Mixture can be separated by physical means

Separation process overview

Separation processes in chemistry or physics help to separate two or more substances from one another. This article explains these processes and deals with terms such as decanting, floating, distillation, extraction, etc. You are in the Basics of Chemistry section.

In this article we dealt with separation processes in chemistry and physics. I will go into the important fundamentals of chemistry again in a moment to explain exactly these relationships in an understandable manner. However, if you have any major gaps in your previous knowledge, I advise you to read the following articles first:


Separation process basics

Separation processes are used in chemistry and physics to separate two or more substances from one another. A simple example: you throw noodles in water to cook them. If the noodles are soft, you can use a sieve to separate the water from the noodles. However, it is often not as easy as with pasta.
In order to be able to carry out a separation process, one must first be aware that one is dealing with a mixture of substances. In this context, two important terms are important: The homogeneous mixture of fabrics and the heterogeneous mix of fabrics. One speaks of a homogeneous mixture when one cannot visually distinguish the substances in this mixture. A heterogeneous mixture, on the other hand, is immediately recognizable as such. Or to put it another way: With a heterogeneous mixture, you can see at first glance that there is a mix of substances.
For example, if you have a liquid and want to know whether you have a pure substance or a mixture, you can carry out chemical and physical tests. Example: You cannot see whether you have pure water or salt water. One way to find out is to heat the liquid. The boiling temperature curve of pure water is different from that of salt water.


Different separation processes

If you want to separate a mixture into individual substances, you have to choose one of many separation processes. The following is a brief overview of some separation processes. In practice, however, a lot of experience and even more specialist knowledge is often required in order to be able to carry out separations successfully.


Filtration is one of the mechanical separation processes. The mixture to be separated passes through a filter made, for example, of paper or textile fabric. It is important to know that only parts are retained that are larger than the pore size of the filter. A good example of a filter is the coffee filter.


When decanting, you wait until (solid) substances have settled at the bottom and then carefully pour off the top (liquid) layer. Decanting has the disadvantage that the separation is not carried out completely. You only pour off part of a substance and in the end you usually still have an impure mixture.


Sedimentation is the deposition of particles from liquids or gases under the influence of gravity or other forces (e.g. centrifugal force). This is how the sand trap is carried out in sewage treatment plants.


Distillation is a thermal separation process to separate a liquid mixture of different substances that are soluble in one another. The prerequisite for using the process are different boiling points of the substances to be separated. Typical uses of distillation are burning alcohol and distilling petroleum in the refinery.

Magnet separation:

When separating magnets, mixtures of magnetic and non-magnetic substances are separated by their magnetizability. The separation effect is based on the different magnetizability of the various substances. Magnetic matter is pulled out and non-magnetic matter remains where it is.


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