Separation Techniques part 2

Olawunmi Omosanya - Wed, 26th June, 2019 @ 06:15: AM

Topics in Chemistry

Salts and Types of Salt in Chemistry Separation Techniques Separation Techniques part 2 Separation Techniques part 3 Physical Change, Chemical Change, Element, Compound and Mixture Electrolysis, Electrolyte, Electrode, Anode and Cathode Grahams law of diffusion Physical Properties of Metals Daltons Atomic Theory and its Modifications Periodic table and Classification of Elements

Academic Questions in Chemistry

The only metal that exist as liquid at room temperature is _____.

  1. Nickel
  2. Duralumin
  3. Mercury
  4. Lead
  5. Titanium
  6. Cesium

ANSWER is Mercury

Mercury is a liquid metal at room temperature. Its chemical symbol is Hg. The name mercury comes from its Greek name, hydrargyrum, which means "liquid silver" .  Mercury has an atomic number of 80. Please read on the periodic table of elements here

The element mercury is also considered to be named after the fastest-moving planet in the solar system. You can read on solar system here.


Separation Techniques:

Please read part 1 here


(5) Centrifugation

Centrifugation involves the use of a device called centrifuge to separate the lighter portions of a mixture from the denser portions through the spinning action of the centrifuge. Blood is a mixture and its components can be separated via centrifugation. 

Blood is considered a mixture because it is composed of liquid plasma and solid cells.

You may read on the red blood cells here

Image Credit: Microbiology Notes

Using blood as an instance, the test tubes containing the blood are inserted into the centrifuge. The centrifuge begins to spin/rotate when it's switched on; and this is allowed to continue for about 5 to 10 minutes. On bringing out the test tubes from the centrifuge, two different layers will be observed. These are:

  • The lower layer composed of solid cells that had sediment.
  • The upper layer containing the less dense plasma will be seen above it.

Next, the plasma can then be carefully decanted from the test tube. (Please see decantation above).

Below are some types of centrifugation
  • Differential Pelleting (differential centrifugation)
  • Isopynic Centrifugation
  • Density Gradient Centrifugation
  • Rate-Zonal Density-Gradient Centrifugation


(6) Sublimation

Matter exists in three states. These are:

  • Solid
  • Liquid
  • Gas

You may read on solid, liquid and gases here.

On heating a solid, it changes to liquid. If we continue heating, the liquid changes to gas. This is the usual sequence, however, in sublimation the heated solid does not pass through the liquid phase; instead, it changes to gas directly.

Sublimation is a process whereby a heated solid changes directly to gas without passing through the liquid phase

Such solids are said to sublime.

Examples of solids that sublime are ammonium chloride (NH4Cl), iodine crystals, sulphur, solid carbon(IV)oxide or dry ice, arsenic and naphthalene.

With regards to separation of mixtures, sublimation is used to separate two salts (or solids) in which one sublimes and the other does not. An example is a mixture of common salt and iodine crystals.


(7) Distillation

Distillation is a technique used to separate two or more miscible liquid that have different boiling points. (The boiling points of the different liquids may not be at a close range). The mixture of water and ethanol is a typical example since they are both miscible and have different boiling points. The mixture of water and acetone can also be separated via distillation.

Water boils at 100oC

Ethanol boils at 780C

Image Credit: Science Struck

To carry out distillation, the mixtures of both liquids are heated until the one with a lesser boiling point (ethanol in our instance) vapourizes or changes to vapour. The vapour is collected and cooled by passing it through a condenser. The condenser compresses this vapour into liquid as our ethanol is now collected as a distillate.

Think of a distillate as a liquid collected from the process of distillation after it has been passed through a condenser.

When we have two liquids of different boiling points, the liquid with a lesser boiling point is said to be more volatile while that with a higher boiling point is said to be less volatile

Distillation can also be used to:

  1. Separate a solid and a liquid: The liquid evaporates and is collected and condensed while the solid remains in the container.
  2. Purify liquid: This is true since only the pure liquid will vapourize leaving behind the solid impurities in the container.

Please read part 3 here

Amazing facts in Chemistry

Gold and copper are the only two non-silvery colored metals. Please read some interesting facts about gold here

Copper is the only metal that is naturally antibacterial. This is why you would see some children carry copper water bottles to school

Water actually freezes faster when it’s warm than when it’s cold

Most element in their pure state exists physically in different forms. For instance, pure carbon can exist as both diamond and graphite. This phenomenon is called allotropy.
Please read on modification of Dalton's atomic theory here.

If you pour a handful of salt into a full glass of water, the water level will go down rather than overflowing the glass.

Similarly, if you mix half liter of water and half litre of alcohol, the total volume of the liquid will be les than one litre


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