixture, since wherever you look at it, its appearance is liquid. On the other hand, a glass with water and linseed seeds is a heterogeneous mixture: liquid water is a material phase, while the seeds correspond to another.
Generally speaking, the separation methods for heterogeneous mixtures require more mechanical work. For homogeneous mixtures, on the other hand, they need the help of temperature. For example, evaporation is the most widely used method to separate solute from solvent in solutions.
Main methods of separating mixtures
Filtration is a separation method used to separate, in principle, liquid-solid mixtures. It needs the help of a barrier or filter that allows the liquid to pass through, but retains the solid in its tissue, which cannot pass through the tiny pores of the filter.
Filtration is normally assisted by gravity, and depending on the size of the solid particles, this can be a slow or fast process.
The word ‘filtration’ is also often used when talking about air. For example, an air contaminated with bacteria is a gaseous and homogeneous mixture. If air is passed through filters that capture bacteria, the air is said to have been filtered. This ensures that it is clean and sterile.
Filtered water is obtained thanks to the fact that its impurities and sediments are retained by special filters.
In laboratories is where the use of this method is most observed. Almost always after obtaining a precipitate or crystals, they are immediately filtered to get rid of the liquid and preserve the solid.
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