Science: A Field Of Wonder/Separating Mixtures

Some people still mine for gold. The picture shows the technique called panning. Panning for gold is a separation process developed by early people. How is gold dust separated from sand and other particles in panning? What technique is used to separate gold from other particles?

Separating Mixtures

Various substances are manufactured every day by separating mixture into their components. Bicycles, computers, and even cell phones are produced from materials that are separated from the ground. Crude petroleum is refined to produce fuels, plastics, and edible oil-based products. Many food items and drinks that you consume every day, from table salt to diet cola, are made using processes that involve separating mixtures.

Some methods of separating mixtures can have a positive impact on the environment. Filtering is an example of a separation method with positive consequences. Air and water filters are the two most common types of filters are the two most common types of filters to make water and air clean.

What are the different ways of separating mixtures? Components of a mixture are often easy to separate. Common methods of separating mixtures include picking by hand, decantation, filtration, evaporation, magnetic separation.

Filter - a device or material that traps some substances and allows others to pass through

Picking by hand

You have read that sometimes the properties of substances in a mixture are easy to see and easy to handle. You can separate those substances by hand. Separating the parts of a mixture is only useful when the particles are large enough to be seen clearly.

Mixtures made of solids are often easy to separate by hand. For example, you can pick raisins out of bowl of cereal with your fingers. You can also separate some liquid mixtures and liquid-solid mixtures by hand. For a mixture of rocks and water, you can easily pick out the rocks in water.

Using Tools

If the parts of a mixture are hard to see or to hold, you use tools to separate them. By using tools, you also save time. Below are ways of separating mixtures with the use of tools/

Decantation

Decantation is the careful pouring out of a liquid leaving the undissolved substances at the bottom of the container. It is a simple and fast means of separating liquid from heavier solid particles. The heterogeneous mixture is allowed to stand for sometime to allow the heavy solid particles. The heterogeneous mixture is allowed to stand for sometime to allow the heavy solid particles to settle at the bottom of the container. The liquid called the decantate is then slowly poured out to separate it from the solid. However, this method cannot be used if the solid particles are light and fine. For sand and water mixture, you can separate the water from sand, the residue, through decantation.

Decantate - a liquid poured off from the mixture while leaving the solid materials

Filtration

Mixtures of liquid and solid can also be separated using filtration. This is ideal for separating solid particles that are light and fine from liquid. Filtration is done with the aid of a filter paper which helps separate the solid particles from the liquid called filtrate. The solid separated by the filter paper is called the residue. The example of a filtration setup is shown in the figure below.

Filtering Liquids

Waste water treatment involves the use of filters that separate impurities from water. This process helps make it possible for municipalities to provide large amounts of treated water for domestic use. Waste water is filtered for consumption at home and this is an example of a positive impact of filtration on society and the environment.

Water purification uses very fine filters to separate dirt and some bacteria from water. Water filters can be used to improve the quality of water. Commercial water filters are often used to remove impurities from the water during the production of different food products.

Filtering Air

Many people suffer from asthma or allergies that made worse by breathing air contaminated with dust, pollen, and other matter produced by combustion of fuels. Smog can make it impossible for some people to leave their house. Filters can significantly improve the quality of air both inside and outside the home, making it healthier for people to breathe. For example, air filters are used in air conditioners to help clean the air inside the home. Air filtration has a positive impact on society and the environment..

Air filters are also used in building ventilation systems to ensure that the air is free of dust and other substances.

Evaporation

There are some materials that mix completely and evenly with water. One example is when you dissolve salt in water. How can you dissolve salt in water? How can you remove the salt from the water? You can separate a mixture of salt and water through evaporation. If you allow the water to evaporate, the salt will be left behind. The water that evaporates is called water vapor and the salt that remains is the residue.

For many years, people living near seas have used the heat from sunlight to evaporate seawater and obtain salt. Seawater flows into a large, low-lying area called a salt pan, which is surrounded by dikes. When the water has evaporated, the remaining solid is about 96 percent salt. Pangasinan is a province in Region I known for its quality salt product.

Distillation

Unlike evaporation where water evaporates and cannot be collected, distillation can collect evaporated water though the cooling and condensation of water vapor into a separate container. The salt does not evaporate and so it stays behind.

distillate - the vapor collected during a distillation process

Mixtures of liquid samples can easily be separated through distillation. This separation technique is based on the differences in boiling point of the components of the mixture. A distillation in set-up is seen below.

Another useful method of separating mixtures is the fractional distillation. This is used to separate different substances that make up crude petroleum oil based on differences in their boiling points The picture below shows an oil facility that uses fractional distillation to refine petroleum.

fractional distillation - the process of separating parts of a liquid by heating it gradually so that different parts become gas, then turn back into liquid that can be collected as they cool

Sieving

A sieve or strainer is a device containing tiny holes used to separate a dry mixture which contains substances of different sizes. When you put a mixture in a strainer, anything smaller than the holes falls through them. Anything larger stays in the strainer.

strainer - This is a container that has many holes of the same size. It is also called sieve.

In the beach, it would take a long time to separate the shell from sand and shell mixture. The strainer can quickly separate the sand from the shells.

Magnetic Separation

Strainers and filters separate the components of mixture by sifting the bigger parts from the smaller parts. Other tools separate mixtures, such as their different boiling parts by using properties of the materials in the mixture. A magnet, on the other hand, attracts or pulls objects that contain metal. A magnet can be used to pick up only the objects in a mixture that contain metal like iron filings. Other objects that do not contain metal are left behind.

Recyclers if solid waste often use magnets to separate metals like tin, iron, and steel from other non-metal waste products. These metals are attracted to the magnet and can be removed from nonmagnetic substance, such as wood and plastics. The metals recovered by these process can be melted down and turned into other useful products.

The industrial magnet removes steel and iron from other wastes at a metal-recycling plant.

Mining, metal extraction, oil refinement, and many other industrial processes separate useful pure substances and mixtures from other mixtures and solutions. Industries like mining focus on separating metals from rock mixtures. The resulting metals are used in manufacturing products like automobiles to airplanes. Most industries use technology to increase efficiency of metal extraction and to minimize costs and environmental impacts. Each method or process contributes some benefits to society or to the economy.