Specific Heat Cv

Introduction:

Molar specific heat capacity of a gas at constant volume Cv is defined as the quantity of heat required to raise the temperature of one mole of a gas through 1 K keeping its volume constant.
Specific heat Cv of ,monoatomic , diatomic are discussed here.

Specific Heat Cv of Monoatomic Gases:

Monoatomic gases like argon helium have three degrees of freedom.
We know , kinetic energy per molecule , per degree of freedom is `1/2` kT
Therefore kinetic energy  per molecule with three degrees of freedom is `3/2` kT
Total kinetic energy of one mole of the monoatomic gas is given by
 E =`3/2` kT* N
    = `3/2` RT, where N is Avogadro number
 `(dE)/(dT) = 3/2R`
If dE is small amount of heat required to raise the temperature of 1 mole of the gas at constant volume, through a temperature dT
dE = 1 x Cv x dT
Cv = = `(dE)/(dT) = 3/2 R`
As R = 8.32 J mol^-1K^-1
Cv = `3/2` 8.31
Cv = 12.465 J mol^-1 K^-1
Cp is molar specific heat at constant pressure.
Then Cp –Cv = R
Cp = CV +R
     = `3/2`  R +R = `5/2` R = `5/2`  x 8.32 = 20.775 J mol^-1K^-1

Specific Heat Cv of Diatomic Gases:

In diatomic gases like hydrogen , oxygen , nitrogen etc, a molecule has five degrees of freedom. Hence the total energy associated with one mole of diatomic gas is
     E = 5 x `1/2` kT x N = `5/2` RT
Also Cv = `(dE)/(dT)`  = `d/(dT) (5/2 RT)`
              = `5/2` R
Cv = `5/2` x 8.31 = 20.775 Jmol^-1K^-1 
But Cp = Cv +R
            = `5/2` R +R
            = `7/2` R
            = `7/2` x 8.31 = 29.0.85 J mol^-1K^-1

Heat Transfer Designs

Introduction :

Heat transfer:- There are three modes of heat transfer for different form of substance we have different method of transfer of heat. Like for solids mode of transfer of heat is conduction. Conduction is a process of heat transfer in solids. In this process, heat is transferred from particles to particles of the solid, without the actual movement of the particles.

 

We can see the simple experiment for this

1. Put drops of wax at regular intervals on an iron rod( or any other metal).
2. Heat one end of the rod over a candle flame.
3. Repeat the procedure using a plastic rod.

Observation and Conclusions for Heat Transfer

Observation:

1. With the metal rod:- the drop nearest to the flame melts first, one by one all the drops melts, and the end of the rod opposite to the flame begins to feel warm to the touch.
2. With plastic rod :- the end closer to the flame begins to melt while the wax drops remain unaffected. Also, the rod does not feel warm to the touch.

Conclusion:

1. Certain material for example allows heat to pass through them while certain material does not.
2. The heat is transferred from particles to particles themselves moving. This is inferred from the fact that the entire rod does not get heated at once. The wax drops melt one by one gradually. This mode of heat transfer is called conduction.

Heat Transfer by Convection

Convection:- convection is the transfer of heat through a body by the hot particles themselves moving from place and place.
Transfer of heat by convection takes place in liquid and gases only. It does not occur in solids because the particles in solids are not free to move about.
One example when a beaker of water containing a crystal of potassium permanganate is heated over a low flame, an upward current of colored water is seen rising from the point where heat is applied. This colored stream reaches the top, spreads out and circulates down the sides of the beaker.
These were the some points related to heat transfer. Knowledge of this much is very important.

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.

Sulfur Dioxide Chemical Formula

Introduction to Sulphur dioxide:

The chemical formula of sulphur dioxide is SO₂. Molar mass of sulphur dioxide is 64.07g. Sulphur dioxide is a colorless gas with irritating and suffocating smell. Its meting and boiling point are -75.5˚ and -10˚C. Sulphur dioxide can be produced by some industrial processes and also by volcanoes.  Coal and some petroleum contain sulphur, so the combustion of coal and petroleum produces sulphur dioxide. The oxidation of sulphur dioxide can be carried out in presence of catalyst like NO₂ which forms H₂SO₄ that leads to acid rain.
The molecular formulas of the sulphur dioxide is as shown below,

Preparation of Sulphur Dioxide:

Sulphur dioxide can be prepared in many differnt methods; few of them are as follows

• It is prepared by burning sulphur in atmosphere.

S₈ + 8 O₂ ===> 8 SO₂

• It is also prepared by burning or roasting iron pyrites in air.

4 FeS₂ + 11 O₂ ===> 2 Fe₂O₃ + 8 SO₂.

• It is prepared in laboratory by heating copper turnings with concentrated H₂SO₄

Cu + 2H₂SO₄ ===> CuSO₄ + SO₂ + 2H₂O.
Reactions of sulphur dioxide:

• Sulphur dioxide reacts with alkali solutions to give sulphites.

SO₂ + 2 NaOH ===> Na₂SO₃ + H₂O

• Sulphur dioxide reacts with halogens and gives sulphuryl chloride.

SO₂ + Cl₂ ===> SO₂Cl₂.

• Hydrogen sulphide reduces sulphur dioxide and gives sulphur element.

SO₂ + 2 H₂S ===> 3 S + 2 H₂O.

Structure and Bonding in Sulphur Dioxide:

Sulphur dioxide is a bent shaped molecule with O-S-O bond angle 119˚ and the bond length of S-O is 143.1 pm. The sulphur atom is sp² hybridized. The oxidation state of sulphur is +4.
The possible resonance structures of Sulphur dioxide SO₂.

Uses of Sulphur dioxide (SO₂):

• Sulphur dioxide is used in the production of sulphuric acid.
• It is used as a preservative for dried fruits and apricots.
• It is used as a reducing agent and refrigerant
• It is also used as a solvent for some reactions.
• It is used in making wine.

Safety Measures:

Inhaling of sulphur dioxide causes some respiratory diseases and symptoms, which leads to difficulty in breathing and premature death. It also changes lung’s defences and causes some cardiovascular diseases. People who are suffering from asthma, lung or heart disease are much sensitive to sulphur dioxide. Sulphur dioxide not only affects human being but also it damages trees and crops along with oxides of nitrogen.  And, also causes the formation of microscopic aerosols of acid which have serious health implications.

Specific heat of liquid water

Introduction :

In 1819, Pierre-Louis Dulong and Alexis-Therese Petit, of France first defined specific heat.The heat capacity per unit mass of a body is called Specific heat.

Specific Heat Definition :
Specific heat is the quantity of heat required to alter the temperature by one degree of a unit mass of a substance.Specific heat capacity c, the heat capacity per unit mass, C= J/Kg. K

Specific Heat of Water

Specific heat of Water is high when compared to other liquids; and this helps water to stabilize temperatures.The specific heat of water = 4.184 Joules per gram per degree centigrade.

Image on Specific heat of liquid water

When water loses or absorbs a given amount of heat, there is a very slight change in its temperature because of the high specific heat of water as compared to other materials. When water is boiled in an iron pot, while the iron pot feels hot, the water in it is still lukewarm since the specific heat of water when compared to iron is ten times higher.

Reason for High Specific Heat of Water

Water’s high specific heat, is due to its hydrogen bonding. To make or break hydrogen bonds, heat is either released or absorbed. Water molecules move faster when heat is absorbed. Most of the heat energy is utilized to break up the hydrogen bond, hence there is comparatively less rise in the temperature of water.

Conclusion to Specific Heat of Liquid Water

Relevance of water’s high specific heat: Ocean temperatures remain stable, due to the high specific heat of water, thus supporting marine life. The ocean absorbs large amount of heat gradually from the sun during the day and releases this heat slowly at night. The air blowing over the land from the ocean gives a mild climate to coastal areas. Thus, water due to its high specific heat, maintains a stable environment on the earth for life to exist.

Heat Transfer System

Introduction :

Heat Transfer Definition :

Heat transfer is a process where heat is getting transferred from one place to another or heat exchange between two objects or its surroundings.

When ever a body is heated, heated the heat transfer takes place from that heated body to its surroundings or from heated part of the body to the cold part of the same body or heat transfer from hot body to water or air till the both body and the surrounding reach equilibrium.
Such spontanious heat transfer takes place on the second law of thermodynamics, that is always the heat transfer takes place from a reagion of higher temperature to the region of lower temperature.

                                                                                                                                                                                                    

Modes of Heat Transfer or Heat Tranfer Mechanism:

basically the transfer in three modes, that is

1. Conduction:

the conduction is a process where the heat is transfered between two solid materials in thermal contact, when ever one part of the body is heated the heat is transfered to the other reagion of the same part or the body which is in thermal contact with it through the atoms, in other words the heat transfer between the vibrating adjacent atoms is called Conduction.
steady state conduction is a process where the rate of heat entering into a body is equal to the rate of heat coming out of the body.

Convection and Radiation

Convection:

convection is a process of heat transfer where the heat is transferred through a fluid and gases. convection is mainly due to the heat transfer with the help of liquid and gases. here the heat transfer is mainly due to the flow of molecules in the fluid.
convection occurs due to newtons law of cooling, that is the rate of heat loss by a body is directly proportional to the difference in temperature between the body and the surrounding.

Radiation:

the process of heat transfer through the empty space by the help of electromagnetic waves is called radiation heat transfer. radiation does not require any medium for its process to happen, as it occurs with the help of electromagnetic waves radiation will occurrs in perfect vacuum.

by using the reflecting mirrors, the thermal radiation can be concentrated at a tiny part. the solar energy works with the help of this process.

Beryllium Atomic Mass

BERYLLIUM:

Beryllium is the element whose atomic number is 4. The beryllium is represented by the symbol Be. The various properties of beryllium are:

PHYSICAL PROPERTIES OF BERYLLIUM:

1. Beryllium exist in nature in solid phase.
2. The density of beryllium is 1.85 g/cm³
3. The melting point of beryllium is 1560 K
4. The boiling point of beryllium is 2742 K
5. The heat of vaporization of beryllium is 297 KJ/mol

CHEMICAL PROPERTIES OF BERYLLIUM:

1. Beryllium is present in various oxidation state like +2 and +1.
2. The electronegativity of beryllium is 1.57 in Pauling scale.
3. The ionization enthalpy of beryllium is as such:
1st ionization enthalpy: 899 KJ/mol
2nd ionization enthalpy: 1757 KJ/mol
3rd ionization enthalpy: 14848 KJ/mol
4. Beryllium is diamagnetic in nature.
5. The crystal structure of beryllium is hexagonal in shape.

Atomic Mass of Beryllium

The atomic mass of Beryllium is 9.01 g/mol. The atomic mass of Beryllium is the sum of the masses of all the electrons, protons and the neutrons. Since, there are 4 electrons present in one atom of Beryllium. Therefore, the number of protons are same in number that is 4 to neutralize the -ve charge of electrons. The rest mass addition is due to the presence of neutrons in the atom. The mass of each electron is 9.1x 10^-31 Kg. Mass of each proton is 1.67 x 10^-27 Kg. The mass of each neutron is 1.67 x 10^-27 Kg.
4 x 9.1 x 10^-31+ 4 x 1.67 x 10^-27 + 4 x 1.67 x 10^-27 Kg =  1.33636 x 10^-26 Kg = 9.01 g/mol.
The structure and this atomic mass makes the beryllium a useful element for the nuclear processes. The following two reactions shows the nuclear properties of Beryllium:
(1) 94Be + n → 2(42He) + 2n
Thsi reaction shows the the behaviour of beryllium to release more neutrons in respect to the number of neutrons absorbed by it.
(2)  94Be + 42He → 126C + n
This reaction shows the production of neutrons by hitting of Beryllium nuclei with alpha particles.

Uses of Beryllium

The various uses of beryllium are:
1. The use of beryllium is to tune the klystrons, magnetrons and travelling wave tubes.
2. Beryllium is used in nuclear weapon design.
3. It used for the manufacture of high frequency speaker drive.
4. It is used as a p-dopent semiconductor material in the electronic industry.
5. The compounds of beryllium are used in the flouroscent tube lights.