Grade 6 → Separation of mixtures ↓
Separation methods
In everyday life, we encounter mixtures everywhere around us. A mixture is made up of two or more substances that are physically combined. Unlike chemical reactions, the substances in a mixture retain their own properties. Mixtures come in many forms, ranging from air into which we add gases such as nitrogen and oxygen, or the salad you can make from a variety of vegetables.
The challenge with mixtures comes when we need to separate them into their pure components or we want to separate them. Various methods can be used to separate mixtures, and the choice of method depends on the nature of the mixture and the properties of the components. Here we will explore several common methods of separation, explain how they work, and provide examples to help you understand the process.
1. Handpicking
Hand picking is a simple method of separating solid components from a mixture. This method is best used when the mixture contains a relatively small number of large-sized components that differ from the other components. As the name suggests, you can use your hands to pick out the unwanted material.
Example: Imagine you have a bowl full of sand with some pebbles mixed in. You can easily pick out the pebbles using your fingers.
Hand picking is not suitable for large quantities, nor is it effective when the particles are very small or of uniform size.
2. Strainer
Sieving is done using a sieve, which is a device with tiny holes, to separate components based on size. This method works when the mixture has components of varying sizes.
Example: In cooking, a sieve is used to sift flour to remove lumps and make the flour smooth and fine. Similarly, in construction, a sieve with an iron mesh separates stones from sand.
3. Threshing
Threshing is a method used to separate grains from the stalks. It is commonly used in agriculture to obtain grain after harvesting cereals such as wheat.
This process involves separating the grain from the chaff by beating the stalks. In traditional cultures, this could be done by hand or with the help of animals. Nowadays, machines called threshers do this work.
Example: After harvesting wheat, threshing is done to separate the wheat grains from the stalks.
4. Winnowing
Winnowing is a method used to separate lighter components from heavier components using air or wind. This technique is often used in the agricultural sector to separate chaff from grain after threshing.
In this method a basket is used. When the mixture is dropped from a height, the wind carries away the lighter particles, and the heavier particles fall straight down.
Example: After threshing, wheat grains are winnowed to separate from the chaff.
5. Strainer
Sieving is done using a sieve, which is a device with tiny holes in it, to separate components based on size. This method works well for separating larger solids from finer-grained components.
Example: When cooking, a cook might sift flour to ensure it is free of lumps. Also, in construction work, sand is sifted to remove large stones.
6. Sedimentation and decantation
Sedimentation and decantation are combined methods used to separate insoluble particles from a liquid. Sedimentation involves allowing the heavier particles in a mixture to settle to the bottom of a container. Once settled, the liquid can be poured off, which is called decantation.
Example: When muddy water is left undisturbed, the muddy water (being heavier) will settle at the bottom, allowing clear water to flow out.
7. Filtration
Filtration involves using a filter to separate solid particles from liquids or gases. The filter traps the particles and allows the liquid or gas to pass through. This method is useful when separating mixtures with insoluble solids.
Example: Filter paper is used to separate coffee residue from brewed coffee. Similarly, air filters in air conditioners filter out dust particles.
8. Evaporation
Evaporation is the process of changing a liquid into a vapor to separate the solute from the solvent. This method works well for solutions.
Example: When preparing salt from seawater, the water is left to evaporate, leaving salt crystals behind.
9. Distillation
Distillation is a process that uses both evaporation and condensation to separate substances. It is effective for separating components based on different boiling points.
Example: In the distillation of alcohol, the mixture is heated. The alcohol having lower boiling point evaporates first. The vapours are then cooled and collected separately.
Water (H 2 O)
Ethanol (C 2 H 5 OH)
10. Magnetic separation
Magnetic separation uses magnets to separate magnetic substances from non-magnetic substances. This method is used in industry to separate iron from other substances.
Example: Garbage plants use magnets to separate iron pieces from waste.
Conclusion
Various methods of separation are available to us depending upon the properties of the elements present in the mixture. The choice of method depends upon the form and nature of the mixture we are dealing with. Methods such as hand picking, sifting and filtering are simple and suitable for everyday use. Other methods such as distillation and magnetic separation are used for industrial and commercial purposes. Understanding these methods helps in understanding how things are separated naturally and artificially in our environment.
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