Classwork Exercise and Series (Chemistry- SS1): Standard Separation Techniques

Introduction

Most materials in our surroundings are mixtures of two or more components. Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are uniform in composition, but heterogeneous mixtures are not. Air is a homogeneous mixture and oil in water is a heterogeneous mixture. Homogeneous and heterogeneous mixtures can be separated into their components by several physical methods. The choice of separation techniques is based on the type of mixture and difference in the chemical properties of the constituents of a mixture.

Types of Separating Techniques

Various types of separation processes are: 

• Crystallization
• Filtration
• Decantation
• Sublimation
• Evaporation
• Simple distillation
• Fractional distillation
• Chromatography
• Centrifugation
• Separating funnel
• Magnetic separation
• Precipitation
• Sieving

Sieving: is used to separate solid particles of different sizes. The mixture is placed on a sieve with a mesh of a particular size. Particles smaller than the mesh size of the sieve will pass through the sieve while the bigger particles remain on the sieve. Mining industries, such as those involving diamond and gold, and Garri industries in West Africa use this method extensively.

Decantation: Decanting is the process used to separate the liquid from the denser solid(s) by simply pouring the liquid out from the beaker, e.g. a mixture of sand and water.

Filtration: is the process where a filter paper and funnel is used. It is used to separate the liquid from the solid(s), mostly suspensions. The residue is then collected on the filter paper. The liquid known as filtrate passes through the filter paper and drips into the flask. The solid that remains in the filter paper is called the residue. The substances that can be separated by this method include sand mixed with water, mixture of garri and water and a suspension of chalk dust in water.

Filtration Process

Separating funnel: is used to separate two immiscible liquids and one is denser than the other. The denser liquid will sink, thus an outlet at the bottom is opened for the denser liquid to flow out. When the denser liquid is drained, the outlet is shut. The cap of the funnel is then open for the less dense liquid to be poured out.  It is used to separate a mixture of oil and water and a mixture of kerosene oil and water.

Separating Funnel

Evaporation: is where a thermally stable mixture is heated till dryness to obtain the crystals. It can be used to recover a solid solute from a solution. In this process, the solvent is usually sacrificed. Evaporation is used in salt-making industries. 

Magnetic Separation: A magnet is used to separate magnetic substances from non-magnetic particles in a mixture. Iron filings and sulphur powder can be separated by using this method. In the steel industry this method is used to remove magnetic impurities from tin ore.

Sublimation: is the process where a solid is immediately turned to gas i.e. sublime. The gas will then be condensed. This method is used when separating two solids. This is when one solid sublimes while the other does not. Examples of such solids are iodine and ammonium chloride.