Chemistry

Mixtures and Separation of Mixtures - part 2

len Alfred Ajibola - Wed, 26th June, 2019 @ 06:15: AM

Topics in Chemistry

Compounds in Chemistry: Characteristics of Compounds Types of Mixture: Homogenous and Heterogeneous Mixtures Mixtures: Characteristics of Mixtures Physical Properties of Matter explained with Examples Chemical Properties of Matter explained with Examples Differences between Physical and Chemical Change Ionic Theory and Electrolysis Physical and Chemical Properties of Acids States of Matter: Characteristics of Solids Liquid State of Matter: Characteristics of Liquids Gaseous State of Matter: Characteristics of Gases Molar Mass, Worked Examples and Differences with Molecular Mass Elements: Characteristics of Elements Salts and Types of Salt in Chemistry Mixtures and Separation of Mixtures Mixtures and Separation of Mixtures - part 2 Mixtures and Separation of Mixtures - part 3 Physical Change and Chemical Change Concept of Ions and Electrolytes Grahams Law of diffusion, Worked Example and Importance


Academic Questions in Chemistry

Please check out our Test Your Knowledge page to see all Questions and Answers

Which of the following is NOT a characteristic of chemical change?

  • A. A new thing is formed
  • B. It cannot be easily separated into it's constituents elements
  • C. A new chemical formula accompanies whatever is formed
  • D. The burning of candle is an example of a chemical change
  • E. Blood is an example of a chemical change
  • F. Iron rust is an example of a chemical change

Which of the following statement is FALSE concerning a physical change _____.

  • A. Substances formed in a physical change have a unique chemical formula and IUPAC name
  • B. It's a change that is easily reversible
  • C. It's a change that can be separated via an appropriate separation technique
  • D. No new substance is formed
  • E. A mixture of salt and water is a physical change
  • F. Physical change can result to a change in color and shapes of substances

The following substances will sublime EXCEPT _____.

  • A. Sodium Cryolite
  • B. Solid Carbon(IV)oxide
  • C. Arsenic
  • D. Sulphur
  • E. Iodine Crystals
  • F. Naphthalene

Which of the following is a state of matter?

  • A. Ions
  • B. Plasma
  • C. Compounds
  • D. Molecules
  • E. Atoms
  • F. None of the above

The ideal way of separating a mixture of blood is through _____.

  • A. Chromatography
  • B. Fractional Distillation
  • C. Centrifugation
  • D. Filtration
  • E. Separating Funnel
  • F. Fractional Crystallization

Which of the following separation technique is used to separate an insoluble solid that sediments in a liquid?

  • A. Crystallization
  • B. Fractional Crystallization
  • C. Sublimation
  • D. Separating Funnel
  • E. Fractional Distillation
  • F. Decantation

A _____ mixture is said to be uniform all through.

  • A. Homogenic
  • B. Heterogenic
  • C. Homogenous
  • D. Heterogenous
  • E. Concentrated
  • F. Diluted

The reaction involving an acid and a base is termed _____.

  • A. Hydrolysis
  • B. Neutralization
  • C. Combustion
  • D. Displacement
  • E. Decomposition
  • F. Sublimation

Separation of Mixtures:

Recall that a mixture is made up of two or more substances physically combined.

Please read more on Elements, Compounds and Mixtures here.

In this article we will continue from where we previously stopped. In case you wish to read the Part one of this topic; it's present 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.

Note: 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.

Please read on the Red Blood Cells here.

Below is an image of separated blood components via the process of centrifugation.

Centrifugation - Len Academy

Using the above diagram as a reference, 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 sedimented.
  • The upper layer containing the plasma will be seen above it.

Next, the plasma can then be carefully decanted from the test tube. (Please see sedimentation and decantation in the part 1 of this article).

Types of Centrifugation

Below are some of the types of centrifugation:

  • Differential Pelleting or Differential Centrifugation
  • Isopynic Centrifugation
  • Density Gradient Centrifugation
  • Rate-Zonal Density-Gradient Centrifugation

 

(6) Sublimation

Matter exists in 4 states. These are:

On heating a solid, it changes to liquid. If we continue heating, the liquid will eventually change 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 can be defined as a process whereby a heated solid changes directly to gas without passing through the liquid phase.

A sublimate is a substance that changes directly from solid to gas or from gas to solid.

Such solids are said to sublime.

The diagram below shows sublimation via a solid that sublimes. (Ammonium Chloride or NH4Cl):

Sublimation - Len Academy

Examples of solids that sublime are:

  • Ammonium Chloride (NH4Cl)
  • Iodine Crystals
  • Sulphur
  • Solid Carbon(IV)oxide (CO2) or Dry Ice
  • Arsenic
  • Naphthalene

Sublimation is used to separate two salts (or solids) in which one sublimes and the other does not.

An an instance, a mixture of common salt (NaCl) and iodine crystals (I) can be separated via sublimation.

On heating, NaCl remains in the heated dish or container while the iodine crystals sublimes; (that is; it changes into a gas and may be collected afterwards as the sublimate).

Please read on Salts and Types of Salt here.

 

(7) Distillation

Distillation is a technique used to separate two or more miscible liquid that have different boiling points.

Note: The boiling points of the different liquids are not usually at a close range.

Think of miscible liquids as two or more liquids that can dissolve in each other (or one another).

The mixture of water and ethanol is a typical example of a mixture that can be separated via distillation. This is so because they are both miscible and have different boiling points.

The mixture of water and acetone are also miscible and can be separated via distillation.

  • Water boils at 100oC
  • Ethanol boils at 78oC

The image below shows the separation of water and ethanol via distillation:

Distillation - Len Academy

Steps involved in Distillation

  1. To carry out distillation, the mixtures of both liquids are heated in a tube until the one with a lower boiling point (ethanol in our instance) vapourizes or changes to vapour at 78oC.
    Please read on the Concept of Heat and Temperature here.
  2. The vapour is collected and cooled by passing it through a condenser.
  3. The condenser compresses the vapour (gaseous ethanol) into liquid.
    Please read on the Parts of a Refrigerator and how they Operate here.
  4. The ethanol is collected; and is referred to as the distillate.
  5. The water remains in the heated tube since its boiling point is 100oC.

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:

  • Separate a Solid and a Liquid: The evaporated liquid is collected and condensed while the solid remains in the container.
  • Purify Liquid: This is true since only the pure liquid will vapourize leaving behind the solid impurities in the container.

Please read on the Separation of Mixtures - Part 3 here.

THANKS FOR READING - Please Help Share!


len

Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.


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Amazing facts in Chemistry

The only letters that failed to appear on the periodic table are letters:

J     &     Q

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


NOTABLE POINTS IN Chemistry

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