There are various methods used to separate components of mixtures & compounds. Since you’re studying the methods to separate the components of a mixture, I assume you’re already familiar with both terms. However, I’d help you with a brief introduction.
Mixture
When two or more substances are mixed to don’t lose their original properties, the material so formed is called a mixture—E.g. saltwater, air, soda, etc.
A mixture can be further classified as:
- Homogeneous
- Heterogeneous
Homogeneous mixture- when the components of a mixture dissolve completely into each other, it’s called a homogeneous mixture. For example, when we add salt to the water, they mix completely & we cannot identify them separately. It is also known as a uniform mixture since the constituents are distributed uniformly throughout.
Heterogeneous mixture- when the solute & the solvent do not mix completely & we can see them with our eyes. For example, when oil is mixed with water, they do not mix completely & we can see them individually in the mixture. It is also known as a non- non-uniform mixture since the constituents are distributed unevenly.
There are three types of a mixture based on the size of their particles:
- Solution- it is a homogeneous mixture of two or more substances. It is transparent.
- Suspension- it is a heterogeneous mixture of fluid & a solid substance. The solid particles may be visible to the naked eye. It is translucent.
- Colloid- colloids lie somewhere between solutions & suspensions. They are usually heterogeneous with some properties of homogeneous mixtures.
Compounds
Two or more types of atoms combine in fixed proportions to form a chemical compound. E.g. water, methane, glucose, etc.
Depending on the type of bonding, compounds can be classified as:
- Molecules-are a group of two or more atoms held together by covalent bonds. They’re electrically neutral.
- Ionic compounds-are made up of ions held together by ionic bonds.
- Inter-metallic compounds-are solid phases formed by two or more metallic elements (with optional non-metallic elements). They’re held together by metallic bonds.
- Complexes-elements held together by coordinate covalent bonds.
Now that you are acquainted with mixtures & compounds.
Let’s learn the various separation techniques to get their components.
There are many ways to separate the constituents of the mixture, but here we’ll learn a few:
- Handpicking
- Filtration
- Centrifugation
- Distillation
- Threshing
- Winnowing
- Sieving
- Sedimentation
- Evaporation
- Chromatography
- Magnetic Separation
Handpicking- separating substances with hands, for example, removing pebbles from the wheat.
Filtration- it is used to separate insoluble substances from the liquid. The solids are removed from the liquid using filter paper or other materials. E.g. making filter coffee, filtering the tea.
Centrifugation– it is used to separate insoluble substances from the liquid when they can’t t be separated through filtration. The centrifuge consists of the rotor on which the tubes are fitted. The mixture is poured into the tubes & the rotor is used to rotate the tubes horizontally.
On rapid rotation, due to the centrifugal force, the denser insoluble particles separate from the liquid. When the rotation stops, the solid particles deposit at the bottom of the centrifuge tube & the liquid remains at the top. Uses, used for blood and urine tests, used to separate butter from cream.
Distillation- it is used to separate two or more pure & miscible liquids.
The process of distillation includes vaporisation, condensation & isolation, respectively.
The mixture is first heated so that the liquid with the lowest boiling evaporates & turns into gas &/ or vapours, separating it from the mixture. Then it’s passed through a condenser & collected in the form of a liquid.
There are two types of distillation:
- Simple distillation-is used to separate two or more liquids with boiling points far from each other.
E.g. Distillation of alcohol.
- Fractional distillation-it is used to separate two or more whose boiling points are in a close range.
It is the same as simple distillation except a fractionating column placed in between the condenser & the distillation flask—E.g. Separation of fractions from petroleum products.
Threshing- it is usually used to separate wheat grains from the stalks. The stalks are dried after harvesting & then beaten on the ground to separate the grains from the stalks.
Winnowing- it is used to separate chaffs & husks from the grains. The farmer drops the grains from a certain height so that the husks & chaffs are blown away with the winds & the grains fall on the earth.
Sieving- after the grains are collected, some dirt & pebbles are also collected along with them. That dirt & pebbles are removed with the help of these test sieves. The grains are put into a sieve & the sieve is then shaken so that the smaller-sized dirt passes through the sieve & the large-sized grains remain on the sieve.
Sedimentation- it is used to separate solids from the liquid. The liquid is allowed to rest so that the heavier particles of solids settle down at the bottom of the liquid and the pure liquid above can be collected. For example, separating mud from water.
Evaporation- it can be used to separate miscible liquids or soluble solids. For example, to make salt. The ocean water is evaporated so that the water evaporates in the form of gas & the solid particles of salt remain behind. Also, it is one of the steps in the process of distillation, as we’ve learned above.
Chromatography- is used to separate the different components in a liquid mixture. The sample is first dissolved in a particular solvent called the mobile phase. The mobile phase may be a liquid or gas. The mobile phase is then passed through the stationary phase. The stationary phase maybe a piece of chromatography paper or a solid packed in a glass plate.
The various components of the mixture travel at different speeds, which cause them to separate. There are different chromatographic techniques such as column chromatography, paper chromatography, TLC, and gas chromatography.
Paper chromatography is used as the stationary phase and a liquid solvent as the mobile phase. The mixture sample is placed on a spot on the paper, and the paper is then carefully dipped into a solvent. Capillary action causes the solvent to rise the paper. The components of the mixture rise that different rates and therefore are separated from one another.
Uses: To separate drugs from the blood.
Magnetic Separation- as the name suggests, strong magnets separate substances with magnetic properties. If the mixture has at least one element with magnetic properties, then this method can be used.
Extraction- a mixture of two immiscible liquids is used to separate the components of a mixture. For example, if we want to separate salt from oil, then we can add water to it & shake it so that the salt gets dissolved in the water, then we can let it rest for a while so that the oil & water separate & then we can separate oil from the water by decantation.
Decantation- it is used to separate immiscible substances such that the top layer can be poured into another vessel. For example, sand & water, oil & water. We let the water rest for some time so that the sand collects at the bottom & then we can pour the water into another container.
Conclusion
Hope you can now understand the different types of separation techniques for mixtures and compounds.
