Notes of Chapter #02 " Three States of matter"

Quality Education At Every level

 Chapter #01 

Introduction of Chemistry 

 Prepared by:

Lecturer. S.Fayyaz Hussain

City Of Knowledge

              (Science Campus)

Add: 24/2 Sheet # 10 Model Colony Near Model Colony Police Station

 Ph # 021-35449369, 0312-5449369

Three states of matter

Introduction:

            Matter is any thing that exists, it is composed of small and tiny particles called atom or molecules. Three states of matter gaseous, liquids and solids easily recognized through their grass properties. For explanation behavior of gases, liquids and solids the basic theory is “Kinetic Theory of Molecules”.

Kinetic Molecular Theory:                             

            This Theory describes the behavior of different stats of matter. However it is a best model for an ideal gas. So, it is also called kinetic molecular theory of gases.

The main postulates of this theory are as given below:   

Postulates:

1)      Gases are composed of a large number of particles that behave like hard, spherical                                                              objects in a state of constant, random motion.

2)      These particles move in a straight line until they collide with another particle or the walls of the container.

3)      These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.

4)      There is no force of attraction between gas particles or between the particles and the walls of the container.

5)      Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.

6)      The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

7)      Gases exert pressure  which the result of collision of molecule of gas to the walls of container    

Behaviors  of gases:       

            The gases have specific  properties by which they are easily distinguished from the liquid & gases. Some of the properties of gases are given below:

1. Diffusibility:

            Diffusibility is an important property of gas. When two or more than gases mix together spontaneously to form a uniform mixture, it is called Diffusibility of gas, and it can be define as,

“The entering of particles of one Gas into the spaces between the Particles of other gases is called Diffusion.”

KMT Explanation:

            According to the kinetic molecular theory, the molecules of a gas are widely separated

and there are large empty spaces due to which they are free to move. Due to this free movement, the molecules of gases mix together and spread out easily.

Example: 

1-                  DIFFUSION of perfume in air.

2-                  Air it self, in which different gases diffuse to each other and form a homogeneous mixture.

2 - COMPRESSIBILITY:

            All the gases are highly compressible. That is, no apply high Pressure, the volume of gas is reduced and the gas is compressed.                                                  

KMT Example:

            According to kinetic molecular theory, the molecules of gas have very large empty spaces between them. When pressured is applied, the molecules come closer and thus the gas is compressed.

Example:
            The pumping of air into a football or a tyre are familiar example of compression of gases.

3- Pressure:

            All the gases exert pressure on the walls of the container in which they are contained, The pressure of the gas is due to the collision of the gas molecule on the walls on a container.

The pressure is define as the force exerted by the gas molecules per unit area, i-e:

 Atmospheric pressure:

            the atmospheric pressure is “the force experienced by any area exposed to Earth’s atmosphere is equal the weight of column of air above it”   

a)      Relationship between atmospheric Pressure  and mm (Hg):  

          One atmosphere pressure is the pressure that supports the column of exactly 760 mm height  of  mercury( Hg) at sea level at 0⁰c   

                              1 atmosphere=760 mm hg.

                             

                                     

                                        1 atmosphere =760 torr.

                                        1 torr =1mm(Hg)

b)         Relationship between the atmospheric pressure  and N/m² or Pascal:

            one atmosphere pressure = 101300 N/m²    = 101300 pa

                                       

            According to second law of motion

Force = mass  x acceleration  

Where  mass = density x  volume

Volume = l x b x h

            Area     = l x b 

           

           

            Where 

                        Density of Mercury                 = 1.35951 x 10⁴ kg/ m³

                        Height of column                    = 0.76 m

                        Acceleration due to gravity    = 9.8 m/s²

UNIT:

i.          PASCALS:

            If force and area are expressed in Newton and (meter)² respectively, then the unit of pressure is called Pascal.

i.e,  =  = Pa

But Newton is kg.m/s².There fore the unit of pressured is also expressed as:

ii.         P.S.I (Pound per Square Inch):

            Another unit of pressure is P.S.I. the atmosphere exerts pressure on our body and it is 14.7 P.S.I.

GAS LAW:        

The gases have volume, pressure, temperature etc. All these quantity are related to one and another according to some statement, called “The gas laws”.. some of the important gas laws are as follow:

ü   Boyle’s law.

ü   Charle’s law.

ü   Avogadro’s law.

ü   Graham’s law of diffusion.

ü   Dalton’s law of partial pressure.

Boyle’s Law:

            Robert Boyle, in 1662, showed the relationship between the pressure and the volume of a gas at constant temperature. This is called “BOYLE’S LAW.”

Statement 1:

            According to the Boyle’s law

“At constant temperature, the volume of a given mass of gas is inversely proportional to the pressure applied on it.”

Explanation:

            It means that the increase in pressure would result in a decrease of volume of a gas, similarly the decrease in pressured result in the increase in the volume.

Simply we can say, if the pressure is doubled, the volume becomes half and if the pressure is reduce to half, the volume becomes double.       

Mathematic Expression:

Mathematically, Boyle’s law can be expressed

 as  (at constant temperature)

ð P x V =K

            Where K = proportionality constant.

This equation gives another statement Boyle’s law, which is as under:

Statement 2:

“At constant temperature, the product of pressure and a volume of a given mass of a gas is always constant.”

Therefore; if

P₁ & V₁ are initial pressure & volume, &

P₂ & V₂ are changed pressure & volume,

Then                            P₁V₁=P₂V₂  This is called “Boyle’s law equation

Graphical Representation:

            When pressure’ P’ of a given mass of a gas is plotted against it’s volume ‘V’, a parabolic curve is obtained, showing the decrease in volume in increasing temperature.  On the contrary, when pressure ‘P’ of a given mass oa a gas is plotted against reciprocal pf volume i.e.  a straight line is obtained. This confirms the direct relationship between ‘P’ and ‘’.

KMT EXPLAINATION:

           

Boyle’s law can easily be explained on the basis of the kinetic theory of gases, when the volume of a given amount of a gas is decrease, there is more crowding of the molecules in that space. This result in more frequent collision between the molecules and the walls of the container and thus the pressure of the gas is increased and vise-versa.

Limitations of Boyle’s law: This law is not obeyed by gases under conditions of high pressure & law temperature.

CHARLE’S LAW:

            In 1787, a French physicist, Charles’s showed the relationship between the volume of a given mass of a gas and it’s temperature at a constant pressure. This law is called Charles’s law

STATEMENT # 1:                         

            According to this law:

“At constant pressure, the volume of a given mass

of a gas is directly proportional to the absolute

                        temperature.”

EXPLAINATION:

            It means, if the pressure is kept constant, the increase in temperature would result also in increase the volume of a given mass of a gas. Similarly, the decrease in temperature results also in decrease in the volume of a gas.

MATHEMATICAL EXPRESSION:

                        Mathematically, Charle’s law can be expressed as:

VaT    (At. Constant Pressure)

OR      V=KT

OR     

This expression gives another statement of Charle’s law, which is as under.

STATEMENT#2:

“At constant pressure, the ratio of volume to the absolute temperature of given mass of a gas is always constant.”

Therefore; if

V₁&T₁ are initial volume & temperature & V₂ &T₂ are changed volume & temperature.

Then

This is called “CHARLES’S law equation.”

EXPERIMENTAL VERIFICATION:

            Consider a gas cylinder fitted with a move able piston. The volume of the gas enclosed in the cylinder is V₁ at temp. T₁ . When the gas is heated to T₂, its volume is increase to V₂ by moving the piston upward. It the pressure on the piston is kept constant, then it is observed that the ratio between V₁ andT₁ is equal to the ratio V₂ and T₂.i.e.           

                                                           

This verifies the Charle’s law.                                    

                                  

                       

    -300 -200         -100      0                 100         200        300

KMT EXPLAINATION:

            This law can be easily explained with the help of Kinetic molecular theory as:

An increase in temperature increases the K.E. of gas molecules which results in their more collision per second against the walls of the container. But if the pressure is kept constant the extra force of the colliding molecules is utilized for the expansion of gas, i.e. increase in volume.

GRAPHICAL REPRESENTATION:

            Charles’s law can also be explained by graphical method, if the volume of the given mass of a gas is plotted against its absolute temperature values at a constant pressure, a straight line is obtained, showing the direct relationship between ‘V’ and ’T’.

If the straight line is extra plotted it intercepts the temperature axis at -273.16^oC. This temperature is called “ABSOLUTE ZERO”.

ABSOLUTE ZERO:

            It is a hypothetical temperature, at which the volume of all gases become zero. Its value is -273.16^oC.This temperature can never be achieved.

The scale on which -273.16^oC is taken as zero is called “KELVIN SCALE” and is indicated by K. Centigrade is related to Kelvin scale as;

^oK = ^oC + 273

AVAGADRO’S LAW:

            In 1811, Amadeo Avagadro stated the relation ship between the volume and the no. of molecules of the gas. This is called “AVAGADRO’S LAW”.

Statement:

            According to Avogadro’s law;“The Volume of a gas is directly proportional to the number of molecules of the gas at constant temperature & pressure”.

Explanation:

            It means that, if we take different sample of different gases at same temperature and pressure, then if the volume of each gas sample is equal, the no. of molecules of each sample will be also equal evidently, if we increase the volume of gas sample, the no, of molecules will be also increase.

            Avogadro’s also found that at the some condition of temperature and pressure, the one mole  of any gas occupies always 22.4dm³ volume, this volume is called molar gas volume. Also, this volume contain always constant no. of particles of gas, and its value is 6.02 x 10²³. This value is called Avagadro’s number.

Mathematical Expression:

            Mathematically, Avogadro’s law can be written as,

V µ n

OR V = K n

Where n= no. of molecules of gas

General Gas Equation:

            Boyle’s law, Charles law and Avogadro’s law may be combined together to give a general relation between the pressure, volume, temperature and no. of moles of a gas. This relationship is called “General Gas Equation”

            According to Boyle’s law

           

            According to Charle’s law

            V µ T

On combining these three laws. We get

OR     

OR      PV= nRT

            This expression is called ‘GENERAL GAS EQUATION’. Where ‘R’ is a proportionally constant and is called gas constant.

For 1mole of a gas, n=1.

\PV=RT

OR     

            When the temperature of a gas changes from T₁ to T₂, then its volume as well as pressure changes from V₁ to V₂ and P₁ to P₂.    

            \ For initial state:

                        & For final state:

Combine these two, we have

            This relationship is used to solve problems regarding changes of volume of gases, due to the changes in the pressure & temperature.

VALUES & UNIT’S OF ‘R’:

(a)                           According to Avagadro’s law, at S.T.P the one mole of any gas occupies a volume of 22.4dm³.

i.e.       T=0˚C=273^oK

            P=1atm.

            n=1mole

            V=22.4dm³

            Then the value and unit of gas constant will be;

(b)                           When ‘P’ is expressed in and volume ‘V’ in m³,then at     S.T.P,

                        P=101300                      V=0.0224m³

                        n=1mole.                                 T=273^oK.

                        Then the value and unit of gas constant will be.

\

R = 8.314 N.m / mole x ^oK

R = 8.314 J/mole x ^oK

GRAHAM’S LAW OF DIFFUSION:

            Diffusion is the natural process by which gases intermix with one another to form a homogenous mixture.

In 1833, Graham established a relation ship between the rate of diffusion of gases and their densities which is terms as “Gaham’s law of diffusion”.

STATEMENT:

            According to this law,

“The rates of diffusion of gases are inversely proportional to the square root of their densities under same condition of temperature and pressure”.

MATHEMATICAL Expression:

            Mathematically, graham’s law can be expressed as:

OR                 

            Where  r = rate of diffusion of gas,

                        d= density of gas,

                        K= Proportionality constant.

            Suppose two gases with densities d₁ & d₂, diffuse into each other. If the rate of diffusion of the gases are r₁ & r­₂ respectively, then according to graham’s law:

            For gas 1,       

&         For gas 2,       

By combining the two equations, we get

            Since the density of a gas is proportional to its molecular mass, so Graham’s law may also be expressed as:

Experimental Verification:

            Take a 100 cm long glass tube. Plug one end of it with a piece of cotton soaked in NH₃ solution and the other with a piece of cotton soaked in HCl solution as shown in the diagram.

            The vapours of NH₃ and HCl escape into the glass tube simultaneously. A white ring of NH₄Cl appears at the meeting point of the two gases. Measure out the distance of te white ring from two ends.

Suppose, the distance covered by NH₃ = 60 cm

& the distance covered by HCl = 40 cm

Since the time ‘t’ is the same, therefore The rate of diffusion of NH₃ gas =

& the rate of diffusion of HCl gas =

\ Molecular Mass of NH₃ = = 17

& Molecular Mass of HCl = = 36.5

\ According to Graham’s law of diffusion,

1.5       =          1.5

Since L.H.S. = R.H.S., therefore Graham’s law of diffusion of gases is verified.

KMT Explanation:

            According to the Kinetic Molecular Theory, the Kinetic energies of the same quantities of gases are the same at the same conditions of temperature and pressure i.e.

K.E₁ = K.E₂

OR     

=>

\ Velocity of gas molecules = Rate of diffusion

\ V = r

\

m₂ = M₂ (Molecular Mass of gas 2)

m₁ = M₁ (Molecular Mass of gas 1)

OR

            This equation shows that the rates of diffusion of gas are inversely proportional to the square roots of their masses.

Hence the Graham’s law is verified.

Dalton’s Law of Partial Pressure:

            The behavior observed, when two or more gases are placed in same container is summarize in Dalton’s Law of Partial Pressure.

Statement:

                        In 1801, Dalton’s found that

            “The total pressure of a gaseous mixture is the sum of the

             partial pressure, exerted by each of the gases present in

                   the mixture”.

Mathematical Expression:

            Mathematically this law can be expressed as,

P = P₁ + P₂ + P₃ + ………………

Where P          = Total pressure of gaseous mixture

                        P₁         = Partial Pressure of gas 1.

                        P₂         = Partial Pressure of gas 2.

                        P₃         = Partial Pressure of gas 3.

Explanation:

            When two or more gases which do not react chemically, are mixed in the same container, then each gas will exert the same pressure as it would exert if it alone occupied the volume containing the mixed gases, under the same condition. This portion of the total pressure of a mixture is known as PARTIAL PRESSURE. Dalton observed that the total pressure of a mixture of different gases is always equal to the sum of individual or partial pressure of each gas present in a mixture.

Experimental Verification:

            Let us suppose that two different gases A & B are confined in two separate compartments as shown, in the figure. Both the compartments are of same size with a pressure measuring device.

Now suppose that the pressure of a gas is ‘A’ is 800 torr and that of gas ‘B’ is 900 torr in their separate compartments. If gas ‘A’ was transferred into the compartment ‘B’ with the help of a movable piston through the total pressure in this compartment would be the sum of the original pressure in the two compartments when the gases were occupying same volume separately.

i.e.       P_total     =          P_A        +          P_B

            1700    =          800      +          900

            1700    =          1700

Hence, law is verified.

KMT Explanation:

            Since there are not attractive or repulsive forces between gases molecules at ordinary temperature and pressure, therefore each gas behaves independent of the pressure of other gases in the mixture.

Each gas exerts a separate pressure on the container because of collision of its molecules with the walls of container. Thus the total pressure in the container is caused by the sum of all the collision.

Ideal Gases:

           

The gas which obeys all the gas laws, of all temperature & pressure and its behavior can be explained on the basis of Kinetic molecular theory, is called “IDEAL GAS”. The ideal gas has the following two significant properties.

a)         The molecules of the ideal gas don’t attract to each other.

b)         The size of the molecules is negligible or they have not space  to occupy.

        In actual practice, there exists no ideal gas in the nature, but the gases like H₂ or He

        show ideal behavior at specific temperature and pressure.

Causes of Deviation:

           

The real gases deviate from ideal behavior due to the following faulty assumptions of the Kinetic Theory.

i)    That, the total volume of the gas particles is negligible as compared to the volume of  the gas itself.

      This may be acceptable at low pressure but at high pressure the molecules are force together, as a result, the volume of a gas decreases while the total volume of its molecules remains unchanged. Thus the total volume of its molecules can not neglect as compared to the volume of gas itself.

ii)  That, there are no attractive or repulsive forces between the gas particles.

      This is also not true at high pressure because when the pressure is increased, the gas molecules become closer and thus attractive forces increases. This attractive force between the molecules is known as Inter-molecular forces. This inter-molecular forces cause the real gas to deviate from ideal behavior.

liquid state

Behaviors of Liquids:

            The liquids show the following behaviors or properties by which they are distinguished from other substances.

1. Diffusibility:

           

            Liquids can diffuse into one another, they mix with each other to form a homogeneous mixture e.g. if a drop of ink is added in water it spreads out in all direction, till a homogenous colour mixture is formed. But the rates of diffusion are much lesser than those of gases, because the liquids molecules have inter molecular attraction and are not free to move like gases.

2. Compressibility:

           

            Unlike gases, liquids are normally incompressible. However, at very high pressure the volume of a liquid is reduced very slightly.

This behavior of liquids is due to the close packing of their molecules. The molecules of liquids are so close to each other that the repulsions of electron clouds resist all attempts at bringing tem further closer.

3. Expansion & Contraction:

           

            Some of the liquids show expansion on heating or they show increase in their volumes. The temperature increases the K.E. of the liquid molecules increase due to this they move apart, causing increase in volume or the liquid show expansion.

            On, the other hand on cooling liquids show decrease in their volumes, i.e. the show contraction. It is due to cooling process, where thermal energy of molecules is removed. This causes decrease in Kinetic energy of the molecules and decreases in inter – spaces, and the liquid is contracted.

Viscosity:

            It is common observation that some liquids flow more readily than the other. For example water moves over a glass plate more quickly than glycerine. Similarly, honey and mobil oil flow more slowly than water. Hence, liquids which flow easily are called “MOBILE” & such liquids which do not flow easily are known as “Viscous”. The resistance of a liquid to flow is expressed in terms of viscosity, which may be defined as,

“The internal resistance to the flow of a liquid is called its viscosity”

Viscosity is represented by ‘h’ and its unit is “POLSE”. Normally smaller units “CENTIPOISE” or “MILLIPOISE” are used.

1 POISE          =          1 gm/cm

& 1 POISE      =          100 CENTIPOISE

                        =          1000 MILLIPOISE

Explanation:

            Imagine a liquid flowing through a tube and consists of concentric layers. The layers

in contact with the walls of the tube remain almost stationary, whereas the layers in the centre have the highest velocity and the intermediate layers move with a gradation of velocities. Hence each layer exerts a drag on the next layer which causes resistance to the flow.

max velocity

	min velocity

The liquid whose layers offer more resistance to its flow is more viscous than the liquids whose layer offer less resistance. Therefore glycerine and honey are more viscous than water, ether & alcohol.

Factors affecting Viscosity:

            On the following factors affect the viscosity of a liquid.

a) Molecular Size:

            Viscosity increases with increase in molecular size, because it is difficult for the layer molecules to slide over another and to go from one layer to the other.

b) Molecular Shape:

            An irregular shape of molecules also causes the molecules to offer more resistance than the molecules of regular shape. Thus the                nonlinear molecules have greater viscosity than linear ones.

c) Inter-Molecular Attraction:

            Greater the inter – molecular attraction in a liquid, greater will be force to resist the flow. Thus the viscosity will also be higher.

d) Temperature:

            Viscosities of the liquids decrease with the increasing the temperature and vice-versa. This is due to the increase of average K.E. of the molecules at higher temperature.

Surface Tension:

            “The inter-molecular force that drawn the molecules on the surface of a liquid together causing the surface to act like a thin elastic skin, this phenomenon is called SURFACE TENSION”.                   

OR

“The force per unit length or energy per unit area of the surface of a liquid is called SURFACE TENSION”.

Surface tension of the liquid is represented by  g    OR   s, and its units are dynes / cm   OR      erg / cm².

Explanation:

           

We consider a molecule ‘A’ at the surface and ‘B’ inside the liquid. The resultant force on ‘B’ is zero, because, it is attracted equally in all direction. On the other hand, molecule ‘A’ is attracted laterally by neighbouring molecules with equal forces. The molecule ‘A’ is also attracted downward at right angle by the molecules underneath it. As there is no liquid on its to balance the downward attractive forces, therefore, therefore the molecules ‘A’ is pulled inside the liquid. A similar pull is also experienced by other molecules on the surface of the liquid. However, the inward movement of these molecules is not possible, because of the lateral forces of neighbouring molecules. This creates a constant tension in the molecules of the surface of the liquid, called “SURFACE TENSION”.

            The surface of liquid thus appears like a stretched membrane. It is so strong that a needle or a shaving blade can float on it.

              

Factors Effecting Surface Tension:

            The surface tension of a liquid depends upon two factors:

a) Inter-Molecular Attraction:

            Stronger the inter-molecular attractive forces, greater is the surface tension, and vise versa. For example, water possesses higher surface tension than most of the organic solvents. This is because of strong inter – molecular forces in water due to hydrogen bonding.

b) Temperature:

            Surface tension of a liquid also depends on temperature, it decreases with the increase of temperature and vise – versa.

Vapours Pressure:

“The Pressure exerted by the vapours of a liquid, in equilibrium state with the pure liquid itself at a given temperature is called VAPOURS PRESSURE” of a liquid”.

Explanation:

Consider a volatile liquid in a closed container. Due to evaporation, the vapours are accumulated in the space above the surface of the liquid. During their motion, vapours lose a part of K.E. and are condensed again. After sometime, the space above the surface of the liquid is saturated with vapours. At this stage the rate of condensation becomes equal to the rate of evaporation. This is called the “Equilibrium State”.

                       

                 Liquid                     Vapours

           

The vapours due to their continuous state of random motion exert pressure on the surface of the liquid. This pressure of vapours at the equilibrium is called “Vapours Pressure”.

Boiling Point:

           

            The vapours pressure of a liquid increases with the increase in its temperature. A certain temperature is reached when the vapours pressure of the liquid becomes equal to the atmospheric pressure. At this temperature, the gas bubbles can be seen coming out of the liquid. It is called the Boiling of the Liquid & the temperature is called Boiling Point, so it can be defined as

“Boiling Point is the temperature at which the vapours pressure of a liquid becomes equal to the atmospheric pressure”.

solid state

Behaviors of Solid:

           

            The solids have the following properties and characteristics due to which they are easily distinguished from liquid and gases.

i. Compressibility:

            The compressibility of solids is nearly zero, because the particles in solid are closely packed and so tightly bound together that no                inter-spaces are left. Hence the density of solids is much higher than gases and liquids.

ii. Deformity:

            Solids are deformed or shattered by higher pressure. This is because, when some particles are dislocated the forces of attraction is so strong that the rearranged atoms are held equally well to their new neighbours.

iii. Diffusibility:

            Diffusion is very slow in solids when compared with liquids and gases. There is no free movement of the particles but there is only vibration about the mean position e.g. Zn & Cu sheets when placed in close contact for a long time, they diffuse into each other in very slight ratio.

iv. Melting:

           

            On heating the solids change to liquid state and they melts.

In terms of Kinetic Theory when solids are heated, vibrational energy of their particles increases; until at melting point, some particles are vibrating with sufficient energy to overcome the forces holding them, hence they become mobile i.e. Solid fuse.

v. Sublimation:

           

            There are some solids substances as camphor iodine, naphthalene etc, which change directly to vapour on heating without passing through liquid phase. This phenomenon is called Sublimation.

In terms of Kinetic Theory, the inter-molecular force in which solids is less ordinary solids, hence high energy molecules at solid surface overcome the attractive forces and directly pass into vapours.

vi. Latent Heat of Fusion:

           

            Latent Heat of fusion is the heat energy which is required to change  1 gram of a solid into liquid at its melting point e.g. 1 gm of ice at 0 ^oC requires 334 J of heat energy to convert ice completely into water. Hence 334 J is called Latent Heat of fusion of ice.

Classification of Solids:

There are two main types of solids which are as follows:

§     Crystalline Solid

§     Amorphous Solid

1. Crystalline Solid:

           

            The solids which have very orderly arrangement of their particles are called “CRYSTALLINE SOLID”. In this type of solid, the particles are arranged in layers and plane. Due to this they have definite geometric shapes e.g. Diamond, Graphite, NaCl etc are crystalline solids.

2. Amorphous Solid:

           

            These are the solids which do not have definite geometrical shape. The particles of such solids have a random i.e. non repetitive three dimensional arrangements. If a substance in liquid state is cooled rapidly, the particles are unable to arrange themselves in an orderly fashion, hence an amorphous solids results. Examples are glass, plastic, rubber etc.

Difference b/w Crystalline & Amorphous Solids

Crystalline Solid	Amorphous Solid
Geometry
Particles of crystalline solids are arranged in an orderly three dimensional network called crystal, hence they have definite shape.	Particles of amorphous solids are not arranged in a definite pattern, hence they do not have a definite shape.
Melting Point
Crystalline solids have sharp melting point, this is because attractive forces between particles long range and uniform.	Amorphous solids melt over a wide range of temperature i.e. they do not have sharp melting point, because the inter-molecular forces vary from place  to place
Cleavage
The breakage of a big crystal into smaller crystals of identical shape is called cleavage. Crystals cleavage along particular direction.	Amorphous solids do not break down at fixed cleavage planes.
Anisotropy & Isotropy
Physical properties of crystals such as electrical conductivity, refractive index, , are different in different direction. This property is called Anisotropy. For Example Graphite can conduct electricity parallel to its plane of layers but not perpendicular to plane.	Amorphous solids are isotropic, i.e. their physical properties are same in directions.
Symmetry
When crystalline solids, are rotated about an axis their appearance does not change i.e. they possess symmetry.	Amorphous solids are not symmetrical.

Types of Crystals:

            Crystals are classified on the basis of kind of bond, by which atoms, ions or molecules are held together in solid. They are classified into the following four types.

1) Ionic Crystals:

            Such crystals which have ionic bonds are called Ionic Crystals. In ionic crystals, there are electrostatic forces of attraction between positive and negative ions.

e.g. NaCl, KCl, BaCl₂­ etc.

Properties:

1. The ionic crystals are brittle.

2. The ionic crystals are bad conductors of electricity.

3. They have high melting point.

4. They have very high values of lattice energy.

5. They have high melting point.

2) Covalent Crystals:

            In covalent crystals the atoms or molecules are held together by covalent bonds. Non – metals usually form this type of crystals e.g. Diamond, Sic etc.

Properties:

1. They are very hard.

2. The covalent crystals have high melting points.

3. They have low coefficients of expansion.

4. They have high refractive indices.

5. They are non – conductors of electricity.

3) Molecular Crystals:

            In molecular crystals, the molecules are held together due to Vander Wall’s forces. Vander Wall’s forces result from dipole-dipole interaction.

e.g. H₂O, CO₂, NH₃ etc.

Properties:

1. Molecular crystals are soft, wax like solids.

2. They have low melting point.

3. They are non-conductor of electricity.

4. They are non-conductor of heat.

5. They are usually brittle.

4) Metallic crystals:

            In metal, valence electrons are loosely attached in a crystal and these electrons can jump to the other atoms. When one or more electrons detach themselves from an atom a positive charge on the atom is produced. Thus, free electrons serve as an atmosphere of evenly distributed negative charge and positive ions are immersed in it. Examples may be taken as Na, Cu or Fe etc.

Properties:

1. The metals are good conductor of heat and electricity.

2. They have high tensile strength.

3. They are malleable and ductile.

4. They have luster.

5. They have high lattice energies.

Isomorphism:

            When two different substances have same crystal structure, they are said to be isomorphous and the phenomenon is called Isomorphism.e.g.

K₂Cr₂O₇ & K₂SO₄ are orthorhombic.

CaCO₃ & NaNO₂ are Trigonal.

ZnSO₄ & NiSO₄ are orthorhombic.

Properties:

            Isomorphic substances have following properties:

1. They have different physical and chemical properties.

2. They have empirical formula.

3. When their solutions are mixed, they from mixed crystals.

4. They show the property of over growth.

Polymorphism:

            The substance which can exist in more than one crystalline form, under different condition, is called Polymorphous and the phenomenon is called Polymorphism. e.g. CaCO₃ exist in nature in two crystalline form

1. Calcite , which is Trigonal      2. Aragonite, which is orthorhombic

UNIT CELL:

            Unit cell is a basic structural of a crystal having a definite geometrical shape and containing a definite no. of atoms or ions. The different arrangement of these unit cells in three dimensions, give different external shape of the crystal.

CRYSTAL SYSTEM:

            These are the group of crystals whose external shapes are built up by only one kind of unit cell. A crystal unit cell is three dimensional therefore it has three axis and three angles b/w three axis. The length, breath and height a, b & c, while angle between these lengths  µ ,b and g.   The crystal are classified into a following even crystal system formed from seven types of unit cell.

1. CUBIC SYSTEM:

            In this system, all length are equal and all the angle are of 90˚. i.e.

a=b=c

& a=b=g=90˚

e.g.                  Nacl, NaBr, Diamond etc.

2-TETRAGONAL SYSTEM:

            In this system, all the length are different but the angles are equal and of 90˚.

i.e.       a=b≠ c

&         µ=b=g=90˚

e.g.      SnO₂, BaSO₄,4H₂O

3-orthorhombic SYSTEM:

            In this system, all the length are different but the angle are equal to 90˚.

i.e.       a ≠ b ≠ c

& µ=b=g=90˚

e.g.      FeSO₄.7H₂O, ZnSO₄.7H₂O etc.

4-TRIGONAL SYSTEM: (RHOMBOHEDRAL)

            In this system, all the length are equal and all the angles are equal but more than 90^o & less than 120^o i.e.

a = b = c

&

µ=b=g¹90˚ (Angles > 90^o < 120^o)

e.g. KNO₃, AgNO₃ etc.

5. Hexagonal System:

            In this systems tow lengths are equal but third length is different. Also, two angles are of 90^o but third angle is 120^o i.e.

a = b ≠ c

& µ=b =90˚

g = 120^o

            e.g.      SiO₂, Graphite etc

6. Mono clinical System:

            In this system, all the lengths are different. Two angles a^’ and g^’ are of 90^o and third angle b^’ is different.

i.e. a ≠ b ≠ c

& a = g = 90^o

b ≠ 90^o

e.g.

CuSO₄.5H₂O, Na₂CO₃.10H₂O

7. Triclinic System:

In this system, all the lengths and all the angles are different.

i.e. a ≠ b ≠ c

a ≠ b ≠ g ≠ 90^o

e.g.

CuSO₄.5H₂O, K₂Cr₂O₇ etc.