Is Matter Around Us Pure
Matter around us is of two types
1. Pure substances
2. Impure substances (mixture)
Pure substance
A material which contains only one kind of atoms or molecules is called pure
substance.
A pure substance is of two types :-
1. Elements
2. Compounds
Elements :- Secure systems which is made up of only one kind of atoms
is called and elements.
Compounds :- A pure substance which is made up of only one kind of
molecules is called compound.
• All elements and compounds are pure substances.
Note :- A pure substance is uniform or homogeneous throughout because
it consists of only one kind of particles this particles are similar to one
another and cannot be separated into simpler particle by any physical process.
Impure substance (mixture)
A mixture is a material which consist two or more different kinds of particles
which do not react chemically but are physically mixed together in any
proportion.
• Mixture are impure substances.
• The pure substance present in the mixture is called components or
constituents.
• Amisha have variable composition therefore no definite formula can be given
to a mixture.
• A mixture does not have a fixed melting point or fixed boiling point.
Elements :- The simplest form or the basic form of a pure substance
which can neither be broken into nor built up from simpler substances by any
physical or chemical method.
Modern definition :- A pure substance that contains only one kind of atoms.
Or
An element is made up of only one kind of atom which are identical in all
respects size, mass, composition etc.
• Robert Boyle was the first scientist who used the term element in 1661.
• Lavoisier was a French chemist who first gave the useful definition of
element.
Elements are found to exist in all the three state of matter.
1. Solid elements :- sodium, iron, silver, zinc, gold, etc.
2. Liquid state :- Mercury, gallium, caesium
3. Gaseous state :- oxygen, hydrogen, nitrogen, helium etc
Classification of element based on physical and chemical properties.
On the basis of physical properties elements have been divided into following
three types :-
1. Metal
2. Non metal
3. Metalloids
Physical properties of metal
1. Metals are malleable :- This means that metals can be hammered or bitten to
form thin sheets without breaking.
2. Metals are ductile :- This means that metals can be drawn or stretched into
thin wire.
Example :- Gold is so ductile that one gram of it can be drawn to form a wire
of about 2 kilometre of length.
3. Metals are good conductor of heat and electricity.
4. Metals are lustrous.
5. Metals are sonorous
6. Metals are generally hard
7. Metals have high tensile strength :- Metals have a high tensile strength
this means that metals can hold large weights without breaking.
8. Metals are solid at room temperature except Mercury.
9. Metals generally have high melting point and boiling point.
10. Metals generally have high density.
Physical properties of nonmetal
1. Non metals are not malleable.
3. Non metals are not ductile.
4. Non metals are bad conductor of electricity and heat except graphite which
is the conductor of electricity and diamond which allow heat to flow from it.
5. Non metals are dull
6. Non metals do not produce sonorous sound.
7. Non metals are generally soft.
8. Non metals have low tensile strength
9. Non metals are generally liquid or in gaseous state at room
temperature.
10. Non metals generally have low density.
Metalloids :- Metals which have properties in between those of metals
and nonmetals are called metalloids or semi-metals.
Example :- silicon, germanium, arsenic, antimony, calurium
Mixture
A mixture is a material which consists of two or more pure substances
(element or compounds) which are not chemically combined but are physically
mixed in any proportion.
Types of mixture
Depending upon the nature of components that are mixed to form mixture,
mixtures have been classified into two categories :-
1. Homogeneous mixture
2. Heterogeneous mixture
Homogeneous mixture :- It is the mixture that has the uniform
distribution of constituent parts is known as homogeneous mixture.
• All homogeneous mixture are solution.
Heterogeneous mixture :- A mixture is said to be heterogeneous if all
the component of the mixture are not truly mixed and there are visible
boundaries of separation between them.
Example :- A mixture of sugar and sand
Iodine
salt (NaCl + KI)
Properties of mixture
• A mixture may be homogeneous or heterogeneous.
• The composition of mixture is variable.
• A mixture does not have a definite melting and boiling point
• Energy is neither absorbed not evolved during the formation of a mixture.
• The properties of a mixture are the properties of its component
• The constituents of a mixture can be separated by simple physical method
such as filteration, evaporation, sublimation, distillation etc.
Compound
A pure substance made up of two or more elements chemically combined together
in a fixed proportion by mass.
E.g. Water (H2O), Common salt (NaCl)
Properties of compound
• A compound is always made up of the same element combined together in fixed
proportion by mass.
E.g. H2O By mass H:O = 1 : 8
• A chemical compound is formed as a result of chemical change and its
properties is different from its constituents.
Fe + S → FeS
• A compound cannot be separated into its constituents by simple physical
method.
• A compound has a definite molecular formula and fixed melting point and
boiling point.
• energy in form of heat and light is usually evolved or observed when a
compound is formed.
• A compound is a homogeneous substance.
Physical and chemical change
The changes taking place around up into following two types :-
1. Physical changes
2. Chemical changes
Physical changes
Those change in which only the physical properties of the substance change
but no new superstars are formed are called physical change.
Example :- melting of ice to form water and freezing of water to form ice.
2. Chemical change
Those change in which news substances are formed are called chemical
change.
Example :- Burning of magnesium ribbon
Burning
of piece of paper
Rusting
of iron
Note :-
• Physical change are temporary and hence can be easily reversed.
• Chemical change are permanent and hence are irreversible.
Solution
Homogeneous mixture of two or more chemically non reacting substances
whose composition can be varied with in limits.
For binary solution there are two constituents.
1. Salute :- the component of the solution which is present in relatively
small proportions.
2. Solvent :- the component of the solution
(a) which is present in relatively large proportion in the solution
(b) whose physical state is the same as that of the resulting solution.
Types of solution
1. Dilute solution :- The solution in which quantity of solute in a
given mass of solvent is very small is called dilute solution.
2. Concentrated solution :- The solution in which quantity of
solute in a given mass of solvent is very large is called concentrated
solution.
3. Saturated solution :- If a solution contains dissolved salute
equal to its solubility then it is called saturated solution.
4. Unsaturated solution :- A solution in which amount of solute
dissolved is less than its solubility at the temperature and more solute
can be dissolved in it is called unsaturated solution.
5. Supersaturated solution :- Sometimes it is also possible to
dissolve more solute than its solubility such solution are known as
supersaturated solution.
Depending upon the size of the solute particles in solution
1 . True solution :- A solution in which the particles of the
solute are broken down to such a fine state that they cannot be seen under
powerful microscope is called a true solution.
Properties of true solution
• A true solution is always clear and transparent or light can easily pass
through it without scattering
• The particles of solute breakdown to almost molecular size and their
diameter is of the order of 1 nm or less.
1nm = 10⁹m
• A true solution can completely passed through filter paper as particle
size of solute is far smaller than the size of pores of filter paper.
• A true solution is homogeneous in nature.
• In a true solution the particles of solute do not settle down, provided
temperature is constant.
• From a true solution the solute can easily be recovered by evaporation
and crystallization.
Types of true solution
Depending upon the physical state of the solute and solvent following
combinations are possible for true solution.
| Solute | Solvent | Solution | Example |
| Solid | Solid | Solid | Alloys |
| Liquid | Solid | Solid | Hg in Ag |
| Gas | Solid | Solid | H gas in palladium |
| Solute | Solvent | Solution | Example |
| Solid | Liquid | Liquid | Sugar in water |
| Liquid | Liquid | Liquid | Petrol in kerosene |
| Gas | Liquid | Liquid | Soft drink |
| Solute | Solvent | Solution | Example |
| Solid | Gas | Gas | Smoke |
| Liquid | Gas | Gas | Fog |
| Gas | Gas | Gas | Air |
Solubility :- The maximum amount of solute that dissolves in a
given amount of solvent at a specific temperature.
Factors that affecting solubility
1. Effect of temperature :-
• Most solids and liquids are more soluble in water at high temperature.
• Gases become less soluble as the temperature increases because the
temperature increases the water tends to fizz somewhat or the dissolved
gas are expelled.
2. Effect of pressure :-
• The solubility of gas increases as the pressure increases.
3. Nature of solvent :-
• solvent with high value of dielectric constant can dissolved polar and
ionic compounds to a large extent than the solvent with low value of
dielectric constant.
4. Nature of solute :-
• Ionic compounds are more soluble in water.
• non-polar compounds are more soluble in non-polar solvent.
5. Size of solute particles :-
• Smaller the size of the particle, greater is the solubility.
Concentration of solution
The amount of solute present in a given amount of solution or the amount
of solute present in a given mass and volume of a solution.
Parameters for measuring concentration of solution
Mass percentage :- the mass of the solute in grams per 100 gram of the
solution is called mass percentage or percentage by weight.
Volume percentage aur percentage by volume :- The volume of solute in ml
present in 100 ml of solution.
Molarity (M) :- the number of moles of solute per litre of solution.
• SI unit is moles/litre.
Molality(m) :- the number of moles of the solute dissolved in 100 gram of
solvent.
• SI unit is mole/kg
Mole fraction (X)
The ratio of the number of the mole of one component to the total number
of moles of all the components present in the solutions.
Let there are three component in a solution A,B and C.
number of moles = nA, nB and nC
Suspension :-
A hetrogenious mixture in which a solid particles are spread throughout
the liquid without dissolving in it.
• They settle as the precipitate, if the suspension is left undisturbed
for sometime.
Properties of suspension
• Suspension is of heterogeneous in nature.
• The particle size in a suspension is more than 100nm.
• The particles in suspension can be seen with naked eyes and also under a
microscope.
• The solid particles present in the suspension can be easily separated by
ordinary filter papers.
• The particles in suspension are unstable.
Colloidal solution :- A colloid is a mixture that is actually
heterogeneous but appears to be homogeneous as the particles are uniformly
spread throughout the solution.
Example :- milk, shaving cream, cheese etc.
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Properties of colloidal solution
• A colloidal solution appears to homogeneous but actually it is
heterogeneous.
• The size of particles of a colloid is bigger than those of a true
solution but smaller than those of suspension.
• Colloidal particle are too small to be individually seen by naked eyes.
• It's particle can pass through filter paper therefore a colloidal cannot
be separated by filtration however they gets separated by a special
technique called centrifugation.
• The colloid are quite stable, particles does not settle down when a
colloidal is left and undisturbed.
• Colloidal particles are big enough to scatter the beam of light passing
through their solution and make it's path visible.
Dispersed phase + dispersed medium = colloidal system
1. Classification of colloidal based on the physical state of the
dispersed phase and dispersed medium.
| Type | Dispersed Phase | Dispersed medium | Example |
| Foam | Gas | Liquid | Soap solution |
| Solid Foam | Gas | Solid | Punic stone |
| Liquid aerosol | Liquid | Gas | Mist, fog |
| Emulsion | Liquid | Liquid | Cream , milk |
| Gel | Liquid | Solid | Butters, cheez, Jam |
| Smoke | Solid | Gas | Dust, Storm |
| Sol | Solid | Liquid | Protein , starch |
| Solid sol | Solid | Solid | alloy |
2. classification based on the nature of interaction between dispersed
phase and dispersed medium.
1. Lyophilic colloids :- In this type of colloids, the dispersed phase has
great attraction for the dispersion medium.
• In such collides, the dispersed phase does not precipitate easily and
the solution are quite stable.
2. Lyophobic colloids :- In this type of colloidal solution, the dispersed
phase has little affinities for the dispersion medium.
• These colloids are easily precipitated on the addition of a small amount
of electrolytes, by heating or by shaking.
• Once precipitated, it is not easy to reconstituted the solution by
simple mixing with the dispersion medium, hence these solutions are called
irreversible solution.
3. classification of colloids based on the types of particles of the
dispersed phase :-
1. Multimolecular colloids
2. Macromolecular colloids
3. Associated colloids
1. Multimolecular colloids :- in this type of colloids, the colloidal
particles are aggregate of atoms or small molecules with the molecular
size less than 1nm.
• In molecules in the aggregate are held together by wonderwall forces.
• they have usually lyophilic character.
2. Macromolecular colloids :- these are the substances having big size
molecule which on dissolution form solution in which the dispersed phase
particle have size in the colloidal range such substances are called
macromolecular colloids.
• This micromolecules forming the dispersed phase are generally polymers
having very high molecular masses.
• They have usually lyophobic character
3. Associated colloids :- certain substances behave as a strong
electrolytes at low concentrations but at higher concentration these
substances exhibits colloidal.
characteristics due to the formation of aggregated particles, these
aggregated particles are called micelles.
• Micelles are called associated colloid
• Kraft temperature :- the formation of micelles take place only above a
particular temperature called Kraft temperature and ever particular
concentration called critical micelles concentration(cmc).
• micelles have both a lyophilic and lyophobic paath.
Special properties of colloids :-
• Colligative property :- like true solution, colloidal solution also
exhibit colligative property such osmotic pressure, elevation in boiling
point, lowering in vapour pressure.
• since colligative properties of a solution depends upon the number of
particles present in solution as well as on their weight.
• Brownian movement :- English Botanist Robert brown noticed that
irregular motion of particle suspended in water. this was letter on named
as Brownian motion.
• when a colloidal solution is viewed through a powerful microscope the
colloidal particles can be seen moving in a random jig-jag paath. This
motion is called Brownian movement. The random motion is due to the
collision between the colloidal particles.
Example :- when a beam of light passes through a dark room the dust
particles can be seen moving in rapid, random fashion.
Electrophoresis :-
Colloidal particles moves toward the oppositely charged electrode when an
external electric field is applied. This phenomenon is called
electrophoresis.
• On applying direct current colloidal particles move and cogulat.
Tyndall effect :-
• All colloidal solution are capable of scattering light.
Tyndall effect :- When a beam of converging rays falls in colloidal
solution a scattering of light by solution particles in all the direction,
gives rise to a bright glowing cone when looked at its side wise. This is
known as tyndall effect.
Example :- Blue colour of sky and sea water
Visibility of tails of comets
Twinkling of stars
Visibility of projector path
Method of separation of the constituents of the mixture :-
1. Decantation and sedimentation :-
This separation technique is applicable for a mixture containing liquid
and other solid component.
• The solid component should be heavier and insoluble in liquid.
Sedimentation :- the process by which insoluble heavy particles in a
liquid are allowed to settle down.
Decantation :- The process by which clear liquid is obtained after
sedimentation is transferred into another container, without disturbing
the settled particles.
2. Filteration :-
This technique is used when a mixture contains two components, of which
only one is soluble in a particular solvent.
• the soluble component passes through the filter paper as filtrate and
the insoluble solid component is retained on the filter paper called
residue.
3. Evaporation :- this technique is applied for the separation of non
volatile Salt from its mixture in volatile liquid.
• On heating the volatile liquid evaporate, leaving behind the soluble
salt.
4. Sublimation :- this process is used to separate a mixture containing
two components one of which can form a sublimate (direct change of solid
to vapour state on heating), while the other do not.
5. Gravity separation :- this technique is used for the separation of a
mixture having component differ in densities.
• The powdered mixture is treated with a stream of running water when the
lighter component are passed away leaving the heavier ones.
6. Magnetic separation :- this method is applied to separate a mixture
containing one magnetic component and the other non magnetic component.
Example :- separation of iron from sand
Powdered iron from sulphur
7. Separating funnel :- this technique is based upon the principle that
when a mixture of two in miscible liquids is allowed to a stand they
separate out in two separate layers depending upon their densities.
8. Chromatography :-
• This method was first discovered by Tswett a rushian botanist in 1906.
• this technique was first used for separation of coloured substance and
hence the name chromatography was given.
• the word chromatography comes from Greek word kroma and graphy, which
means colour and writing.
Types of chromatography :-
Paper chromatography,
Column chromatography,
Thin layer chromatography,
Gas-liquid chromatography,
High performance liquid chromatography, etc.
Paper chromatography :-
Theory
separation of different components of a mixture by paper chromatography is
based upon their different solubility in same solvent.
Procedure :- take a thin strip of a special type of filter paper called
the chromatography filter paper.
Using a pencil, draw a line across the width of the filter paper at about
3 cm from bottom.put a small drop of ink from a sketch pen or a fountain
pen at the centre of this line and let it dry.
As water rises up the paper by capillary action and flows over the spot.
Usually ink is a mixture of two or more coloured dies. the coloured
component which is more soluble in water rises faster and produces the
coloured spot on the paper at higher position.the less soluble component
rise slower and produce colour spot at lower heights.
9. Distillation :- the process of heating a liquid to form vapour and then
cooling the vapour to get back liquid.
Distillate :- the liquid obtained by condensing the vapour is called
distillate.
10. Fractional distillation :-
if the boiling point of two miscible liquids of the mixture are very
closer to one another that means less than 25K or so, the separation
cannot be achieved by simple distillation method. this is due to the
reason that at the boiling point of the more volatile liquid of the
mixture there will be sufficient vapour of the less volatile liquid as
well as a result, both the liquid of the mixture will be distilled
together and The separation cannot achieved.
Gas-liquid solution :-
The gases are usually soluble in water as well as in other solvent to a
certain extent.
The solubility of a gas in liquid depends on
1. Nature of the gas
2. The pressure applied
3. The temperature
4. The nature of the liquid solvent
Henry's law :-
The mass of a gas dissolved in a given volume of a liquid at constant
temperature is directly proportional to the pressure of the gas in
equilibrium with the liquid this is known as Henry's law.
If "m" be the mass of a gas dissolved per unit volume of a solvent at
pressure "p".
Then,
m ∝ p
m = kp
k = Proportionality constant
In terms of mole fraction
x ∝ p
x = KHp
KH = Henry constant
p = partial pressure
x = mole fraction
Application of Henry's law :-
• bottler use the effect of pressure of solubility in producing carbonate
beverages such as champagne and soft drinks. These are bottled under a
pressure slightly greater than 1 atm.
• when the bottles are opened in air the partial pressure of co2 above the
solution decreases and CO2 bubbles out from the solution.
• the exchange of O2/CO2 at cellular level and in lungs is based on
Henry's law.
• in the breathing mixture for deep sea divers, N2 is replaced by less
soluble He, to minimise painful effect.
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