Why mixtures can be separated

The heat for the process comes from the sun. Once the sea water in these evaporation ponds has evaporated, the salt can be harvested.

Filtration is a separation method used to separate out pure substances in mixtures comprised of particles some of which are large enough in size to be captured with a porous material.

Particle size can vary considerably, given the type of mixture. For instance, stream water is a mixture that contains naturally occurring biological organisms like bacteria, viruses, and protozoans. Some water filters can filter out bacteria, the length of which is on the order of 1 micron.

Other mixtures, like soil, have relatively large particle sizes, which can be filtered through something like a coffee filter.

Use this resource to answer the following questions:. Skip to main content. Matter and Change. Search for:. How did goldminers search for gold? Figure 2. For example, sugar or salt dissolved in water, alcohol in water, etc. The prefix "hetero" indicates difference.

A heterogeneous mixture consists of visibly different substances or phases. The three phases or states of matter are gas, liquid and solid. A heterogeneous mixture does not have a uniform composition throughout its mass. Most materials found in nature are in the form of mixtures. In engineering, a separation process is used to transform a mixture into two or more distinct products. This is done by considering that different components of the mixture may have different properties such as:.

Depending on the raw mixture, various processes can be employed to separate the mixtures. Often, two or more of these processes must be used in combination to obtain the desired separation. In addition to chemical processes, mechanical processes are sometimes applied. In the example of crude oil, one upstream distillation operation feeds its two or more product streams into multiple downstream distillation operations to further separate the raw crude, and so on, until final products are purified.

Chemical engineers use these separation techniques to purify naturally found substances or isolate them from other substances. For example, crude oil, also called petroleum, is a complex mixture of carbon and hydrogen hydrocarbons that exists as a liquid in the Earth's crust.

Chemical engineers apply various distillation methods to purify various hydrocarbons such as natural gases, gasoline, diesel, jet fuel, lubricating oils, asphalt, etc.

Water purification is another good example of application of separation techniques. Watch this activity on YouTube. Post-Lesson Test : Administer the Mixtures Test to gauge student comprehension of the lesson content and concepts. Explain to students the distillation process for crude oil. Refer to the following source of information on the topic:. Humphrey, J. Keller II. Separation Process Technology. Industrially oriented book that includes performance, selection and scale up information.

However, these contents do not necessarily represent the policies of the NSF and you should not assume endorsement by the federal government. Why Teach Engineering in K? Find more at TeachEngineering. Quick Look. Print this lesson Toggle Dropdown Print lesson and its associated curriculum. Though chromatography is a simple technique in principle, it remains the most important method for the separation of mixtures into its components. It is quite versatile for it can be used to separate mixtures of solids, or of liquids, or mixtures of solids and liquids combined, or in the case of gas chromatography, can separate mixtures of gases.

The two elements of chromatography are the stationary phase and the mobile phase. There are many choices of stationary phases, some being alumina, silica, and even paper. The mobile phase, in liquid chromatography, can also vary. It is often either a solvent or a mixture of solvents and is often referred to as the eluant..

A careful choice of eluting solvent helps to make the separation more successful. The mixture is placed on the stationary phase. The eluant passes over the mixture and continues to pass through the stationary phase carrying along the components of the mixture. If a component in the mixture has greater affinity for the mobile phase eluant than the stationary phase, it will tend to be carried along easily with the eluant.

If another component in the mixture has a greater affinity for the stationary phase than the mobile phase then it will not be carried along so easily. Pour dirty water into the container. The layers will filter out smaller and smaller particles of dirt.

The result is clearer but not necessarily drinkable water. A centrifuge is like an extra-fast spin dryer. It spins a liquid so quickly that the particles separate out. The heavier particles sink to the bottom and the lighter particles collect at the top. Doctors separate blood samples for analysis study using a centrifuge. Scientists separate many liquid mixtures using chromatography.

The mixture is dissolved in a liquid or a gas to make a solution. The solution is put on a solid material and the substances that dissolved most easily travel farthest up the solid material.

The separated substances form bands of colour called chromatograms.