SEPARATION TECHNIQUES

 

SEPARATION TECHNIQUES

    A mixture contains two or more different substances physically combined together.

   Each constituent in a particular mixture still retains its individual properties, i.e, the properties of each substance in a particular mixture is still the same as when it wasn't mixed up with any other Substance.
    Due to the physical properties of substances in a mixture,a mixture can be separated into its components by physical technques or methods,Using the physical properties of its constituents.

TYPES OF SEPARATION TECHNIQUES.

1) SIEVING:

Used to separate solid particles of different sizes.

   A material called mesh,is used to separate the smaller particles from the bigger ones.
    Industries such as mining and garri industries,make use of this method.

2) MAGNETIC SEPARATION

       This is used to separate magnetic substances from non-magnetic ones.

   It is used in steel industry and to remove magnetic impurities from tin-ore.

3) SUBLIMATION.

    Some solids like ammonium chloride and iodine,when heated,sublimes, i.e,they change directly from solid to gaseous state, without Changing first to liquid.
   These types of solids can be separated from other solids of by sublimation because of  their sublimation property  and are purified industrially by the same method.

Sublimation

4. DECANTATION.

    This is used to separate a mixture of a liquid and solid particles that cannot mix together (They seperate into two distinct layers on standing).

 For example,garri and water.  The liquid is poured out or decanted to separate it from the garri but this method is  inaccurate in seperating mixtures.

Decantation

5) FILTRATION

     This is used to separate insoluble particles ( particles that cannot dissolve in liquids) from liquids.

   It is used in industries such as breweries and in purifying water.

   A pourous material is usually used.

Seperation by filtration.

CENTRIFUGATION.

          This  is used to separate  the components of a suspension.  A mach- ine called centrifuge is   used to spin test tubes containing suspensions at high speeds which causes the heavier solid particles in the suspension to go to the buttom of   the test tube,  while the liquid in the test tubes  seperates as an upper layer which can then be poured   out.
   Centrifugation is used for only a small amount of mixture. For example, in hospitals,blood cells are seperated from the plasma by centrifugation.

A Centrifuge.

7) FLOATATION.

   Used in seperating metals from their ores.

8) EVAPORATION TO DRYNESS.

  This is used to recover a solid(the solute) from a solution. In this case,the solvent is lost. This is done using a heated water-bath.

( Solute + solvent =Solution.)

The process of  obtaining Salt from its solution by evaporation.

  Evaporation is the process by which liquid changes to vapour.
 It takes place at all temperatures.
  This process is used in salt-making industries.

9)CRYSTALLIZATION

    This is used in seperating salts that decompose easily when heated,from their solutions.

   The salt produced this way are pure and usually contain water of crystallization.
   It involves heating the salt solution first to make it saturated.When the saturated salt solution cools off,the salt crystals begin to form.

Crystallization.

10) Fractional crystallization.

    When there are two or more solid solute particles in a solution in roughly equal amount,fractional crystallization is used to separate the needed substance (s) from the solution, using the solubility of the different solutes in the solvent.

   The solubility of these solutes must be different, i.e,the temperature at which a solute dissolves must be different from the one at which the other solutes dissolves in the given solvent.

   At a particular temperature, crystals of the relevant solute comes out of the solution(after they had dissolved), leaving the others which are still within their limits of solubility.


 

11) Precipitation.

    When we have a solid,which has different solubilities (rate at which it dissolves),in two different liquids that can mix together,such as water and ethanol.
Precipitation process is used to separate the solid from the liquids.The solid usually dissolve in one of the liquids.
    Forexample,Iron(II)tetraoxosulphate(VI) is soluble (dissolves) in water but not in ethanol (which can mix with water).
     If ethanol is added to a solution of iron(II) tetraoxosulphate (VI) in water,the solid will be precipitated out of the solution and can be seperated by filtering the liquids from it.

12) Distillation.

    This is used to recover a solvent from a solution.

      When we have two liquids in a solution,and they can mix together,and boils at widely different temperatures, distillation can also be used to recover the liquid needed or solvent from the solution.

   The solution is heated in a flask to vapourize the liquid or solvent (called
 EVAPORATION).   The vapour of the solvent or liquid that boils faster(using a thermometer to detect the boiling point) in  order to  vapourize travels alonga condenser called  the liebig  condenser, which  is cooled by the circulating  water  in the outer jacket of the condenser.

   This cooling effect changes the vapour back to liquid,called the distillate,which is then collected in a receiver.
  The solute and other impurities are left behind in the flask.

Distillation.

     Distillation is used in gin and water distilleries for the production of gin and distilled water respectively.

13) Fractional   Distillation.

 

 This is used to separate a mixture of two or more miscible liquids that has little difference in their boiling points. i.e,the boiling point of one liquid is not far from that of the other in the mixture.

    The fractions of liquids distil over in ascending order of their boiling points, starting with the liquid with the lowest boiling point and for this process to be efficient,the difference in boiling point must be more than 10°C.

  The apparatus used are a fractionating column, liebig condenser,retort stand,tripod stand,round and flat buttom flasks,and thermometer.

Fractional Distillation.

    Crude oil is seperated into it's fractions such as petrol,kerosine, Diesel,bitumen,etc,by fractional distillation.

14) seperating funnel method.

   This is used to separate two or more liquids that cannot mix together.The liquids seperates into two or more distinct layers when added together.

   A seperating funnel is used in which the denser liquid layer below is tapped off,while the less dense liquid layer below remains in the funnel.

Seperating funnel method

15) chromatography.

   This is used to separate a mixture such as ink,dye,and amino-acids,etc, into its components through a porous,absorbent medium like paper .

   There are various methods of chromatography such as:

a) Ascending  Paper    chromatograpy

b) Gas Chromatography

c)Thin-layer chromatography

 Chromatography is used in scientific research to identify and analyse substances and in petroleum industries to identify the various components of the fractions such as kerosene and Diesel,obtained from the Distillation of crude oil.

Paper chromatography

   It is used to determine the presence of certain substances in urine and blood of patients to help doctors in their diagnosis.
It is also used to check the components of chemical products.
A substance can be purified using the appropriate seperation techniques.

 TESTS FOR PURITY

   The following are the criteria to determine the purity of a substance:

1) The melting(for a solid) or boiling point (for a liquid) of a substance is always constant at a specific temperature,if impurities are present in the substance,the specific temperature is affected,it changes.
  If the temperature wasn't affected,then the substance is probably pure.

   Impurities increases the boiling point of a substance while it decreases the melting point of a substance. That is,if a liquid or solid is not pure,it will boil at a range of temperatures above or higher than the boiling point of the liquid or melt at a temperature below or lower than the melting point of the solid.

This is applied in countries with low temperature conditions below 0°C to melt the ice on their roads faster by sprinkling salt which serves as an impurity in the ice,hence lowering its melting point so it could melt faster.

2) On a paper chromatogram,a pure substance will give only one stop.

See NATURE OF MATTER

INTRODUCTION TO CHEMISTRY

INTRODUCTION 

TO CHEMISTRY.

Anything that is known to have mass and occupies space is called MATTER. This means everything around us is matter,which can either be SOLID, LIQUID or GAS(the physical states of matter).

The scientific study of the structure, composition, properties, the reactive characteristics and uses of matter is called chemistry.

   

   The reactive characteristics of matter is the ways in which different forms of matter combine with each other.

We study chemistry in order to understand the world around us,thus chemistry is the study of everything around us.

Through the process of science,a study is conducted on a particular matter, series of observations are made about such matter which may have a pattern and this often lead to a problem to be solved.

A reasonable or proposed explanation or an "educated guess" called HYPOTHESIS,is put forward to explain the observations made earlier.This hypothesis can change as it is not yet tested to be true.

 When experiments are made to test the hypothesis,and is found to be correct based on a body of facts that have been repeatedly confirmed through observations and experiments,within the limits of available evidence,the hypothesis becomes a THEORY. 

A Scientific theory is a comprehensive explanation of an important part of nature supported by facts gathered over time and repeatedly confirmed through observations and experiments.Theories are no longer guesses but reliable accounts of the real world.They are proven explanations on observations about something.

  A SCIENTIFIC LAW or PRINCIPLE is then established when the theory has been extensively tested and proven to be true without any exception.

A Scientific law refers to rules for how a particular aspect of nature will behave under certain conditions.This is mostly written as an equation.

The difference between a Scientific theory and a scientific law is that theories explains the reasons for our observations while laws describes what happens.

If the experiments does not support the hypothesis,it is either modified or a new one is produced.

  

This process of studying a problem in science is called the    

SCIENTIFIC METHOD.

{Observations--patterns----problems

----hypothesis

----experiments

----theory

----Law.

USES AND APPLICATION OF CHEMISTRY.

These are some of the various uses of chemistry:

 1) food supply:

 The production of fertilizers such  as urea, calcium,sodium nitrate,etc , pesticides and insecticides has helped to increase the production and protection of food crops from pests greatly.

  

2) Contribution to improved health and sanitation facilities:

through the production of life-saving drugs such as analgesics, antibiotics, tranquilizers, antiseptic, disinfects, anaesthetics and insecticides.

3) clothing:

textile fibres are produced as a result of intensive chemical research.

4)provisions of explosives has helped in military and space science.

5)In building and construction:

Materials such as steel, cement,concrete, bricks, etc,are essential chemical products in building.

6)In transport and communication:

Petrol, diesel or coal are essential chemical products used in transportation.

7) production of nuclear energy 

8) chemistry has helped in the development and growth of industries like glass,cement, paper, textile, leather,dye, petroleum industries,sugar, plastics and pharmaceutical industries,etc.

BAD EFFECTS 

OF CHEMISTRY.

1) pollution by chemical wastes from factories,oil refines and animal life.

2)rusting of iron:this is the slow deterioration from iron to iron(III) oxide in the presence of water and oxygen in air.

3)Drug abuse:drugs like heroin, cocaine and morphine are addictive.

Hope you understand?

See chemical combination

NATURE OF MATTER

THE NATURE OF MATTER

Matter is anything that has mass and occupies space. The mass of an object is the quantity of matter contained in such object. 

 PROPERTIES OF MATTER.

 

1. Physical properties : 

These are the properties of matter associated with physical change.

When a particular aspect of matter undergoes a physical change,no new substances are formed.

Examples of physical properties of matter are boiling and melting point, density, colour, odour,taste, malleability,change of state,etc.

Examples of physical changes are the dissolution of salt in water, freezing of liquid to solid,eg,water to ice,the sublimation of solid to gas,the vaporization of liquid to gas,etc.

2. Chemical properties:

  These are the properties of matter associated with chemical changes.

A chemical change is the one which cannot be easily reversed and in which new substances are formed.

Examples of chemical changes the dissolution of metals and limestone in acid, the rusting of iron, the addition of water to quicklime, the fermentation and decay of substances, etc.

CLASSIFICATIONS OF MATTER.

Matter is basically classified into two groups namely:

 1. Pure substances:

These are substances that has constant chemical composition and properties.

It is further divided into ELEMENTS (metals, non-metals metalloids and Noble gases),

and COMPOUNDS

(Ionic and molecular compounds).

2.Impure substances:

 These are substances formed from the combination of two or more pure substances which could be elements and/ or compounds.

  

Impure substances are also called MIXTURES.

 Mixtures can be homogeneous (solution or colloids) or 

Heterogeneous

(Suspension or colloids).

DEFINITION OF TERMS.

ELEMENTS:

An element is a substance that cannot be separated into simpler units by chemical methods.

There are 118 known elements in the world.

Elements are grouped into:

(a) METALS:

    Metals are elements that ionize by losing electrons to form cations.

examples are calcium,sodium, magnesium, potassium, etc.

PROPERTIES OF   METALS.

1.They are malleable, ductile or sonorous (produces sound)

2.They are lustrous.

3.Good conductors of heat and electricity.

4.High melting and boiling point.

5.High density

6.They have great tensile strength (hardness)

7.They are reducing agents.

8.They form basic oxides when they react with oxygen.examples are Magnesium oxide (MgO), sodium oxide, potassium oxide, etc.

9.They form ionic compounds.

(b) NON-METALS

    Non-metals are elements that ionize by gaining electrons to form negative ions.

examples are chlorine, oxygen, Nitrogen,Iodine,etc.

Properties of non-metals:

 1.They are oxidizing agents.

 

 2.They form acidic oxides when they react with oxygen.eg.

Carbon(iv)oxide, sulphur (vi) oxide,etc.

3.The physical properties of non-metals are the opposite of that of metals, except for the case of melting and boiling point in carbon,a non-metal which has high melting and boiling point like metals.

(C) METALLOIDS.

  These are elements that has intermediate properties between those of metals and non-metals.

  It is also called a SEMI-METAL.

Examples are Antimony,Boron, Silicon,Germanium

Arsenic,and tellurium.etc.

Metalloids tends to be semi- conductors,since they share the properties of metals and non-metals, silicon is a very good example of a semiconductor.

(D)NOBLE GASES.

 These are elements that have low chemical reactivity and are the most stable elements because they have maximum number of valence electrons.

They rarely reacts with other elements because they are already stable.

 They are odourless,colourless and

 can conduct electricity.

Examples of Noble gases are helium, argon,neon, Krypton,xedon,and radon.

COMPOUNDS.

  A compound is a substance which is formed when two or more elements are chemically combined together.

When a compound is formed,it is a new substance with properties entirely different from those of the components elements combined together to form the compound.

For example, the properties of water,a compound which is formed from the combination of Hydrogen and Oxygen,is entirely different from that of Hydrogen and Oxygen.

Examples of compounds are water,sand, caustic soda, Ethanol, sugar,salt, limestone,etc.

MIXTURES.

This is a substance formed by the physical combination of two or more components (elements and/or compounds),which can easily be separated by physical methods.

 

No chemical change is involved in the formation of mixtures and the proportions of each components in a particular mixture varies. 

   TYPES OF MIXTURES.

1.Homogenous mixtures.

  These are mixtures that are uniform in composition throughout any of it's given sample in which the components cannot be distinguished from one another.

 Examples are alloys,salt and water mixture,

Cement,air,powder,milk, bitumen, plastics,blood plasma,wine,wood,etc.

2.Heterogenous mixtures.

  An heterogeneous mixture is a substance in which the components parts can be differentiated from one another,ie,we can easily identify the components that combined together to form it.

Examples are the mixture of sand and water,concrete formed by combining cement and water,sugar and sand mixture, salt and pepper mixture,etc.

DIFFERENCES BETWEEN MIXTURES AND COMPOUNDS.

1.Mixtures can be homogeneous or heterogeneous while compounds are always homogeneous.

2.The constituents in mixtures can easily be separated by physical method because they're not chemically combined while in compounds,the components are chemically combined together and cannot be separated by physical means.

3.The components in a mixture are not fixed in quantity,so they can't be represented by a chemical formula,while in compounds,the quantity of each elements combined together are in fixed ratio to one another,no matter the mass, therefore,a compound can be represented by a chemical formula.

For example,The ratio of Hydrogen to Oxygen in water is always 2:1,in every quantity of water.

4.The properties of a mixture are the sum of those of it's components,while in compounds,the properties of each individual components elements are entirely different from that of the compound formed.

5.No new substance is formed in mixtures but new substances are formed in compounds.

6.Mixtures have variable melting and boiling point while compounds have fixed melting and boiling point.

7.In the formation of mixtures, there's no loss of heat and energy while in compounds, there's loss of heat and energy when they 

are formed.

See kinetic theory of matter ✏️