Si unit of heat energy

Introduction :

Heat: Heat is a form of energy. It gives the feeling of hotness and establishes its existence .The Sun is the natural source of heat and light. Heat light is required for the process of Photosynthesis. We need heat energy for our daily activities. Heat energy is necessary to heat water, to cook, to manufacture glass, cement, and iron in factories. The food we take provides heat energy to us.
Sun is the natural source of heat.

Abundant heat and light we get from the sun.Solar energy is necessary for all the activities on the earth.Can you tell how rain is formed?Due to heat.

Heat is a Form of Energy and its Units

How can we say that is form energy?Is there any basis for it ?Energy is the ability to do work.Energy can be converted from one from to another.If heat is a from of energy.,it should be able to to do work.It should also be possible to convert heat into other forms of energy.
Since heat is a form of energy,should not the units of heat be the same of energy?The international unit of heat is called joule.Another unit called calorie is also used as the unit of heat.How much heat is a calorie? The amount of heat required to raise the temperature of one gram of water by one degree Celsius is called calorie.

History of Joule

The international unit of heat(any other form of energy) is called joule in honor of the British scientist James pres cot Joule.joule was accepted as the international unit of heat in 1948.
Meaning of calorie:
It is the amount of heat needed to increase the temperature of 1KG of water by 1⁰c.

Laws of motion application

Newton's Laws of Motion - First Law Of Motion
Newton's Laws of Motion - Examples Of The First Law
Newton's Laws of Motion - Second Law Of Motion

The Newton first law of motion concentrates on a state of constant motion but adds unless an outside influence, force, acts on it. Force produces a change in the state of motion (velocity describes a body's motion); that is, an acceleration. Newton found that the greater a body's mass the greater the force required to overcome its inertia and mass is taken as a quantitative measure of a bod…

Newton's Laws of Motion - Applications Of The Second Law

For objects thrown upward, gravitational acceleration is still 32 ft/sec/sec downward. A ball thrown upward with an initial velocity of 80 ft/sec has a velocity after one second of 80-32= 48 ft/sec, after two seconds 48-32= 16 ft/sec, and after three seconds 16-32= -16 ft/sec (now downward), etc. At 2.5 seconds the ball had a zero velocity and after another 2.5 seconds it hits the ground with a ve…

Newton's Laws of Motion - Third Law Of Motion Or Law Of Action-reaction
Newton questioned the interacting force an outside agent exerted on another to change its state of motion. He concluded that this interaction was mutual so that when you exert a force on something you get the feeling the other is exerting a force on you. Newton's third law of motion states: When one body exerts a force on a second body, the second body exerts an equal and opposite force on …

Newton's Laws of Motion - Examples Of The Third Law
(1) What enables us to walk? To move forward parallel to the floor we must push backward on the floor with one foot. By the third law, the floor pushes forward, moving us forward. Then the process is repeated with the other foot, etc. This cannot occur unless there is friction between the foot and floor and on a frictionless surface we would not be able to walk. (2) How can airplanes fly at high a…

Read more: Newton's Laws of Motion - First Law Of Motion, Examples Of The First Law, Second Law Of Motion, Applications Of The Second Law http://science.jrank.org/pages/4658/Newton-s-Laws-Motion.html#ixzz0paAGxF7r

Sir Isaac Newton three Laws of Motion

Introduction :
In 1684, encouraged by his friend Edmund Halley, Sir Isaac Newton embarked on writing what was to be The principia mathematica was one of the greatest scientific works ever published. He enunciated the three laws of motion and the universal law of gravitation, which explained all the three Kepler's laws of planetary motion.
                    
In earlier times, motion of bodies was studied by philosophers. Most philosophers believed that a body moved with uniform velocity due to some external agent. They also thought that if there were no external agent the body would naturally come to rest. Galileo was the first to show that some external force was necessary to change the velocity of a body but that no external force was necessary to maintain the velocity of a body. This principle was adopted by Newton in his first law of motion.

Sir Issac Newton first law:

    The law enables us to define inertia and force. From this law it can be concluded that if the net external force on an object is zero, the acceleration of the object is zero.
Inertia ; If the net external force is zero, a body at rest continues to be at rest and a body in motion continues to move with uniform velocity. This property is called inertia. It is the resistance to change the state of uniform motion. Mass is a measure of inertia.  Ex: when the bus stops suddenly our feet stop due to the friction. But the rest of the body continues to move forward due to inertia of motion.
Force :  It is the physical quantity that changes or tries to change the state of rest or of uniform motion along a straight line.

Sir Issac Newton second law:

By Newton first law of motion, when there is no net external force on a body it moves with uniform velocity. In terms of momentum, the body will have constant momentum when there is no net external force on a body, Hence, when the momentum of a body changes the body must be under the action of a net external force.
           
Newton's second law of motion states that " The rate of change of momentum of a body is directly proportional to the resultant or net external force action on the body and takes place in the direction  in which the force acts" .
            
A body of mass m moving with velocity v is under the action of a net external force F in the direction of velocity. If its velocity is increased by `Deltav` in a time interval `Deltat`  then by the second law
                                                  F `prop` dp /dt             (or)                   F  `prop` d/dt (mv)        (since p = mv)
                               F = k d/dt (mv)                    , Assuming that the mass of the body is constant
                   F = k m dv/dt  =  k m a    , which shows that the net force is proportional to the product of mass and acceleration.
              
The proportional constant k is made equal to one, by properly selecting the unit of force. The SI unit of force is newton which is defined as the force that causes an acceleration for 1 ms^-2 on a body of mass 1 kg. Substituting k = 1 in F = k m a ,  we get
                                                    F  =  m a .
               The dimensional formula of force is [MLT^-2] .

Sir Issac Newton third law:

Newton's third law tells us about the origin of the force that causes acceleration. It states that " to every action, there is always an equal and opposite reaction " .
                     
In this statement, action and reaction are nothing but forces. When we hit a wall we apply  some force on the wall. An equal and opposite force acts on us due to the wall at the same instant of time. When we walk on the road we push the road backward and the road applies an equal and opposite force on us so that we can move forward. Newton's third law is not strictly applicable when the interaction between two bodies separated by a large distance is considered.

Newtons theory

NEWTON'S LOW OFUNIVERSAL GRAVITATION:-
The mechanisms of Newton's law of universal gravitation; a point mass m₁ attracts another point mass m₂ by a force F₂ which is proportional to the product of the two masses and inversely proportional to the square of the distance (r) between them. Regardless of masses or distance, the magnitudes of |F₁| and |F₂| will always be equal. G is the gravitational constant.

Newton's law of universal gravitation states that every massive particle in the universe attracts every other massive particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically-symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.) This is a general physical law derived from empirical observations by what Newton called induction.^[1] It is a part of classical mechanics and was formulated in Newton's work Philosophiae Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him – see History section below.) In modern language, the law states the following:

Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is directly proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses:^[2]

where:

·         F is the magnitude of the gravitational force between the two point masses,

·         G is the gravitational constant,

·         m₁ is the mass of the first point mass,

·         m₂ is the mass of the second point mass, and

·         r is the distance between the two point masses.

Lorentz force

Proof of Faraday's Law
It is evident from Faraday's experiments that whenever there is a change in the magnetic flux passing through a closed circuit, an electric current is induced in the circuit. It can be explained on the basis of Lorentz force.

Suppose a conducting-rod JK (Fig. 7) is being moved without friction on the arms of a U-shaped stationary conductor MNOL with a velocity v towards right. The conductor is situated in a magnetic field B perpendicular to the plane of paper directed downwards. Due to the motion of the conducting-rod, the free electrons present in the rod are acted upon by a magnetic (Lorentz) force F_m of magnitude qvB which takes the electrons from the end J of the rod to the end K. Since a closed circuit is available to the electrons, they drift along the path J-*K-*O^N-*J. Thus, an electric current is established in the circuit along J->N->0->K-*J (anticlockwise)*. So long the rod JK is kept moving in the magnetic field, the electric current continues to flow in the circuit. It means that an emf is induced in the moving rod which maintains the current in the circuit. Since this emf induced in the rod is due to the motion of the rod, it is also called as the 'motional emf. It is due to the Lorentz forces acting on the free electrons in the moving rod.

Suppose, the induced emf in the moving rod JK is e and the induced current in the circuit is i. We know that when a current-carrying conductor is in a magnetic field, it is acted upon by a force in a direction given by the Fleming's left-hand rule. The magnitude of the force imposed by the magnetic field B on the current-carrying rod JK is given by
F' = i IB,

where I is the length of the rod JK. The force F*' is directed towards left. Hence, to keep the rod moving with a constant velocity v towards right, a force F equal and opposite to F' will have to be applied on it; that is
F = -F' = -ilB.

Suppose, under the force Ft the rod JK undergoes a displacement Ax* in the direction of the force in a time-interval At and comes in the position J 'K'. Then, the work done on the rod will be given by
W =F*.Ax*= F Ax = -HB Ax. But A* = v x Af (magnitude of velocity x time-interval).
W = -HBvAt.
But i x At = q (charge flown through the circuit in time At)
W = -Bvlq.

This work provides the necessary energy for the flow of charge in the circuit. We know that the energy supplied by a cell in flowing unit charge through a circuit is called the emf of the cell. Hence the induced emf e in the rod / K (which is working as a cell in the circuit J N O K J) is given by
e = W/q = - Bv I. ...(i)

In the time-interval At, the area of the circuit increases from JNOKJ to J' N O K' JHence, during this time-interval, the change in the magnetic flux passing through the circuit is given by
A<P_b = magnitude of magnetic field x change in area (JJ 'K'K) = B x (I x Ax).

Hence the rate of change of magnetic flux is
AO_fl Ax
I — O I ~~ .
At At
But Ax/At = v (velocity of the rod). Thus
-tf'Blv. ...(ii)
Comparing eq. (i) and (ii), we get
A<D_fl
^{e =} -~AT■
In the limit At —» 0,
d<b_B
^{e =} ~~dT■

This is Faraday law of electromagnetic induction.

The negative sign signifies Lenz's law. The direction of current (anticlockwise) in the circuit due to the induced emf e is such that the force imposed on the rod (due to the current) opposes the motion of the rod (the motion of the rod is the cause of the current).

It can be seen in the other way also. The direction of current in the circuit is such that the magnetic field produced due to this current is just opposite to the original field B. That is, it opposes the increase in the magnetic flux passing through the circuit (the increase in the magnetic flux is the cause of the generation of current). We may see it from any point of view, the direction of the induced current is always such that it opposes the very cause of its production. This is Lenz's law.

Dimensions of Induced E.M.F.: Numerically, we have
d<b_B ^{e =} ~dT-
, dimensions of e = ₌ ^T^A'*] _{= a} , _A_,
dimensions of t [T]

Organic chemistry articles

Introduction:-
The study of chemistry of carbon compounds is called organic chemistry. According to Lavoisier that all compounds obtained from vegetables and animal sources always contained carbon and hydrogen mainly and nitrogen and phosphorous are also found in some compounds. According to Berzilius organic compounds  are produced from plant and animals only due to presence of some vital force in them.It is called  “Vital force theory”.It is disproved by wholer by producing urea(NH₄ CONH₂) from ammonium cyanate (NH₄CNO)
                                                                 NH₄CNO→ NH₄ CONH₂  
                                   Kolbe synthesized acetic acid (CH₃COOH) from its elements.

Compounds:-

Carbon form millions of compounds due to the following reasons.
1.    High catenation
2.    Tetravalency
3.    Ability to form multiple bonds
4.    Ability to exhibit isomerism

Classification of organic compounds based on carbon skeletion
                     Carbon compounds
Open chain(acyclic)                 (cyclic) closed chain
Aliphatic
Saturated    Unsaturated

Alkanes        Alkenes    Alkynes
Alkanes: Open chain compounds with single bonds between carbon atoms
Ex:  methane and ethane
Alkenes: open chain compounds with atleast one double bond in the carbon chain
Ex: ethylene,propylene
Alkynes: open chain compounds with atleast one triple bond in the carbon chain
Ex:  acetylene,propylene
Alicyclic: Carbon ring with single bond between carbon atoms
Ex: Cyclohexane C₆H₆
Aromatic: planar ring structures with (4n+2)∏ electrons  are called aromatic  according to Huckel rule.Where n is 0,1,2,….
    Ex: pyridine,Furan.

Classification of Carbon compounds on the basis of functional groups:-

Atom or bond or group of atoms in a molecule which is responsible for the characteristic properties of the compound is called functional group

Name	General Formula	Name	Structural Formula
Alkanes	CnH2n+2	Ethane
Alkenes	CnH2n	Ethene
Alkynes	CnH2n-2	Ethyne

Natural Organic Soap

Introduction :
Soap is made by heating animal or vegetable oils with sodium hydroxide. Esters present in fats are broken down to glycerol and sodium salt of fatty acid.

Fat + Sodium hydroxide ------------> Soap + Glycerol

This reaction is called saponification.
Let us discuss the cleaning action of natural organic soap in detail:

Cleaning Action of Natural Organic Soap

The cleaning action of natural organic soap depends on its structure.
E.g. Sodium stearate consists of a long hydrocarbon chain which is hydrophobic (water-hating), attached to an ionic head, which is hydrophilic (water - loving). These molecules dissolve in water because of ionic end to the molecule.

When dissolved in water, the soap molecules lower the surface tension of the water, makiang it wet objects more easily. The molecules also interact with grease and dirt present in the cloth. The hydrophobic hydrocarbon chain is attracted to the grease and become embedded in it. The hydrophilic head of molecule points away from dirt and is attached to water molecule. When water is agitated, the grease is released from the cloth fibre or dish and is completely surrounded by soap molecules. Rinsing with fresh water removes this grease. The use of soap in hard water creates lots of problems because it forms scumbs with hard water. But nowadays synthetic detergents are available which do not scumb witrh hard water. Sodium alkylbenzene - sulphonates were developed in 1970s.

They have a similar long hydrocarbon chain to soap molecules, but the ionic group at hydriphilic head has been changed. The early synthetic detergent molecules were not biodegradable and cause pollution problems in rivers and streams.

Uses of Natural Organic Soap:

• Natural organic soap can be used to avoid or reduce many skin problems.
• Its ingredients have been produced without using fertilizers or pesticides, so it is not harmful to the skin.
• It leaves our our skin feeling clean and moisturised.
• Glycerine, which is a great moisturizer is retained by the natural organic soaps.
• Reduction in the use of toxins helps to create better living environment.
• Most of them are also free from animal fats, which prevents the killing of animals.

Organic chemistry spectroscopy

Introduction 
The study of the interaction between radiation and the matter is called spectroscopy. Molecules in an organic compound have the tendency to absorb specific frequencies according to their structural characteristics. These frequencies can be in the range of visible light, infrared or ultraviolet radiations.

Description of organic chemistry spectroscopy

The electrons in the molecules of an organic compound undergo transition when they absorb or emit light. This is the reason that the color perceived by the organic compounds depends on the absorption of light radiations in the visible range.

Infrared spectroscopy is very successful in organic chemistry.  The types of bonds present in a compound as well as their lattice arrangements can be found by the absorption of IR radiations when they emit thermal radiations. The frequency at which the absorption of the radiation takes place matches the frequency of the vibrating bond.

Nuclear magnetic resonance spectroscopy analyzes the magnetic properties of certain atomic nuclei like hydrogen and carbon which determines their local environments in an organic compound through which the structure of the compound can be determined.

UV spectroscopy is used in highly conjugated organic compounds which absorb UV light or light in the visible regions. When electrons within the atoms are excited from one electronic state to another, their solutions show change in color based on changes in the wavelength due to absorption of visible light by the d electrons. Organic compounds with solvents may either have significant or weak UV absorptions because the pH value and polarity of the solvent do affect the absorption capability of the organic compound.

By passing a beam of IR light through a sample of organic compound the infrared spectrum of the sample can be recorded. On examining the light rays that are transmitted, we get to measure the quantity of energy absorbed at each wavelength. Absorption takes place when the IR frequency is equal to the frequency of the bond. Analysis of these absorption characteristics reveals details about the molecular structure of the sample.

Conclusion for organic chemistry spectroscopy

As complex molecular structures lead to more absorption bands which in turn develops more complex spectra, various types of spectroscopy techniques help in characterization of complex mixtures.

Electricity wind

Introduction

Electric power:- As we know Electric power or elctric current both are same, you have learnt that uncharged boby can be charged by connecting body with a metal wire. In the process of tranfer, charge flows through the wire in a fraction of a second. The flow of electric change constitues an electric currect. With electric power we can run anything like fans, ac , refrigerators, machines, computer almost all the mechanical things you can run by electric power. So electric power is very much important in our daily life.

We are using eletric power almost every second of our daily life and we cannot live without electric power. As we know electric power is not a renewable source of energy we need to produce it own your own. So we have wind energy which is renewable source of energy with the help of wind energy we can produce electric power. This picture show about electric power.

Electricity wind

Wind power :- With the help of wind power we can produce electric power as we know wind blows with the natural phenomenon and we need to source to blow fast wind. Because of different temperature on earht surface wind blows from one direction to another direction and we can utilize this wind energy in different purposes as we can set up a wind turbine and with wind power these turbines will rotate and it will produces mechanical energy and we can use this mechanical energy in any form we can use it by grinding grains , pumping water and most important we can produce electric power by wind energy, just by connecting wind trubines to electric generator we can convert mechanical energy to electrical power. Following figure shows you the image of wind turbine.

Advantages of electric wind power

    As is it renewable source of energy we can produces as much as electric power with the help of wind power just we need to fix wind turbine.
    This is very cheap source of energy and we can produce large amount of electric energy with the help of wind power.
    We can use electric energy produce by wind power in any form.

Static and Current Electricity

Introduction :

The two basic kind of electricity that exist in nature are:  the static electricity and the current electricity.Static electricity is nothing but the collection of uncontrolled electrons which are passing from one body to another body in a movement which is sudden or momentary. Whenever the motion of the electron along a path is a controlled motion then the electricity so produced in the system or circuit is the current electricity.

Examples of static and current electricity

The examples of static electricity:

    The clothes taken out from the dryer and they are stick together

    One can get a shock after walking on the carpet and then suddenly touching something.

The static electricity is generally a nuisance and the hazards of static electricity include the cause of fire. The example of static electricity in which it is produced by rubbing the balloon with the hairs.

Static electricity

Example of current electricity:

The path used in the case of the current electricity is generally a conductor of electricity like a copper wire which can move the electricity from the power plant to the households

Current electricity

Application of Static and Current Electricity

The current electricity is obtained in case when a plug is inserted in a socket, which is generally seen in our homes and this electricity is used to power up the systems like the stereo and the lights. The current electricity is the flow of billions of electrons through the circuit and this flow of electron make a wave of electron which has a voltage of about 120 V. The flow of the current electricity in a system can be taken as the pushing of the electrons through the system through a wire and on the wall on which the socket of electricity is located.

On the other hand, the static electricity occurs only when some of the electrons of a neutral material are moved from their present location to some other location and hence give rise to the electricity and the motion of electron is due to some unknown causes and this electricity is not generally observed. In case of the static electricity no new electron is involved to produce electricity only those electrons which are already there are undergoes some changes hence produces electricity.

A day without electricity

Introduction

A day without electricity is very difficult. Imagining a day without electricity thinking it will be very difficult

Imagine a day without electricity, not just a brief power outage. We all know how inconvenient that day becomes when our electricity is out for only a few hours. How hard it is to remember for that short period of time that the light switch will not produce instant light, the hair dryer will not immediately blow dry our hair, or that we can't even run water into our homes. Our homes and lives have become so dependent on electricity it is really hard to imagine everything that would change without it.

In details

Lifestyles in our own Ozark Mountain region have changed dramatically with the invention of electricity and its establishment into our everyday lives. Have you ever noticed a log cabin built at the very top of a high mountain where it would have a beautiful view? Probably not. Locations were chosen for homes because of accessibility to water, preferably a big spring. Having your home close to a spring meant having cold milk, a cool watermelon in the summer, and plenty of drinking water. Before electricity, a "spring box" would be constructed where the cool spring water would run into it and be deep enough to cover containers of milk, butter, etc. I'm convinced that a spring located close to your home was just about one of the biggest luxuries in those days. Remember, without electricity there were no electric cattle waterers. Drawing water from the well by hand to water a herd of cattle and horses would now seem an impossible task.

A day without electricity
Can we really imagine doing laundry without electricity? Carrying water from the spring, or drawing enough water from the hand-dug water well could prove to quite a day's chore. We really can't imagine the time and effort put into doing a mere "load of laundry" before our electric washers and dryers.

Periodic table alkali metals

Introduction :   

Elements belonging to group 1in periodic table are called alkali metals.  Their outer most electronic configuration is ns1 in periodic table.

Z        Element        No. of electrons

1         Hydrogen             1

3         Lithium                2, 1

11       Sodium               2, 8, 1

19       Potassium           2, 8, 8, 1

37       Rubidium            2, 8, 18, 8, 1

55      Caesium              2, 8, 18, 18, 8, 1

87      Francium             2, 8, 18, 32, 18, 8, 1

The group in a periodic table also includes hydrogen because of the similarity in the electronic configuration with these elements.  They are called alkali metals since they readily dissolve in water to form soluble hydroxides which are strongly alkaline in nature.  The word alkali has been derived from the Arabic word alquili, which means the ashes of plants from which certain compound of the elements sodium and potassium were initially isolated.  Sodium and potassium are abundant while the remaining elements occur only in traces.  The last element francium is radioactive and unstable. 

Alkali metals of periodic table:

They have maximum value of atomic radii, form monovalent  cations and possess the lowest ionization enthalpies  Their hydration enthalpies are low due to their large size. They have low electro negativities and all the members are strongly electro positive.They possess +1 oxidation state, and have low melting and boiling points. They are very light and impart characteristic colors to the flame.They exhibit photoelectric effect. 

They are highly reactive chemically because of their low ionization enthalpies and enthalpy of atomization. They are normally kept in chemically inert solvents such as kerosene.  They form oxide when they combine with oxygen and hydroxide when they react with water.The reaction with water is highly exothermic.So, alkali metals are not kept in contact with water.All alkali metals combine with hydrogen upon heating to form colorless crystalline hydrides that are ionic in nature.They combine with halogens directly to form metal halides. The alkali metals are powerful reducing agents.They are soluble in liquefied ammonia.They react with sulphur and prosperous upon heating to form the corresponding sulphides and phosphides.  

Hydrogen atom consists

Introduction

A hydrogen atom consists of an atom of the chemical element hydrogen. It is an electrically neutral atom which contains a single positively-charged proton and a single negatively-charged electron and they are bound to the nucleus by the Coulomb force. Hydrogen-1, protium, or light hydrogen is the most abundant isotope and it contains no neutrons. There are other isotopes of hydrogen, such as deuterium which contains one or more neutrons.

Niels Bohr in the year 1914 got hold of the spectral frequencies of the hydrogen atom subsequent to making a number of straightforward assumptions. The assumptions were not fully right but they gave up the proper energy answers.

Schrödinger equation and Hydrogen atom

The confirmation of the Bohr's results for the frequencies and underlying energy values were done using Schrödinger equation between the years 1925-1926. The clarification to the Schrödinger equation for hydrogen is systematic. This equation can be used to find out energy levels and thus the hydrogen spectral lines frequencies can be measured. The explanation of the Schrödinger equation goes much advance than the Bohr model nevertheless, for the reason that it also gives way to the shape of the electron's wave function ("orbital") for the various possible quantum-mechanical states, thus clearing up the anisotropic character of atomic bonds. This equation for the hydrogen atom is based on the fact that the coloumb potential which is produced by the nucleus is isotropic in nature. It is radially symmetrical in space and depends on the distance to the nucleus. The resulting eigen energy functions are not isotropic themselves.

Hydrogen ion

In ordinary chemistry, hydrogen is not found without its electron at room temperatures and pressure. Ionized hydrogen is written as "H⁺". Ionized hydrogen in case of the salvation of classical acids like hydrochloric acids forms hydronium ion. Hydronium ion is written as H₃O⁺. This refers to the entire hydronium ion and to a single ionized hydrogen atom. In this type of case, the proton is transferred by acid from water to the hydronium ion. This type of ionized hydrogen without their electron or free protons is commonly observed in the solar wind and interstellar medium

The nucleus of an atom contains

An atom is constructed of three major particles; two of them are in a central region or core called the atomic nucleus. The third type of particle is in the region surrounding the nucleus. The weight or mass of the atom is concentrated in the nucleus. The nucleus of the atom contains the protons and the neutrons, which are the massive particles of the atom. One type of particle located in the nucleus is the neutron.

Introduction 

Neutrons were named to reflect their lack of electrical charge. They are neutral. Protons, the second type of particle in the nucleus in certain areas called  enegry levels are the electrons. Each electron has a negative electrical charge. The number of electrons determine the space that an atom occupies.

Charge of an atom

The charge of an atom is neutral if the number of positively charged protons equals the number of negatively charged electrons. For instance, hydrogen with 1 proton, would have 1 electron; carbon with 6 protons would have 6 electrons. You can determine the number of either of these two particles in a neutral atom if you know the number of other particles.

Identity of the element
All the atoms of the same element have the same number of protons. The number of protons determine the identity of the element. For example, carbon always has 6 protons and no other element has that number. Oxygen always has 8 protons. The atomic number of an element is the number of protons in an atom of that element; therefore, each element has a unique atomic number. Because this is an extremely small mass and is awkward to express, 1 proton is said to have a mass of 1 atomic mass unit.

Neutral atoms
Although all the neutral atoms of the same element have the same number of protons and electrons, they do not always have the same number of neutrons. In the case of oxygen, over 99% of the atoms have 8 neutrons, but there are others with more or fewer neutrons. Each atom of the same element with a different number of neutrons is called an isotope of that element. Since neutrons have a mass very similar to that of a proton, isotopes that have more neutrons will have a greater mass than those that have fewer neutrons.

Isotopes
Elements occur in nature as a mixture of isotopes. The atomic weight of an element is an average of all the isotopes present in their normal proportions. For example, of all the isotopes present in their normal proportions. For example, of all the hydrogen isotopes on Earth, 99.985% occur as an isotope without a neutron and 0.015% as the isotope with one neutron.There is a third isotope with two neutrons but it is not considered because it is highly unstable. When the math is done to account for the relative amounts of the various isotopes of hydrogen, the atomic weight turns out to be 1.0079 AMU.

Mass number of an atom
The sum of the number of protons and neutrons in the nucleus of an atom is called the mass number. Mass numbers are used to identify isotopes. A hydrogen atom with 1 proton and 1 neutron has a  mass number of 1 + 1, or 2, and is reffered to as hydrogen-2 ( also called deuterium). A hydrogen atom with 1 proton and 2 neutrons has a mass number of 1 + 2 , or 3, and is referred to as hydrogen-3 ( also called tritium).

3 particles of an atom

Hi There are 3 main particles of an atom. They are electrons, protons and neutrons.

Introduction to 3 particles of an atom

Protons
Protons are the most elementary particles of an atom.
They are situated in the nucleus.
They carry single positive charge.
In fact, charge carried by a proton has been labeled as single charge.
How do all the protons, which are similarly charged stay composed in the nucleus?
It is because of energy called binding energy.
The number at the base of an atom represent the atomic number.
e.g.In case of carbon ₆C, the atomic number is 6, which means number of protons is 6.

Neutrons

They are nuclear particles with mass nearby that of protons but no charge.
Since they are part of mass number along with the protons, the number of neutrons is equal to,
Mass number - Number of protons.
e.g: The mass number of Krypton is 84 and the number of protons is 36.
So the number of neutrons =  84 - 36 = 48
Mass number is written at the top of the symbol of the element.

Electrons

Electrons are negatively charged subatomic particles.

The charge is −1.602×10⁻¹⁹ Coulomb.
Their mass is 1/1836 ^th of that of proton and is many a times neglected in related calculations.
Electrons are rotating outside the nucleus of an atom. They are arranged in sub-shells in different energy levels.

The energy levels are named as K, L, M, N etc.., and the sub-shells as s, p, d, f etc.., Electrons posses a spin of +1/2 or -1/2.

Electrons are elementary particles and are not composed of quarks. They were discovered by J.J.Thompson in 1897.

Electricity is actually flow of electrons.
Chemical bonds are formed either by donating, accepting or sharing of electrons.
As the number of electrons is same as that of protons, the atom attains stability as the opposite charges attract one another.
Thus the number of electrons can be found from the number of protons.

Iron atom

Introduction 

Iron atom is a chemical element having atomic number 26 and with the symbol ‘Fe’ which in Latin means ferrum.  It is a metal in the first transition series.  Like other ‘group 8’ elements, it exists in several oxidation states. The oxidation states of iron is +2 and +3, it might also occur in higher oxidation states of about +6.  Iron (II) compounds are called ferric and iron(III) compounds are called ferrous.   Iron and its alloys are the widely used ferromagnetic materials in the modern day life.

Pure iron is softer than aluminum.  Steel can be prepared by alloying pure iron with small amounts of other metals and carbon. The alloy steel is almost 1,000 times harder than pure iron.  It is the most common element found on earth.  It reacts with air to form iron oxides also known as rust. The rusting of iron and its alloys is undesirable, and has a major economic impact. The melting point of iron is about 1535 °C. Its mechanical properties can be varied extensively by varying the carbon content in the alloy.

      Different types of Iron are

1.   Pig iron has 3.5–4.5% carbon
2.   Cast iron contains 2–4% carbon 
3.   Wrought iron has less than 0.008% carbon

Occurrence and Biological Importance of Iron atom

Occurrence of Iron atom: Iron is the fourth most abundant element in the Universe, formed from the process known as nucleosynthesis, by the fusion of silicon in huge stars. Metallic iron is rarely found on the surface of the earth because it tends to oxidize, but its oxides are diffused and represents the primary ores. About 5% of the earths curst constitutes of Iron.  Most of the Inner and outer core of earth consists of Iron-Nickel alloy which is about 35% of the total mass of the earth.  Hematite and Magnetite are the most common form of iron ore which is found in earth crust. These ores are combined with oxygen to form iron oxides. 

Biological importance of Iron atom: Iron plays a major role in biology.  Ranging from the primitive archaea to humans, all living organism has iron-proteins.  Hemoglobin is a protein containing iron.  Hemoglobin is responsible for the color of the blood.  Hemoglobin and myoglobin are the two compounds which helps in the transportation of oxygen proteins in vertebrates.  Iron is present in each and every cell of the human body. It is the basic necessity for the growth and development of a living organism.

Applications of Iron

Alkaline earth metals chemical

Introduction :
Alkaline earth metals are beryllium, magnesium, strontium, calcium, barium, and radium. These are the chemical elements that occupy the second column in the periodic table. In olden days when substances were insoluble in water and unchanged by fire they were referred to as earths. Thus the name uses of alkaline Earth metals.

Alkaline earth metals:

The alkaline-earth elements have a grey-white lustre when freshly cut. This lustre is tarnished readily when exposed to air. These metals are good conductors of electricity and highly metallic and. Beryllium is hard enough to scratch glass.

http://www.britannica.com/EBchecked/topic/53345/bariumBarium is the least hard of them all. The elements in this group have higher melting points and boiling points than those of the corresponding alkali metals;  and beryllium has the highest boiling and melting points(MP 1,283° and bop about 2,500°) and magnesium has the lowest boiling and melting point in this group (MP 650° C and bp 1,105° C)

Occurrence in Nature

• Magnesium and calcium are essential to all living organisms and found in abundance in several compounds.While calcium is needed for bone and teeth formation, magnesium is needed for the intercellular processes and enzyme formation in the body.
• Beryllium is least soluble and is very rarely found in nature. It is a toxic metal.

• Strontium and barium are less available. Strontium is found in marine aquatic life, like hard corals. Barium is used in some imaging studies.

• Radium is highly radioactive metal and has a low availability. Exposure to radium can be dangerous to life.

Alkaline earth metal compounds:

 The alkaline earth metals react with other elements to form compounds that are used in several applications. For example
Alkyl magnesium halides are used to synthetize organic compounds. Calcium carbonate is used for making limestone, marble, and chalkin the construction industry.Magnesium oxide (MgO) is used in wire insulation and as a material to refract furnace brick.

Conclusion on alkaline earth metals:

The alkaline earth metals are a useful group of metals. There are differences in physical properties among these metals. A detailed study of these metals gives new insights into the behaviour of these metals and the chemical differences between them.

Alkanes physical and chemical properties

Introduction :   
Hydrogen atoms in a hydrocarbon aliphatic are perfumed by halogen atoms' consequences in the configuration of alkyl halide and aryl halide correspondingly. Haloalkanes have halogen atoms attached to the SP³ hybridised carbon atoms of an aryl group. Several halogens have organic composite which occur in nature and several of these are clinically useful. These classes of compounds locate wide applications in industry as well as in day-to day life.

Physical properties:

Physical properties:
Alkyl halides will be colourless while pure. Though bromides and iodides expand colour when exposed to light,several volatile halogen compounds contain sweet smell.

Melting and boiling points in physical properties:
Methyl chloride, methyl bromide, ethyl chloride also several chlorofluoromethanes are gas by room temperature. Higher members are liquids or solid. Since, we learnt that the contain, molecules of organic halogen mix are usually polar, suitable to greater polarity as well as higher molecular mass like evaluating to the parent hydrocarbon, the inter molecular forces of attraction are stronger in their halogen derived. The attractions get stronger as the molecules get bigger in size containing  more electrons.

Density in physical properties:
Bromo, iodo and polychloro derived of hydrocarbons are heavier than water. Physical properties of density increases among increase in number of carbon atoms. Halogen atoms with atomic mass of the halogen atoms.

Chemical properties:
Chemical Reactions of alkanes:
The chemical reactions of alkanes may be divided into the following categories:

• Nucleophilic substitution
• Elimination reactions
• Reaction with metals

Nucleophilic substitution in chemical reactions:
A nucleophile reacts with alkane having a partial positive charge on the carbon atom bonded to halogen. A substitution reaction obtain position with halogen atom known leaving group departs as halide ion.

Elimination reactions in chemical reactions:
When an alkane with B-hydrogen atom is heated among alcohilic solution of potassium hydroxide, here is removal of hydrogen atom from B-carbon and a halogen atom from the a-carbon atom.
Alkane is produced the product B-hydrogen atom is occupied in elimination, it is often known B-elimination.

Relation with metals in chemical reactions:
Mainly organic chlorides, bromides and iodides react with definite metals to provide compounds containing carbon-metal bonds. Such compounds are known as organo-metalli compounds.

Radio wave propagation

Introduction :
A radio wave is an electromagnetic wave whose frequency is lower than 3000 GHz, a wavelength greater than 0.1 mm.

The field of radio is regulated by the International Telecommunication Union (ITU) has established rules of radio communications in which one can read the following definition:

Radio waves or radio waves "electromagnetic waves with frequencies arbitrarily lower than 3000 GHz propagated in space without artificial guide" can be between 9 kHz and 3000 GHz which corresponds to wavelengths 33 km to 0.1 mm.

The wave frequency below 9 kHz radio waves are, however are not regulated.

The radio waves  are electromagnetic waves which propagate in two ways:
  * In the free space propagation (radiated around the Earth for example)
  * In lines (guided propagation in a coaxial cable or waveguide)

The field frequency radio waves ranges from 9 kHz to 3000 GHz.

Radio or electromagnetic wave in space :

The waves caused by a falling rock on the surface of a pond spread like concentric circles. The radio waves emitted by the isotropic antenna (that is to say, radiating uniformly in all directions in space) can be represented by a series of concentric spheres. One can imagine a balloon inflating fast, the speed of light c, very close to 300,000 km / s. After one second, the sphere has 600,000 km in diameter. If the propagation medium is not isotropic and homogeneous, the wave front will not be a sphere. As the radio wave is a vibration, after a period, the wave has traveled a distance denoted lambda and called wavelength. The wavelength is a key feature in the study of the spread, for a given frequency, it depends on the speed of wave propagation.

Radio Wave propagation in a line:

A generator connected to a load with a line will cause each of the two conductors of the line to establish an electric current and the formation of a wave moving in the dielectric at high speeds. This speed is less than the speed of light but frequently exceeds 200 000 km / s, which implies that for a given frequency, the wavelength in the line is smaller than in space.

In a coaxial line, the propagation speed is the same regardless of frequency, we say that the line is dispersive.

Propagation of electromagnetic waves

Propagation of Waves

 The process of communication involves the transmission of information from one location to another.  As we have seen, modulation is used to encode the information onto a carrier wave, and may involve analog or digital methods. It is only the characteristics of the carrier wave which determine how the signal will propagate over any significant distance.  This chapter describes the different ways that electromagnetic waves propagate.

Basics

An electromagnetic wave is created by a local disturbance in the electric and magnetic fields.  From its origin, the wave will propagate outwards in all directions.

If the medium in which it is propagating (air for example) is the same everywhere, the wave will spread out uniformly in all directions.

Far from its origin, it will have spread out enough that it will appear have the same amplitude everywhere on the plane perpendicular to its direction of travel (in the near vicinity of the observer). This type of wave is called a plane wave. A plane wave is an idealization that allows one to think of the entire wave traveling in a single direction, instead of spreading out in all directions.

Electromagnetic Wave Propagation at the speed of light in a vacuum. In other mediums, like air or glass, the speed of propagation is slower. If the speed of light in a vacuum is given the symbol c0, and the speed in some a medium is c, we can define the index of refraction, n as: 
Refraction

When the wave enters the new medium, the speed of propagation will change. In order to match the incident and transmitted wave at the boundary, the transmitted wave will change its direction of propagation.  For example, if the new medium has a higher index of refraction, which means the speed of propagation is lower, the wavelength will become shorter (frequency must stay the same because of the boundary conditions).  For the transmitted wave to match the incident wave at the boundary, the direction of propagation of the transmitted wave must be closer to perpendicular.

The relationship between the angles and indices of refraction is given by Snell's Law:
ni sinI = nt sint

Alkane nomenclature practice

Introduction :
Alkanes are the saturated hydrocarbons consisting elements of carbon (C) and hydrogen (H) in which atoms are linked together by single bonds. Alkanes are the member of a homologous series of organic compounds, where all members differ by a constant relative molecular mass of 14.

Each carbon atom have 4 single bonds (either C-H or C-C bonds), and each hydrogen atoms are joined to a carbon atom. A series of linked carbon atoms is known as the carbon skeleton or carbon backbone...The first member of alkane is methane, CH₄.

Structure and Isomerism of Alkanes:

Saturated hydrocarbons, Alkanes, may occur in linear, branched or cyclic forms. Alkanes having linear structure must have n<3.In this all the carbon  are attached  in a snake-like structure and alkanes having branched structure must have n>3. Alkanes having cyclic structure must have n>2.Alkanes having more than three carbon atoms are arranged in number of ways, so they form different structural isomers.

• First three members i.e. methane, ethane, and propane have one isomer.  
• Butane ,C₄H₁₀ has 2 isomers. they are n-butane, isobutene
• Pentane ,C₅H₁₂  has 3 isomers. They are pentane, isopentane, neopentane 
• Hexane, C₆H₁₄ has five  isomers
• Branched alkanes are chiral, e.g., 3-methylhexane and its higher homologues

Alkane nomenclature practice

• The number of carbon atoms can be indicated by ‘meth’ for one carbon atom, ‘eth’ for two , ‘prop’ for three, ‘but’ for four , ‘pent’ for five and so on…..

• Alkanes or saturated carbon atoms can be named by adding ‘ane’ suffix to the number of carbon atoms’ name. e.g., CH₄ can be named as methane. C₂H₆ can be named as ethane .First three members of alkanes form linear structure, so they have one isomer each.  

    Butane has two isomers. It can be named by using following rules:

• For naming branched chain isomers, firstly number of carbon atoms in series are counted and named according to it.

• Then number of methyl group is counted and also its position is located.

As per the IUPAC convention, we have certain rules to follow:

• First we have to find and then name the longest chain of carbon.
• Next we have to identify the groups which is being attached to the chain, after that we name it.
• Number the C- atoms in a chain that starts from the nearest substituent group.
• Assign the position of each group by a proper number and then we name it.
• Write the name of the listing groups which should be in an alphabetical order.
• di, tri, tetra, are used as prefix to assign several groups of similar kind. Alphabetizing is not taken into account.

E.g.  
1. C₄H₁₀           `->`     common name – n-butane      IUPAC name- butane 

 

2.

 

IUPAC names of the above alkane is 2- methylpropane

3.

IUPAC name of the above alkane is 2-methylbutane

4.

IUPAC name of the above alkane is 2,2-dimethylpropane

Conclusion for the nomenclature of alkane

From the discussion, we conclude that, in alkane each carbon atom have 4 single bonds and each hydrogen atom must be joined to a carbon atom .There is single bond between each carbon atom. They are saturated hydrocarbons.

Nomenclature of coordination compounds

Define nomenclature:
Nomenclature is significant in the coordination of chemistry because of the need to have an unambiguous method of describing formula and writing systematic names, particularly when dealing with isomer. The formulas and names adopted for ordination entities are based on the recommendation of the international union of pure and applied chemistry. A complex is an essence in which a metal atom or ion is linked with a collection of neutral molecules or anions call ligands.

Formulas of mononuclear coordination entities:

The formula of a compounds is shorthand tools used to provide basic information about the constitution of the compounds in the concise and convenient manner. Mononuclear synchronization entities include a particular central metal atom. Nomenclature coordination compounds are neutral substances in which at smallest amount one ion is absent as a complex.

• The central atoms is listed first
• The ligands are then listed in alphabetic order.
• Polydentate ligands are also scheduled alphabetically.
• The method for the complete coordination unit, whether charged or not is together with this in square brackets.
• There should be no space between the ligands and metal within the coordination.

Naming of mononuclear coordination compounds:

• The names of nomenclature coordination compounds are derivative by subsequent the principle of additive nomenclature. Thus the groups that surround the central atoms must be identified in the name.
• The cation is named primary in together positively and negatively charged coordination entity.
• The ligands are name in an alphabetical organize prior to the name of the central atom/ion.
• Names of the anionic ligands end in –o those of neutral and cationic ligands are the same except aqua for H₂O, ammine for NH₃, carbonyl for CO and Nitrosyl for NO. These are placed within enclosed marker ().
• When the name of the ligands include a numerical prefix, then the terms, bis, tris, tetrakis are used, the ligands to which they refer being placed in dichlorobis.
• Oxidation state of the metal in cation, anion or neutral coordination entities is indicating by Roman numeral in parenthesis
• If the complex ion is a cation, the metal is named same as the element. The neutral complex is named similar to that of the complex cation.

Making molar solutions

Introduction :
The amount of substance present in unit amount of the solution is called concentration of the solution.  Generally, concentration of a solution is expressed in
(a) molarity, M     (b) molality, m  or    (c) normality, N
Molarity:
“The number of gram molecular weight of the solute present in 1000 cm³ (or 1 dm³) of the solution is called molarity”.  It is denoted by the symbol M.

Making molar solutions Case1 and 2

Case 1:
Suppose 1 mole of Oxalic acid crystals (H₂C₂O₄. 2H₂O, Molecular weight 126g) is dissolved in 1dm³ of the solution. Molarity of the solution is 1.
Molarity of the solutions can be calculated from the expression
Formula for Molarity = (mass/dm³) / molecular weight
Case 2:
Suppose ‘x’ molar solution of Oxalic acid is asked to prepare.  Then, the weight of the Oxalic acid corresponding to ‘x’ mole of Oxalic acid is used in making x molar solution.
That is weight of Oxalic acid required is = ‘x’ moles X molecular weight of Oxalic acid
                                                                        = molarity X 126g
This much of Oxalic acid should be dissolved in 1 dm³ of solvent.

Making molar solutions Case3 ,4 and relation between molarity & normality

Case 3:
For the making of  ‘x’ molar solutions of Oxalic acid of a volume, say 100ml, the weight of the oxalic acid required is found using the below relation.

Case 4:

If a liquid reagent of certain % assay and density is given in the making of certain molar solutions, then the strength of the given liquid reagent should be determined first.  This is done by using the relation.

Strength = number of moles / dm³
               = (weight in g / Molecular weight) / dm³
               = density / Molecular weight
Now, the strength of the liquid reagent given is used in the making of the solution of required strength and volume using the below relation.
M₁.V₁ = M₂ V₂
Where:
M₁, M₂ are the molarities of the given liquid reagent and solution to be prepared
V_1, V₂ are the volumes of the given liquid reagent and solution to be prepared, respectively.
Since, Equivalent weight and Molecular weight are related as:

So, there exists a relation between the molarity and normality as below:
Molarity = (mass/dm³) / Mol. Wt
               = (mass/dm³) / [Eq. wt x valence (number of electron exchange)]
Molarity = Normality / valence    or
Normality = Molarity X valence         is used in the making of N solutions from M solutions.

Mass and volume relationship

Introduction 
Mass is the measure of inertia.  Mass of an atom is composed of the mass of the protons and the mass of the neutrons.  The mass of the electrons is negligible. It is the same thing with molecules.   The mass of a particular compound is the mass of its molecules.

 Similarly, volume is also a property exhibited by any gas. It is the space occupied by a gas.  Each gas at a certain temperature has a specific volume depending upon its mass. There is a certain co-relationship between mass and the volume of the gas at a particular temperature.

Mass and molar mass definition :

In chemistry, the mass is often expressed in terms of molar mass. The molar mass is the mass of one mole of a gas.  One mole of a gas is nothing but gram equivalent of the gas.
 To illustrate, take the gas, carbon monoxide, the molar mass of carbon monoxide is 12+ 16 = 28. 

When this mass which is in atomic mass unit is expressed in grams instead of atomic mass unit it is called as one mole. 

So one mole of carbon dioxide is 28 grams. And it has been proved that there is definite relationship between the volume and molar mass of the gas.

The relationship between the molar mass and the volume is that 1 mole of the gas would occupy 22.4 liters of volume. 

In the above case where the molar mass of carbon dioxide is 28, 28 grams of carbon dioxide would occupy 22.4 liters of volume.  This relationship was developed from the equation of ideal gas i.e. PV = nRT, where 'n' is number of moles. 

At standard temperature and pressure the values of which are 273° kelvin and 1 atmosphere, the volume figure derived is 22.4 liters. 

If the mass of a gas is expressed as 'z' then it can be said that 'z' grams of a gas occupy (z/molar mass x 22.4) liters of volume.

Illustration of mass and volume relationship

Find the volume occupied by 56 grams of carbon dioxide.
The molar mass of carbon dioxide is 28;
hence number of moles = 56 / 28 = 2 moles.
 Since one mole occupies 22.4 liters at STP,
2 moles of carbon dioxide would occupy 44.8 liters of volume.

Amplitude Modulation Side Band

Introduction :-

Modulation is the process of changing one or more properties like amplitude, frequency, phase of high frequency carrier wave in accordance with the Modulating wave. Here the Modulating wave is base-band signal. Example of base-band signal is speech or music signal.

what is amplitude modulation : Amplitude Modulation is the process of changing Amplitude of high frequency carrier wave in accordance with the Amplitude of Modulating wave.

Definition of Side-Band:

A group of frequencies which is having frequency fc±fm is called as Side-Band. Here fc=Carrier frequency and fm=modulating frequency. fc+fm is called as upper side-band and fc-fm is called as lower side-band.

Different types of Amplitude Modulation

Depending on side-bands we have 5 different types of Amplitude Modulation.

1. Double-Sideband Full Carrier

2. Single-Sideband Full Carrier

3. Single-Sideband Reduced Carrier

4. Vestigial-Sideband

1. Double-Sideband Full Carrier:

The technique of amplitude modulation in which along with the carrier if both upper side-band and lower side-band is transmitted then that amplitude modulation is called as Double-Sideband full carrier.

In order to increase the efficiency of transmitter we may suppress the carrier from this DSB-AM then that technique is called as Double-Sideband Suppressed carrier Amplitude Modulation Method.

This type of amplitude Modulation is also called as conventional amplitude modulation

2. Single-Sideband Full carrier:

The technique of amplitude modulation in which single side-band is transmitted is called as single-sideband Full carrier and is denoted as SSB.

This type of modulation technique is used in shortwave radio or shortwave broadcasting

3. Single-Sideband Reduced Carrier:

The technique of amplitude modulation in which carrier and single side band is suppressed then that type of amplitude modulation is called as single-sideband Reduced carrier.

This type of modulation technique is used in amateur radio.

4. Vestigial-Sideband:

The technique of amplitude modulation in which part of single side band and all other remain as it is ,then that type of amplitude modulation in called as vestigial side-band.

This type of modulating technique is used in transmission of Television i.e., Television broadcasting.

kinetic energy of a particle

In physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working" is a quantity that can be assigned to every particle, object, and system of objects as a consequence of the state of that particle, object or system of objects. Different forms of energy include kinetic, potential, thermal, gravitational, sound, elastic, light, and electromagnetic energy. The forms of energy are often named after a related force. German physicist Hermann von Helmholtz established that all forms of energy are equivalent - energy in one form can disappear but the same amount of energy will appear in another form. Energy is subject to a conservation law. Energy is a scalar physical quantity. In the International System of Units (SI), energy is measured in joules, but in some fields other units such as kilowatt-hours and kilocalories are also used.

Any form of energy can be transformed into another form. When energy is in a form other than heat, it may be transformed with good or even perfect efficiency, to any other type of energy. With thermal energy, however, there are often limits to the efficiency of the conversion to other forms of energy, due to the second law of thermodynamics. As an example, oil is reacted with oxygen, potential energy is released, since new chemical bonds are formed in the products which are more powerful than those in the oil and oxygen.

The released energy resulting from this process may be converted directly to electricity (as in a fuel cell) with good efficiency. Alternately it may be converted into thermal energy, if the oil is simply burned in order to heat the combustion gases to a certain temperature. In the latter case, however, some of the thermal energy can no longer be used to perform work at that temperature, and is said to be "degraded." As such, it exists in a form unavailable for further transformation. The remainder of the heat may be used to produce any other type of energy, such as electricity.

In all such energy transformation processes, the total energy remains the same. Energy may not be created nor destroyed. This principle, the conservation of energy equation, was first postulated in the early 19th century, and applies to any isolated system. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.

Although the total energy of a system does not change with time, its value may depend on the frame of reference. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy (and higher total energy) relative to the Earth.

Kinetic Energy of Gasses

Introduction :
Let us see about the kinetic energy of gases. In continuous motion, molecules also exert strong electric forces on one another when they are close together. The forces are both attractive and repulsive. The former hold molecules together and the latter cause matter to resist compression. The kinetic theory can explain the existence of the solid, liquid and gaseous states.

Two ways of measuring kinetic Energy:

The energy produced by a body by virtue of its motion is called kinetic energy. A moving body gives kinetic energy. For example bullet shot forms a rifle, flossing water of a river, blowing wind have kinetic energy. A moving body can do work due to its kinetic energy. For example the kinetic energy of a hammer is used to drive a nail in wooden block; the kinetic energy of air may be used to run wind mills, the kinetic energy of a bullet fired from a gun can pierce a target.
The kinetic energy of a body may be measure in two ways.

• By calculating the work required by an external agent to set the body into motion from the state or rest.
• By calculating the work done by the moving body against dissipative force before it comes to rest.

Kinetic Energy of Gases:

The molecules in gases are much farther apart than in solids or liquids and so gases are much less dense and can be squeezed into a smaller space. The molecules dash around at very high speed about 500m/s in all the space available. It is only during the brief spells when they collide with other molecules or with the walls of the container that the molecular forces act.

A model of a gas is shown in figure. The faster the vibrator works the more often the ball-bearings have collisions with the lid, the tube and with each other, representing a gas at a higher temperature. Adding more ball-bearing is like pumping more air into a tyre. If a polystyrene ball is dropped into the tube its irregular motion represents Brownian motion.

Benzene molecular formula

Introduction :
Carbon has valency of 4.Hydrogen has valency of 1.Untill the discovery of benzene,no compound with find empirical formula C_nH_n was discovered.As such benzene with same empirical formula posed a great challenge.It was predicted that the molecule would invariably contain unsaturation.

Progressive attempts on benzene molecular formula

Since it was first isolated and identified in 1825,the knowledge of structure of eluded the chemists for many decades

The existence of double bond in ethene was discovered by Scottish chemist Alexander Brown in 1864.However the discovery of the probable structure of C6H6 continued to dodge the chemists.It was so because never before was any structure derived for a compound with the empirical  formula C_nH_n.
The chemists were confused as to how all the valencies of carbon would stand satisfied in such a compound.

Kekule's contribution in benzene molecular formula

Simultaneously attempts were also made by Adolph Carl Ludwig Clause ,Henry Armstrong etc. to propose certain structures.However they failed.

It was only in 1865 that Kekule could make a breakthrough in devising this structure.He devised the structure with hexagonal ring. He said that he had discovered the ring shape of the benzene molecule after having  day-dream of a snake seizing its own tail .

This structure  met with lot of criticism in the beginning and was further refined.In 1872 he put forth that the atoms are oscillating and were in reverse and forward collision with the neighbouring carbon atoms.

pi bonds in benzene

Kekule put forth the correct structure in 1865.According to it ,benzene has aromatic structure. He revealed that he had discovered the ring shape of the benzene molecule after having  day-dream of a snake seizing its own tail .This structure  met with lot of criticism in the beginning and was further refined.
The only way in which this could be explained is pi bonds in the aromatic ring.

Unconventional pi bonds

It means it consists of a conjugated planar ring system with delocalized pi electron clouds.These electtrons which form the double pi bond keep on 'hopping' between subsequent bonds.This also can be expressed in following sentence.

The electrons for C–C bonding are distributed equally between each of the six carbon atoms.
Average length between the C-C and C=C is at 0.139 nm. This is called as 'resonance'. Resonance adds to the energy of the structure. As a result benzene is more stable by 150 kJ mol^-1than predicted by Kekule because of resonance.

Each carbon atom is attached to one hydrogen atom in addition to two carbon atoms.The electrons of the pi bonds keep on oscillating forth and back.In this way an the valencies of the atoms stand satisfied,albeit in a unconventional way.Thus in order to facilitate this,the structure would be planar and not three dimensional.This enhanced stability is the fundamental property of aromatic molecules that differentiates them from non-aromatic molecules.

Because of these pi bonds, benzene undergoes nucleophilic as well as electrophilic addition reactions at one end of any double bond.

Structure with respect to moleculr formula

The structure of benzene has aromatic nature.
It means it consists of a conjugated planar ring system with delocalized pi electron clouds.The electrons for C–C bonding are distributed equally between each of the six carbon atoms. Each carbon atom is attached to one hydrogen atom.The electrons of the pi bonds keep on oscillating forth and back.In this way an the valencies of the atoms stand satisfied,albeit in a unconventional way.Thus in order to facilitate this,the structure would be planar and not three dimensional.This enhanced stability is the fundamental property of aromatic molecules that differentiates them from non-aromatic molecules .

The discovery of ring structure of benzene has led to vast field of aromatic compounds in organic chemistry. Many important chemicals are derived from benzene by replacing one or more of its hydrogen atoms with another functional groups.e.g toluene,phenol etc.The ring structure is also the basic unit of many biochemicals like hormones.