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.

Molar Heat of Vaporization of Water

Elements or compounds participate in reactions by means of their molecules and not atoms.This was postulated and proved by Avogadro.

The molecules are composed of atoms of same or different elements. In case of monatomic molecules of elements,there is no difference between the composition of molecule and atom.
The mass of the molecule is mass of constituent atoms which in turn is the mass of those atoms.
Therefore it can be said that the mass of a molecule is the sum of masses of protons and neutrons in the molecule.This is molar mass.The molar mass units is a.m.u.

What is the significance of the mass of the molecule and how is it related to mole or molar....?
A mole is molar mass expressed in terms of g.

It was proved by Avogadro that when the elements or compounds enter into a reaction,they do so not by their pure mass,but by the mass expressed in terms of grams.
e.g.

Formation of  ammonia
N₂ + 3H₂ ---------> 2NH₃
As mentioned above, it is not that 1g of nitrogen would combine with 3 g of hydrogen to form 2 g of ammonia.

However it is that 1mole of nitrogen would combine with 3 moles of hydrogen to form 2 moles of ammonia.
All the properties of compounds are related to moles or molar quantities.

Heat of Vaporization

Whenever a water is heated to a certain temperature, it undergoes two changes.

In the beginning the energy supplied is used to increase the energy of the molecules in the same liquid phase.The heat energy supplied from outside is utilised to increase the vibrating energy of the molecules which is noticed in form of rise in the temperature of the water.

In the second phase,the energy absorbed by the molecules, after reaching a threshold, no longer is used to increase the temperature but breaking the intermolecular attractions.

The intermolecular forces are overcome at a specific temperature which is called as boiling point.The liquid molecules which overcome these intermolecular forces turn into gas phase [steam].This process is called vaporization

The energy supplied beyond this boiling point is not utilized to increase the temperature but to overcome the intermolecular forces,by more and more number of molecules.As a result they vaporize accordingly.

When quantified, it was found that the energy required to vaporize a mole of water,called, molar heat of vaporization of water, is is 49.79 kJ/mole.
In other words,to vaporize one mole of water energy required is 49.79 kJ.

Atomic Mass of Iron

Iron is denoted by the symbol Fe. (Ferrum).    It belongs to Period 4 and Group 8 in the periodic table. It is grayish white in color with a specific gravity of 7.86.  Its atomic number is 26 and relative atomic mass is 55.85.  It exhibits variable valency  – 2 & 3.  

Introduction to atomic mass of iron

Atomic mass is the total number of neutrons and protons in the nucleus of the atom.  Atomic number is the total number of electrons or protons in an atom.  The electronic configuration is 2, 8, 14, 2.   The number of electrons in the atom is 26, which is equal to the number of protons. 

Atomic mass (A) = number of Protons (p) + number of Neutrons (n). 

Number of protons = number of electrons.

Atomic mass of iron = 26 + 29.85 = 55.85.

Atomic number of iron = 26

More about Atomic Mass of Iron

A close look at the electronic configuration of lighter elements reveals that those elements which had even number of protons, that is atomic number like 2He4, 6C12 etc. have their mass number twice their atomic number – except 4Be9 and 18Ar40.  Elements which have odd number of protons like 3Li7, 5B11 etc. have their mass number twice the atomic number + 1. (A = 2 Z +1) except 7 and 14 and 1H1.  This is not the case with heavier elements.  That is why iron, whose atomic mass is 26 does not have 52 as its mass number. 

Iron is not found in native state; it occurs only in combined state in its ore.  In this form, iron makes 5% of earth’s crust.  It is the second most abundant metal after aluminum.  

The ores of iron are red hematite (anhydrous ferric oxide) Fe2O3, brown hematite (hydrated ferric oxide) 2Fe2 O3. 3H2O, magnetite (triferric tetroxide) Fe3O4,  iron pyrites (iron disulphide) FeS2 and Siderite (ferrous carbonate) FeCO3. 

Iron is a heavy metal.  It is malleable and possesses high tensile strength.  It is a good conductor of heat and electricity.  It melts at 1535 degree Celsius.  It can be magnetized.