Chapter 01 | Introduction to Chemistry | Ninth Class Chemistry Notes
Chemistry
The branch of science which deals with the composition and properties of matter, changes in matter and the laws or principles which govern these changes is called Chemistry.
Branches of Chemistry
Physical Chemistry
The branch of chemistry which deals with the physical properties and physical behavior of material things is called physical chemistry.
The branch of chemistry which deals with the physical properties and physical behavior of material things is called physical chemistry.
Inorganic Chemistry
The study of all elements and their compounds except carbon is called inorganic chemistry.
The study of all elements and their compounds except carbon is called inorganic chemistry.
Organic Chemistry
The branch of chemistry in which we study the compounds of carbon is called organic chemistry.
The branch of chemistry in which we study the compounds of carbon is called organic chemistry.
Analytical Chemistry
The branch of chemistry which discusses the analytical methods for getting information about chemical compounds and chemical processes is called analytical chemistry.
The branch of chemistry which discusses the analytical methods for getting information about chemical compounds and chemical processes is called analytical chemistry.
Biochemistry
The study of chemical compounds present in living things is called biochemistry.
The study of chemical compounds present in living things is called biochemistry.
Industrial Chemistry
The application of chemical knowledge in technology and industry and the preparation of industrial products are called industrial chemistry.
The application of chemical knowledge in technology and industry and the preparation of industrial products are called industrial chemistry.
Steps Involved in Getting Information in the Scientific Method
Science is not only an integrated knowledge of physical and biological phenomena but also the methodology through which this knowledge is gathered. The process of scientific discoveries is a cyclic process.
In science the facts are gathered through observations and experiments and then theories or law are deduced. The scientific method include following four steps:
In science the facts are gathered through observations and experiments and then theories or law are deduced. The scientific method include following four steps:
1. Observation
2. Inference
3. Prediction
4. Experiment
2. Inference
3. Prediction
4. Experiment
1. Observation
The observations are made by the five senses of man. Men made equipments are also used for making observations. For example microscope is used for observing minute objects. Thermometer is used to measure temperature. Sensitive balance is used to determine the mass of a very light object. The capacity of man made instruments is also limited. But it can be improved by improving technology. Thus better and more reliable information are given to the scientists who produce better result. Information acquired through careful observations are called facts. These facts are foundation of scientific knowledge.
2. Inference
The facts gathered through observations are carefully arranged and properly classified. Correlating the knowledge thus acquired with previous knowledge, we try to think of a tentative solution to explain the observed phenomenon. The tentative solution is called hypothesis. The validity of this hypothesis is tested through the results obtained from experiments. The results are discussed by the scientists and the hypothesis is accepted or rejected. The accepted hypothesis then takes the form of theory. A theory when repeatedly gives the same results after experimentation and gives correct explanation of the scientific facts becomes a law or principle.
A theory remains valid until contrary informations are given on the basis of experimentation. Thus a hypothesis requires experimental support. But Avogadro’s hypothesis has been accepted as law without any experimental support.
A theory remains valid until contrary informations are given on the basis of experimentation. Thus a hypothesis requires experimental support. But Avogadro’s hypothesis has been accepted as law without any experimental support.
3. Prediction
Facts, theories and laws which are deduced from observation can help in deducing more facts and phenomenon. This process is called prediction.
4. Experiment
An experiment is an integrated activity, which is performed under suitable conditions with specially designed instruments to get the required information. Such information is used to test the validity of the hypothesis. If a hypothesis is proved correct. It increases the reliability of known facts. If it is proved wrong, it stil can give information which can be used to deduce other results.
Chemistry and Society
Chemistry has played important role for well being of mankind in the form of food, clothing, shelter, medical treatment and chemical fertilizers, crops protected by insecticides, refined food and production of artificial fiber. Production of cement, iron bricks, glass, paint etc are all due to chemistry.
The hazards of chemistry are so vast that no aspect of human life has remained unaffected. The smoke coming from chimneys of chemial industries and from vehicles pollute the air. It is very dangerous to breath in that air. Similarly waste water from industry, pollute canals, rivers and has bad effect on land. Excessive chemical spray on plants also has bad effect.
The hazards of chemistry are so vast that no aspect of human life has remained unaffected. The smoke coming from chimneys of chemial industries and from vehicles pollute the air. It is very dangerous to breath in that air. Similarly waste water from industry, pollute canals, rivers and has bad effect on land. Excessive chemical spray on plants also has bad effect.
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Chapter 02 | Chemical Combinations | Ninth Class Chemistry Notes
Laws of Chemical Combinations
There are four laws of chemical combinations these laws explained the general feature of chemical change. These laws are:
1. Law of Conservation of Mass
2. Law of Definite Proportions
3. Law of Multiple Proportions
4. Law Reciprocal Proportions
1. Law of Conservation of Mass
2. Law of Definite Proportions
3. Law of Multiple Proportions
4. Law Reciprocal Proportions
Antoine Lavoisier has rejected the worn out ideas about the changes that take place during a chemical reaction. He made careful quantitative measurements in chemical reactions and established that mass is neither created nor destroyed in a chemical change.
1. Law of Conservation of Mass
Statement
It is presented by Lavoisier. It is defined as:
It is presented by Lavoisier. It is defined as:
“Mass is neither created nor destroyed during a chemical reaction but it only changes from one form to another form.”
In a chemical reaction, reactants are converted to products. But the total mass of the reactants and products remains the same. The following experiment easily proves law of conservation of mass.
Practical Verification (Landolt Experiment)
German chemist H. Landolt, studied about fifteen different chemical reactions with a great skill, to test the validity of the law of conservation of mass. For this, he took H.shaped tube and filled the two limbs A and B, with silver nitrate (AgNO3) in limb A and Hydrochloric Acid (HCl) in limb B. The tube was sealed so that material could not escape outside. The tube was weighed initially in a vertical position so that the solution should not intermix with each other. The reactant were mixed by inverting and shaking the tube. The tube was weighed after mixing (on the formation of white precipitate of AgCl). He observed that weight remains same.
HCl + AgNO3 ———-> AgCl + NaNO3
German chemist H. Landolt, studied about fifteen different chemical reactions with a great skill, to test the validity of the law of conservation of mass. For this, he took H.shaped tube and filled the two limbs A and B, with silver nitrate (AgNO3) in limb A and Hydrochloric Acid (HCl) in limb B. The tube was sealed so that material could not escape outside. The tube was weighed initially in a vertical position so that the solution should not intermix with each other. The reactant were mixed by inverting and shaking the tube. The tube was weighed after mixing (on the formation of white precipitate of AgCl). He observed that weight remains same.
HCl + AgNO3 ———-> AgCl + NaNO3
2. Law of Definite Proportions
Statement
It is presented by Proust. It is defined as:
It is presented by Proust. It is defined as:
“When different elements combine to give a pure compound, the ratio between the masses of these elements will always remain the same.”
Proust proved experimentally that compound obtained from difference source will always contain same elements combined together in fixed proportions.
Example
Water can be obtained from different sources such as river, ocean, well, canal, tube well, rain or by the chemical combination of hydrogen and oxygen. If different samples of water are analyzed, it will have two elements, hydrogen and oxygen and the ratio between their mass is 1:8.
Water can be obtained from different sources such as river, ocean, well, canal, tube well, rain or by the chemical combination of hydrogen and oxygen. If different samples of water are analyzed, it will have two elements, hydrogen and oxygen and the ratio between their mass is 1:8.
3. Law of Multiple Proportions
Statement
This law is defined as:
This law is defined as:
“When two elements combine to give more than one compounds, the different masses of one element, which will combine with the fixed mass of other element, will be in simple whole number ratio.”
Two different elements can combine to form more than one compound. They can do so by combining in different ratios to give different compounds.
Example
Hydrogen and oxygen combine with one another to form water (H2O) and hydrogen peroxide (H2O2). In water and hydrogen oxide 2 g of hydrogen combine with 16g and 32g of oxygen respectively. According to law of multiple proportions, the different masses of oxygen (16g and 32g) which have reacted with fixed mass (2g) of hydrogen will have a simple ratio between each other i.e. 16:32 or 1:2. It means that hydrogen peroxide contains double the number of oxygen atoms than water. This law proves this point of Dalton’s Atomic Theory that atoms do not break in a chemical reaction.
Hydrogen and oxygen combine with one another to form water (H2O) and hydrogen peroxide (H2O2). In water and hydrogen oxide 2 g of hydrogen combine with 16g and 32g of oxygen respectively. According to law of multiple proportions, the different masses of oxygen (16g and 32g) which have reacted with fixed mass (2g) of hydrogen will have a simple ratio between each other i.e. 16:32 or 1:2. It means that hydrogen peroxide contains double the number of oxygen atoms than water. This law proves this point of Dalton’s Atomic Theory that atoms do not break in a chemical reaction.
4. Law of Reciprocal Proportions
Statement
This law is defined as:
This law is defined as:
“When two element A, B combine separately, with the mixed mass of the third element E, the ratio in which these elements combine with E is either the same or simple multiple of the ratio in which A and B combine with each other.”
Example
Hydrogen and Nitrogen separately combine to form ammonia (NH3) and dinitrogen oxide (N2O), in these compounds, fixed mass of nitrogen is 14g and combines with 8 g of oxygen and 3 g of hydrogen. The ratio between the mass of oxygen and hydrogen is 8:3. Hydrogen and oxygen also combine with one another to form water (H2O). The ratio between hydrogen and oxygen in water is 16:2. These ratios are not same. Let us observe whether these ratios are simple multiple to each other or not following mathematical operation is carried out.
8:3 ::16:2
8/3 : 16/2
or
8/3 x 2/16
or
1/3 => 1:3
Hydrogen and Nitrogen separately combine to form ammonia (NH3) and dinitrogen oxide (N2O), in these compounds, fixed mass of nitrogen is 14g and combines with 8 g of oxygen and 3 g of hydrogen. The ratio between the mass of oxygen and hydrogen is 8:3. Hydrogen and oxygen also combine with one another to form water (H2O). The ratio between hydrogen and oxygen in water is 16:2. These ratios are not same. Let us observe whether these ratios are simple multiple to each other or not following mathematical operation is carried out.
8:3 ::16:2
8/3 : 16/2
or
8/3 x 2/16
or
1/3 => 1:3
Definitions
Atomic Mass
The mass of an atom of the element relative to the mass of some reference or standard element is called atomic mass. Atoms are very small particles. They have very small mass. If the masses of atoms were to be expressed in gram. It is a very big unit for this very tiny object. Then it was decided by the chemists that masses of the atoms were to be found after comparing with mass to some standard form.
Hydrogen being the lightest element is taken as standard. The mass of the hydrogen atom taken as one.
The atomic mass could be defined as
Hydrogen being the lightest element is taken as standard. The mass of the hydrogen atom taken as one.
The atomic mass could be defined as
“Atomic mass of an element is the mass of an atom of that element as compared to the mass of an atom of hydrogen taken as one.”
Example
The atomic mass of sodium is 23. It means that an atom of sodium is 23 times heavier than hydrogen atom. Similarly atomic mass of oxygen is 16. It means that an atom of oxygen is 16 times heaviest than that of hydrogen.
The atomic mass of sodium is 23. It means that an atom of sodium is 23 times heavier than hydrogen atom. Similarly atomic mass of oxygen is 16. It means that an atom of oxygen is 16 times heaviest than that of hydrogen.
Atom
The smallest particle of an element which cannot exist independently and take part in a chemical reaction is known as Atom.
Examples
Hexogen(H), Carbon (C), Sodium (Na), Gold (Au) etc.
Hexogen(H), Carbon (C), Sodium (Na), Gold (Au) etc.
Molecule
The particle of a substance (Element or Compound) which can exist independently and show all the properties of that substance is called molecule.
Atoms of the same or different elements react with each other and form molecule.
Atoms of some elements can exist independently, since they have property of molecule so they are called mono atomic molecule.
Atoms of some elements can exist independently, since they have property of molecule so they are called mono atomic molecule.
Examples
Examples of Molecules of the elements are Hydrogen (H2). Nitrogen (N2), Sulphur (S8) etc.
Molecules of different elements are called compounds. For example HCl, H2O, CH4 etc.
Examples of Molecules of the elements are Hydrogen (H2). Nitrogen (N2), Sulphur (S8) etc.
Molecules of different elements are called compounds. For example HCl, H2O, CH4 etc.
Valency
The combining capacity of all elements with other elements is called valency.
Example
H = 1
C = 4
Al = 3
Mg = 2
Na = 1
H = 1
C = 4
Al = 3
Mg = 2
Na = 1
Chemical Formula
“A brief name used for full chemical name at a compound is called Chemical Formula.”
A chemical formula is used to represent an element or a compound in terms of symbols. It also represents the number and type of atoms of elements present in the smallest unit of that substance.
Example
The chemical formula of hydrogen sulphide is H2S. It shows two types of elements (H and S) and number of atoms of element (2H and 1S). Similarly the formula of NaCl show number and type of different atoms present in its smallest unit.
The chemical formula of hydrogen sulphide is H2S. It shows two types of elements (H and S) and number of atoms of element (2H and 1S). Similarly the formula of NaCl show number and type of different atoms present in its smallest unit.
Empirical Formula
“The formula which shows the minimum (simple) ratio between atoms present in a compound is known as Empirical Formula.”
Example
For example the empirical formula of hydrogen peroxide is HO that of water is H2O and benzene is CH.
For example the empirical formula of hydrogen peroxide is HO that of water is H2O and benzene is CH.
Molecular Formula
The formula of an element or a compound which represents the actual number of atoms present in the molecule of these substances is called molecular formula.
Example
Water, Hydrogen Peroxide, Ethylene Benzene and Sulphur have molecular formula H2O, H2O2, C2H4, C6H6 and S8 respectively.
Water, Hydrogen Peroxide, Ethylene Benzene and Sulphur have molecular formula H2O, H2O2, C2H4, C6H6 and S8 respectively.
Molecular Mass
Molecular mass of an element or a compound is defined as the mass of its molecule relative to 1/12th of the mass of C-12. It is the sum of the atomic masses of all the atoms presents in its molecular formula.
Example
Molecular mass of water (H2O) = 2 + 16 = 18 a.m.u
Mass of hydrogen sulphide (H2S) = 2 + 32 = 34 a.m.u
Molecular mass of water (H2O) = 2 + 16 = 18 a.m.u
Mass of hydrogen sulphide (H2S) = 2 + 32 = 34 a.m.u
Formula Mass
Formula mass of a compound is the mass of its formula unit relative to 1/12th of the mass of C-12.
Example
Formula mass of Sodium Chloride NaCl = 23 + 35.5 = 58.5 a.m.u
Formula mass of Calcium Chloride CaCl2 = 40 + 35.5×2 = 111a.m.u
Formula mass of Sodium Chloride NaCl = 23 + 35.5 = 58.5 a.m.u
Formula mass of Calcium Chloride CaCl2 = 40 + 35.5×2 = 111a.m.u
Molar Mass
The mass of one mole of a substance is called molar mass.
Example
1 mole of Hydrogen atom (H) = 1.008g
1 mole of Hydrogen molecule (H2) = 2.016g
Thus mass of substance is related to the particles by mole.
1 mole of Hydrogen atom (H) = 1.008g
1 mole of Hydrogen molecule (H2) = 2.016g
Thus mass of substance is related to the particles by mole.
Chemical Reaction
A chemical change in which reactants are converted to products is called chemical reaction.
Zn + 2HCl ——–> ZnCl2 + H2
The fact that a chemical reaction is taking place can be inferred from the following observation.
1. Evolution of a gas
2. Change in colour
3. Change in temperature.
4. Emission of light.
Zn + 2HCl ——–> ZnCl2 + H2
The fact that a chemical reaction is taking place can be inferred from the following observation.
1. Evolution of a gas
2. Change in colour
3. Change in temperature.
4. Emission of light.
Types of Chemical Reaction
The chemical reaction is classified into following types:
1. Displacement Reaction
The reaction in which an atom or group of atoms is displaced by another atom or group of atoms in a compound is called displacement reaction.
Fe + CuO ———> Cu + FeO
The reaction in which an atom or group of atoms is displaced by another atom or group of atoms in a compound is called displacement reaction.
Fe + CuO ———> Cu + FeO
2. Double Displacement Reactions
The reactions in which reacting substances exchange their radicals or ions are double displacement reaction. Insoluble salts are formed by mixing soluble salts.
The reactions in which reacting substances exchange their radicals or ions are double displacement reaction. Insoluble salts are formed by mixing soluble salts.
3. Addition Reactions
When two different compounds or elements react together to give only one confound, the reaction will be called addition reaction.
2Mg + O2 ——–> 2MgO
When two different compounds or elements react together to give only one confound, the reaction will be called addition reaction.
2Mg + O2 ——–> 2MgO
4. Decomposition Reaction
The reaction in which some compounds may decompose into elements or simpler compounds on heating is called decomposition reaction.
CaCO3 ———> CaO + CO2 (Heat)
The reaction in which some compounds may decompose into elements or simpler compounds on heating is called decomposition reaction.
CaCO3 ———> CaO + CO2 (Heat)
Chemical Equation
Symbolic representation of chemical change in terms of symbols and formulae is called Chemical Equation.
Method of Equation Writing
A chemical equation can be written as follows:
1. Write the formulae and symbols of the reactants on the left hand side.
2. Write the formulae and sympols of the products on the right hand side.
3. Separate the reactants and products by an arrow which is directed towards the products.
1. Write the formulae and symbols of the reactants on the left hand side.
2. Write the formulae and sympols of the products on the right hand side.
3. Separate the reactants and products by an arrow which is directed towards the products.
Characteristics of Chemical Equation
1. Chemical equation must be representative of a chemical reaction.
2. It should represent molar quantities.
3. It should be balanced in terms of atoms/molecules of reactants and products.
2. It should represent molar quantities.
3. It should be balanced in terms of atoms/molecules of reactants and products.
Reactants
Those substances, which react together in a chemical reaction, are called reactants.
Zn + 2HCl ——> ZnCl2 + H2
In the above reaction Zn and HCl are the reactants.
Zn + 2HCl ——> ZnCl2 + H2
In the above reaction Zn and HCl are the reactants.
Products
Those substances, which are formed in a chemical reaction, are called products.
Zn + 2HCl ——> ZnCl2 + H2
In the above reaction, ZnCl2 and H2 are products.
Information obtained from a Chemical Equation
Zn + 2HCl ——> ZnCl2 + H2
In the above reaction, ZnCl2 and H2 are products.
Information obtained from a Chemical Equation
1. A balanced equation indicates that which reactant undergo chemical change. It indicates that which products are formed.
2. It indicates that how many moles of reactants under go chemical change. It indicates that how many moles of products are formed.
2. It indicates that how many moles of reactants under go chemical change. It indicates that how many moles of products are formed.
Why are Chemical Equations Balanced
A chemical equation must be balanced in order to satisfy the law of conservation of matter, which states that matter can neither be created nor be destroyed during a chemical reaction.
Chapter 03 | Atomic Structure | Ninth Class Chemistry Notes
Dalton’s Atomic Theory
The important postulates of Dalton’s atomic theory are:
1. All elements are composed of atoms. Atom is too small so that it could not be divided into further simpler components.
2. Atom cannot be destroyed or produced.
3. Atoms of an element are similar in all respects. They have same mass and properties.
4. Atoms of different elements combine in a definite simple ratio to produce compounds.
1. All elements are composed of atoms. Atom is too small so that it could not be divided into further simpler components.
2. Atom cannot be destroyed or produced.
3. Atoms of an element are similar in all respects. They have same mass and properties.
4. Atoms of different elements combine in a definite simple ratio to produce compounds.
Discovery of Electron
A discharge tube is a glass tube. It has two electrode, a source of electric current and a vacuum pump.
(Diagram)
Sir William Crooks (1895 performed experiments by passing electric current through gas in the discharge tube at very low pressure. He observed that at 10-4 (-4 is power to 10) atmosphere pressure, shining rays are emitted from cathode. These rays were named cathode rays. Cathode rays are material particles as they have mass and momentum.
(Diagram)
Sir William Crooks (1895 performed experiments by passing electric current through gas in the discharge tube at very low pressure. He observed that at 10-4 (-4 is power to 10) atmosphere pressure, shining rays are emitted from cathode. These rays were named cathode rays. Cathode rays are material particles as they have mass and momentum.
Properties of Cathode Rays
The properties of these particles are given below:
1. These particles are emitted from cathode surface and move in straight line.
2. The temperature of the object rises on which they fall.
3. They produce shadow of opaque object placed in their path.
4. These particles are deflected in electric and magnetic fields.
5. These particles are deflected towards positive plate of electric field.
2. The temperature of the object rises on which they fall.
3. They produce shadow of opaque object placed in their path.
4. These particles are deflected in electric and magnetic fields.
5. These particles are deflected towards positive plate of electric field.
Discovery of Proton
Gold Stein (1886) observed that in addition to the cathode rays, another type of rays were present in the discharge tube. These rays travel in a direction opposite to cathode rays. These rays were named positive rays. By using perforated cathode in the discharge tube the properties of these rays can be studied. Positive rays are also composed of metered particles. The positive rays are not emitted from anode. They are produced by the ionization of residual gas molecules in the discharge tube. When cathode rays strike with gas molecule, electrons are removed and positive particles are produced.
Properties of Positive Rays
1. They are deflected towards negative plate of electric field. Therefore these rays carry positive charge.
2. The mass of positive rays is equal to the mass of the gas enclosed in the discharge tube.
3. The minimum mass of positive particles is equal to the mass of hydrogen ion (H+). These positive ions are called Protons.
4. The charge on proton is equal to +1.602×10-19 Coulomb. (-19 is power of 10)
3. The minimum mass of positive particles is equal to the mass of hydrogen ion (H+). These positive ions are called Protons.
4. The charge on proton is equal to +1.602×10-19 Coulomb. (-19 is power of 10)
Natural Radioactivity
The phenomenon in which certain elements emit radiation which can cause fogging of photographic plate is called natural radioactivity. The elements which omit these rays are called radioactive elements like Uranium, Thorium, Radium etc. There are about 40 radioactive elements. Henri Bequrel (1896) discovered radioactivity.Madam Curei also has valuable contribution in this field.
In natural radioactivity nuclei of elements are broken and element converted to other elements. Natural radioactivity is nuclear property of the elements.
In natural radioactivity nuclei of elements are broken and element converted to other elements. Natural radioactivity is nuclear property of the elements.
Alpha Rays
1. They are helium nuclei. They are doubly positively charged, He2+.
2. They move with speed equal to the 1/10th of the velocity of the light.
3. They cannot pass through thick-metal foil.
4. They are very good ionizer of a gas.
5. They affect the photographic plate.
3. They cannot pass through thick-metal foil.
4. They are very good ionizer of a gas.
5. They affect the photographic plate.
Beta Rays
1. They are negatively charged.
2. They move with the speed equal to the velocity of light.
3. They can pass through a few millimeter thick metal sheets.
4. They are good ionizer of a gas.
5. They can affect the photographic plate.
2. They move with the speed equal to the velocity of light.
3. They can pass through a few millimeter thick metal sheets.
4. They are good ionizer of a gas.
5. They can affect the photographic plate.
Gamma Rays
1. They are electromagnetic radiations.
2. They travel with speed equal to velocity of light.
3. They carry no charge.
4. They have high penetration power than alpha and beta rays.
5. They are weak ionizer of gas.
2. They travel with speed equal to velocity of light.
3. They carry no charge.
4. They have high penetration power than alpha and beta rays.
5. They are weak ionizer of gas.
Rutherford Experiment and Discovery of Nucleus
Lord Rutherford (1911) and his coworkers performed an experiment. They bombarded a very thin, gold fail with Alpha particles from a radioactive source. They observed that most of the particles passed straight through the foil undeflected. But a few particles were deflected at different angles. One out of 4000 Alpha particles was deflected at an angle greater than 150.
(Diagram)
(Diagram)
Conclusion
Following conclusions were drawn from the Rutherford’s Alpha Particles scattering experiment.
1. The fact that majority of the particles went through the foil undeflected shows that most of the space occupied by an atom is empty.
2. The deflection of a few particles over a wide angle of 150 degrees shows that these particles strike with heavy body having positive charge.
3. The heavy positively charged central part of the atom is called nucleus.
4. Nearly all of the mass of atom is concentrated in the nucleus.
5. The size of the nucleus is very small as compared with the size of atom.
1. The fact that majority of the particles went through the foil undeflected shows that most of the space occupied by an atom is empty.
2. The deflection of a few particles over a wide angle of 150 degrees shows that these particles strike with heavy body having positive charge.
3. The heavy positively charged central part of the atom is called nucleus.
4. Nearly all of the mass of atom is concentrated in the nucleus.
5. The size of the nucleus is very small as compared with the size of atom.
Defects of Rutherford Model
Rutherford model of an atom resembles our solar system. It has following defects:
1. According to classical electromagnetic theory, electron being charged body will emit energy continuously. Thus the orbit of the revolving electron becomes smaller and smaller until it would fall into the nucleus and atomic structure would collapse.
2. If revolving electron emits energy continuously then there should be a continuous spectrum but a line spectrum is obtained.
(Diagram)
1. According to classical electromagnetic theory, electron being charged body will emit energy continuously. Thus the orbit of the revolving electron becomes smaller and smaller until it would fall into the nucleus and atomic structure would collapse.
2. If revolving electron emits energy continuously then there should be a continuous spectrum but a line spectrum is obtained.
(Diagram)
Bohr’s Atomic Model
Neil Bohr (1913) presented a model of atom which has removed the defects of Rutherford Model. This model was developed for hydrogen atom which has only proton in the nucleus and one electron is revolving around it.
Postulates of Bohr’s Atomic Model
The main postulates of Bohr’s Model are given below:
1. Electrons revolve around the nucleus in a fixed orbit.
2. As long as electron revolves in a fixed orbit it does not emit and absorb energy. Hence energy of electron remains constant.
3. The orbit nearest to the nucleus is the first orbit and has lowest energy. When an electron absorbs energy it jumps from lower energy orbit to higher energy orbit. Energy is emitted in the form of radiations, when an electron jumps from higher energy orbit to lower energy orbit. The unit of energy emitted in the form of radiations is called quantum. It explains the formation of atomic spectrum.
4. The change in energy is related with the quantum of radiation by the equation :
E2 – E1 = hv
where
E1 = Energy of first orbit
E2 = Energy of the second orbit
h = Planck’s constant
v = Frequency of radiation
1. Electrons revolve around the nucleus in a fixed orbit.
2. As long as electron revolves in a fixed orbit it does not emit and absorb energy. Hence energy of electron remains constant.
3. The orbit nearest to the nucleus is the first orbit and has lowest energy. When an electron absorbs energy it jumps from lower energy orbit to higher energy orbit. Energy is emitted in the form of radiations, when an electron jumps from higher energy orbit to lower energy orbit. The unit of energy emitted in the form of radiations is called quantum. It explains the formation of atomic spectrum.
4. The change in energy is related with the quantum of radiation by the equation :
E2 – E1 = hv
where
E1 = Energy of first orbit
E2 = Energy of the second orbit
h = Planck’s constant
v = Frequency of radiation
Atomic Number
The number of protons present in the nucleus of an atom is called atomic number or proton number. It is denoted by z. The proton in the nucleus of an atom is equal to number of electrons revolving around its nucleus.
Mass Number
The total number of the protons and neutrons present in the nucleus of an atom is called mass number. The protons and neutrons together are called nucleon. Hence it is also known as nucleon number. It is denoted by A. the number of neutrons present in the nucleus of an atom is rperesented by N.
Mass Number = No of Protons + No of neutrons
A = Z + N
Mass Number = No of Protons + No of neutrons
A = Z + N
Isotopes
The atoms of same elements which have same atomic number but different mas number are called Isotopes. The number of protons present in the nucleus of an atom remains the same but number of neutrons may differ.
Isotopes of Different Elements
Isotopes of Different Elements
Isotopes of Hydrogen
Hydrogen has three isotopes:
1. Ordinary Hydrogen or Protium, H.
2. Heavy Hydrogen or Deutrium, D.
3. Radioactive Hydrogen or Tritium, T.
Hydrogen has three isotopes:
1. Ordinary Hydrogen or Protium, H.
2. Heavy Hydrogen or Deutrium, D.
3. Radioactive Hydrogen or Tritium, T.
Protium
Ordinary naturally occurring hydrogen contains the largest percentage of protium. It is denoted by symbol H. It has one proton in its nucleus and one electron revolve around the nucleus.
Number of Protons = 1
Number of Electrons = 1
Number of Neutrons = 0
Atomic Number = 1
Mass Number = 1
Ordinary naturally occurring hydrogen contains the largest percentage of protium. It is denoted by symbol H. It has one proton in its nucleus and one electron revolve around the nucleus.
Number of Protons = 1
Number of Electrons = 1
Number of Neutrons = 0
Atomic Number = 1
Mass Number = 1
Deutrium
Deutrium is called heavy hydrogen. The percentage of deutrium in naturally occuring hydrogen is about 0.0015%. It has one proton and one neutron in its nucleus. It has one electron revolving around its nucleus. It is denoted by symbol D.
Number of Proton = 1
Number of Electron = 1
Number of Neutrons = 1
Atomic Number = 1
Mass Number = 2
Deutrium is called heavy hydrogen. The percentage of deutrium in naturally occuring hydrogen is about 0.0015%. It has one proton and one neutron in its nucleus. It has one electron revolving around its nucleus. It is denoted by symbol D.
Number of Proton = 1
Number of Electron = 1
Number of Neutrons = 1
Atomic Number = 1
Mass Number = 2
Tritium
Radioactive hydrogen is called tritium. It is denoted by symbol T. The number of tritium isotope is one in ten millions. It has one proton and 2 neutrons in its nucleus. It has one electron revolving around its nucleus.
Number of Proton = 1
Number of Electron = 1
Number of Neutron = 2
Atomic Number = 1
Mass Number = 3
Radioactive hydrogen is called tritium. It is denoted by symbol T. The number of tritium isotope is one in ten millions. It has one proton and 2 neutrons in its nucleus. It has one electron revolving around its nucleus.
Number of Proton = 1
Number of Electron = 1
Number of Neutron = 2
Atomic Number = 1
Mass Number = 3
Chapter 04 | Periodicity of Elements | Ninth Class Chemistry Notes
Definitions
Periodic Table
A table of elements obtained by arranging them in order of their increasing atomic number in which elements having similar properties are placed in the same group is called Periodic Table.
Group
The vertical column of elements in the periodic table are called Groups.
Period
The horizontal rows of elements in the periodic table are called Periods.
Periodicity
The repetition of physical and chemical properties of elements periodically is called Periodicity of Properties.
Periodic Law
Physical and chemical properties of elements are periodic function of their atomic masses.
Metal
Elements which are good conductors of heat and electricity are malleable and ductile and have a metallic luster are called Metals like Sodium, Potassium, Gold, Copper etc.
Non-Metals
Elements which are non or bad conductor of heat and electricity are neither malleable or ductile and have no metallic luster are called Non-Metals like Carbon, Nitrogen, Chlorine etc.
Metalloids
Metalloids are semi metals have the properties which are intermediate between a metal and non-metal like Boron, Silicon, Germanium, Arsenic, Antimony etc.
Law of Triads
A German Chemist, Dobereiner (1829), arranged chemically similar elements in groups of three on the basis of their atomic masses called Triads and it was found that atomic mass of the middle element was approximately equal to the average of atomic masses of other two elements. This is known as Law of Triads.
Drawback or Defect
As very few elements could be arranged in such groups, this classification did not get wide acceptance.
Law of Octaves
An English Chemist Newland (1864) stated that if the elements were arranged in the ascending order of their atomic masses, every eight element will have similar properties to the first. This is knows as Law of Octaves.
Drawback or Defects
1. Noble gases were not discovered at that time and no place was reserved for the undiscovered noble gases.
2. In the same way no blank spaces for the undiscovered elements were present in his table.
2. In the same way no blank spaces for the undiscovered elements were present in his table.
Mendeleyv’s Period Table and Periodic Law
Russian Chemist, Mendeleyv’s (186) who wa working separately from Lother Mayer published a table of elements.
According to Mendeleyv’s when the element were arranged in order of their increasing atomic mases, the elements with similar properties were repeated after regular interval and were placed one above the other.A table obtained in this manner is called Periodic Table. Mendeleyv’s stated this periodicity in the form of Periodic Law.
According to Mendeleyv’s when the element were arranged in order of their increasing atomic mases, the elements with similar properties were repeated after regular interval and were placed one above the other.A table obtained in this manner is called Periodic Table. Mendeleyv’s stated this periodicity in the form of Periodic Law.
Important Features of Mendeleyv’s Periodic Table
The important features of Mendeleyv’s Periodic table are:
Periods and Groups
The horizontal rows which run from left to right in Periodic Table are called Periods and they are twelve in number.
The vertical rows which run from top to bottom in periodic table are called groups and they are eight in number.
The horizontal rows which run from left to right in Periodic Table are called Periods and they are twelve in number.
The vertical rows which run from top to bottom in periodic table are called groups and they are eight in number.
Vacant Spaces
Mendeleyv’s left many vacant spaces for the still unknown elements. For example, next to Calcium (40) should be Titanium (48) but it resembled silicon (28) instead of Aluminium (27). He left vacant space for element with atomic mass 44.
Mendeleyv’s left many vacant spaces for the still unknown elements. For example, next to Calcium (40) should be Titanium (48) but it resembled silicon (28) instead of Aluminium (27). He left vacant space for element with atomic mass 44.
Discovery of New Element
Mendeleyv’s discovered new elements and also guessed their atomic mass and properties.
Mendeleyv’s discovered new elements and also guessed their atomic mass and properties.
Atomic Mass Correction
Mendeleyv’s corrected the atomic masses of certain elements on basis of their properties and provided proper place to them in the periodic table.
Mendeleyv’s corrected the atomic masses of certain elements on basis of their properties and provided proper place to them in the periodic table.
Defects in Mendeleyv’s Periodic Table
The Mendeleyv’s Period Table has following defects:
Irregular Position of Some Elements
According to Mendeleyv’s Periodic Law Potassium (39) should be placed before Argon (40) but he placed Argon (40) before Potassium (39) which goes against his law.
According to Mendeleyv’s Periodic Law Potassium (39) should be placed before Argon (40) but he placed Argon (40) before Potassium (39) which goes against his law.
Position of Isotopes
Mendeleyv’s periodic table gives no indication about the position of isotopes.
Mendeleyv’s periodic table gives no indication about the position of isotopes.
Structure of Atom
Mendeleyv’s Periodic table gives no idea about structure of atoms.
Mendeleyv’s Periodic table gives no idea about structure of atoms.
Position of Lanthanides and Actinides
Lanthanides and Actinides have not been given proper place in Periodic Table.
Lanthanides and Actinides have not been given proper place in Periodic Table.
Coinage and Alkali Metals
Alkali metals and coinage metals with different properties are placed in the same group. This defect has been replaced by placing them into two sub groups.
Alkali metals and coinage metals with different properties are placed in the same group. This defect has been replaced by placing them into two sub groups.
Modern Periodic Law and Modern Periodic Table
Modern Periodic Law
Physical and chemical properties of the elements are periodic function of their atomic number. Mosely (1913) says that atomic mas is not fundamental property. Due to some defects present in Mendeleyv’s periodic law, Mosely introduced the concept of anomic number for the elements.
Physical and chemical properties of the elements are periodic function of their atomic number. Mosely (1913) says that atomic mas is not fundamental property. Due to some defects present in Mendeleyv’s periodic law, Mosely introduced the concept of anomic number for the elements.
Example
When isotopes were discovered, it was thought advisable to arrange the elements on basis of their atomic number instead o increasing atomic mases. Isotopes were needed different position in the Mendeleyv’s periodic table. Hence Mendeleyv’s periodic law was modified.
When isotopes were discovered, it was thought advisable to arrange the elements on basis of their atomic number instead o increasing atomic mases. Isotopes were needed different position in the Mendeleyv’s periodic table. Hence Mendeleyv’s periodic law was modified.
Modern Periodic Table
When Mendeleyv’s periodic law was modified and new elements were discovered. This forcd the scientists to change Mendeleyv’s periodic law.
The electronic configuration of atoms also played an important role in he arrangement of the modern periodic law. This form of periodic table is called “Long form of Periodic Table” because it contains eighteen groups instead of eight but seven periods instead of twelve.
When Mendeleyv’s periodic law was modified and new elements were discovered. This forcd the scientists to change Mendeleyv’s periodic law.
The electronic configuration of atoms also played an important role in he arrangement of the modern periodic law. This form of periodic table is called “Long form of Periodic Table” because it contains eighteen groups instead of eight but seven periods instead of twelve.
Group I – The Alkali Metals
The elements of group I are called “Alkali Metals”. The word alkali is derived from an Arabic word meaning Ashes.
Elements of Group I
Lithium
Sodium
Potassium
Rubidium
Cesium
Francium
Lithium
Sodium
Potassium
Rubidium
Cesium
Francium
Properties of Group I
1. They are mono atomic.
2. They exist in solid metallic state.
3. Outer most shell of these elements is incomplete having one electron.
4. Elements of this group are highly reactive.
5. Elements of this group have large tendency to form compounds.
6. Elements of this group are strongly electro-positive.
1. They are mono atomic.
2. They exist in solid metallic state.
3. Outer most shell of these elements is incomplete having one electron.
4. Elements of this group are highly reactive.
5. Elements of this group have large tendency to form compounds.
6. Elements of this group are strongly electro-positive.
Group II – The Alkaline Earth Metals
The elements of group II are called Alkaline Earth Metals. These elements occur in nature as silicate mineral and their oxides and hydroxides are strongly basic. Therefore these elements are called Alkaline Earth Metals.
Elements of Group II
Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
Beryllium
Magnesium
Calcium
Strontium
Barium
Radium
Properties of Group II
1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having two electrons.
4. Elements of this group are moderately reactive.
5. Elements of this group have moderate tendency to form compounds.
1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having two electrons.
4. Elements of this group are moderately reactive.
5. Elements of this group have moderate tendency to form compounds.
Group III – The Boron or Aluminium Family
The elements of group III exist in solid state.
Elements of Group III
Boron Metalloid
Aluminium Metal
Gallium Metal
Indium Metal
Thallium Metal
Boron Metalloid
Aluminium Metal
Gallium Metal
Indium Metal
Thallium Metal
Properties of Group III
1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having three electrons.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.
1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having three electrons.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.
Group IV – The Carbon and Silicon Family
Elements of Group IV
Carbon
Silicon
Germanium
Tin
Lead
Carbon
Silicon
Germanium
Tin
Lead
Properties of Group IV
1. They are mono atomic.
2. They exist in solid state.
3. Outermost shell of these elements is incomplete.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.
1. They are mono atomic.
2. They exist in solid state.
3. Outermost shell of these elements is incomplete.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.
Group V – The Nitrogen Family
Elements of Group V
Nitrogen
Phosphorus
Arsenic
Antimony
Bismuth
Nitrogen
Phosphorus
Arsenic
Antimony
Bismuth
Properties of Group V
1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Outermost shell of these elements is incomplete having five electrons.
4. elements of this group are quite reactive.
5. Elements of this group have quite tendency to form compound.
1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Outermost shell of these elements is incomplete having five electrons.
4. elements of this group are quite reactive.
5. Elements of this group have quite tendency to form compound.
Group VI – The Oxygen Family
Elements of Group VI
Oxygen
Sulphur
Selenium
Tellurium
Polonium
Oxygen
Sulphur
Selenium
Tellurium
Polonium
Properties of Group VI
1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Elements of this group have quite tendency to form compounds.
4. The tendency of forming covalent bond decreases from oxygen to polonium.
5. There is a gradual decrease in the ionization potential down the group.
1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Elements of this group have quite tendency to form compounds.
4. The tendency of forming covalent bond decreases from oxygen to polonium.
5. There is a gradual decrease in the ionization potential down the group.
Group VII – The Halogen Family
Elements of Group VII
Fluorine Gas
Chlorine Gas
Bromine Liquid
Iodine Solid
Astatine Radioactive
Fluorine Gas
Chlorine Gas
Bromine Liquid
Iodine Solid
Astatine Radioactive
Properties of Group VII
1. They are diatomic except At.
2. Halogens are very active non-metals.
3. Outer most shell of these elements is incomplete having seven electrons.
4. Elements of this group are highly reactive.
5. There is a gradual decrease in the ionization potential down the
1. They are diatomic except At.
2. Halogens are very active non-metals.
3. Outer most shell of these elements is incomplete having seven electrons.
4. Elements of this group are highly reactive.
5. There is a gradual decrease in the ionization potential down the
group.
Transition Elements
Definition
Elements in Group IB, IIB, through VIIB are known as Transition Elements because they show their properties which are transitional between higly reactive and strong electro-positive elements of S-block which form ionic compounds and p-block elements which form largely covalent compounds.
Elements in Group IB, IIB, through VIIB are known as Transition Elements because they show their properties which are transitional between higly reactive and strong electro-positive elements of S-block which form ionic compounds and p-block elements which form largely covalent compounds.
Properties of Transition Elements
1. Transition Elements have incomplete inner electron shells.
2. They show variable valency.
3. They show similar behaviour.
4. They all are metals.
5. They have strong inner atomic bonds.
1. Transition Elements have incomplete inner electron shells.
2. They show variable valency.
3. They show similar behaviour.
4. They all are metals.
5. They have strong inner atomic bonds.
Group 0, The Noble Gases
The elements of Group VIII A are called “Noble Gases” or “Inert Gases” or “Zero Group Elements”.
Elements of Group 0
Helium
Neon
Argon
Krypton
Xenon
Radon
Helium
Neon
Argon
Krypton
Xenon
Radon
Properties of Group 0
1. They are mono atomic.
2. They exist in gaseous state.
3. Outer most shell of these elements is either complete or contains eight electrons.
4. These elements are mostly chemically non-reactive.
5. These elements have no tendency to form compounds (only a few of these compounds are known).
1. They are mono atomic.
2. They exist in gaseous state.
3. Outer most shell of these elements is either complete or contains eight electrons.
4. These elements are mostly chemically non-reactive.
5. These elements have no tendency to form compounds (only a few of these compounds are known).
Atomic Radius
Definition
One half of the distance between the nucleus of two identical atoms when these are in close contact with each other is called Atomic Radius.
Unit
It is measured in angstrom unit A.
It is measured in angstrom unit A.
Trend in Period
The atomic radii decreases from left to right within a period in the periodic table. This is because nuclear charge increases with the increase of atomic number. But the number of shells remains same within a period.
The atomic radii decreases from left to right within a period in the periodic table. This is because nuclear charge increases with the increase of atomic number. But the number of shells remains same within a period.
Trend in Group
Atomic radius increases from top to bottom in a group. This is because, although nuclear charge increases from top to bottom but at the same time on new shell is also added for each successive element down the group.
Atomic radius increases from top to bottom in a group. This is because, although nuclear charge increases from top to bottom but at the same time on new shell is also added for each successive element down the group.
Ionization Energy (I.E) or Ionization Potential (I.P)
Definition
The minimum energy needed to remove an electron from an isolated, gaseous atom in its ground state is called Ionization Energy.
The minimum energy needed to remove an electron from an isolated, gaseous atom in its ground state is called Ionization Energy.
Unit
It is expressed in electron volts or kilo-joules permole.
1 ev = 96.49kj
It is expressed in electron volts or kilo-joules permole.
1 ev = 96.49kj
Factors Affecting Ionization Energy
The ionization energy of elements depends upon the following factors:
1. Effect of Nuclear Charge on I.E
The greater the nuclear charge the higher is the ionization energy.
2. Effect of Atomic Size
The larger the size of atom the lower is the ionization energy.
The ionization energy of elements depends upon the following factors:
1. Effect of Nuclear Charge on I.E
The greater the nuclear charge the higher is the ionization energy.
2. Effect of Atomic Size
The larger the size of atom the lower is the ionization energy.
Trend of I.E in Period
Ionization energy increases from left to right in a period due to increase in nuclear change and decrease in atomic size.
Ionization energy increases from left to right in a period due to increase in nuclear change and decrease in atomic size.
Trend of I.E in Group
I.E decreases from top to bottom in a group due to increase in atomic size.
I.E decreases from top to bottom in a group due to increase in atomic size.
Electronegativity
Definition
The tendency of each atom in a covalent molecule to attract a shared pair of electrons towards itself is known as its electronegativity.
The tendency of each atom in a covalent molecule to attract a shared pair of electrons towards itself is known as its electronegativity.
Factors Affecting Electronegativity
Electronegativity depends upon the following factors:
Atomic size
Atomic Number
Electron Affinity
Ionization Energy
Electronegativity depends upon the following factors:
Atomic size
Atomic Number
Electron Affinity
Ionization Energy
Trend or Variation in the Period
Electronegativity increases from left to right within a period due to increase in nuclear charge and decrease in atomic size.
Electronegativity increases from left to right within a period due to increase in nuclear charge and decrease in atomic size.
Trend or Variation in the Group
Electronegativity values decreases from top to bottom within a group due to increase in atomic size.
Electronegativity values decreases from top to bottom within a group due to increase in atomic size.
Electron Affinity
Definition
The energy change that occurs when an electron is gained by an atom in the gaseous state is known as Electron Affinity.
Electron Affinity for the addition of first electron is negative i.e. energy is released but for further addition of electrons it is positive because energy has to be added to over come repulsion between negative ion and electron.
The energy change that occurs when an electron is gained by an atom in the gaseous state is known as Electron Affinity.
Electron Affinity for the addition of first electron is negative i.e. energy is released but for further addition of electrons it is positive because energy has to be added to over come repulsion between negative ion and electron.
Unit
It is measured in KJ/mol or in e.v per atom.
It is measured in KJ/mol or in e.v per atom.
Factors Affecting Electron Affinity
Atomic Size
Nuclear Charge
Atomic Size
Nuclear Charge
Trend or Variation of Electron Affinity in Group
Down the group in the periodic table, electron affinity decreases because the addition of a new shell to each atom decreases its force of attraction.
Down the group in the periodic table, electron affinity decreases because the addition of a new shell to each atom decreases its force of attraction.
Trend or Variation of Electron Affinity in Period
In a period, the electron affinity increases from left to right because the incoming successive atoms have higher nuclear charge and attract electron more towards itself.
In a period, the electron affinity increases from left to right because the incoming successive atoms have higher nuclear charge and attract electron more towards itself.
Chapter 06 | States of Matter | Ninth Class Chemistry Notes
States of Matter
Matter has three states:
1. Gas
2. Liquid
3. solid
These are physical states of matter. The three states of one matter may have different physical properties while their chemical properties are same. Water exists in three physical states solid (ice), liquid and gas(steam) has same chemical properties.
1. Gas
2. Liquid
3. solid
These are physical states of matter. The three states of one matter may have different physical properties while their chemical properties are same. Water exists in three physical states solid (ice), liquid and gas(steam) has same chemical properties.
Kinetic Theory of Matter
The Kinetic theory was presented to explain the properties of gases and is called kinetic theory of gases. But this theory was also able to explain the composition of liquid and solid state of matter. So its is called Kinetic Theory of Matter.
According to Kinetic Theory of matter:
1. All matter is composed of atoms, molecules or ions.
2. These particles have kinetic energy due to which they are in the state of motion.
3. In gaseous state, these particles move in a straight line. They collide with one another and with the walls of container. In liquids the rate of their movement is very small but in solids, there is to and fro motion only.
4. Generally material particles can have three types of movements, i.e. translational, rotational and vibrational.
According to Kinetic Theory of matter:
1. All matter is composed of atoms, molecules or ions.
2. These particles have kinetic energy due to which they are in the state of motion.
3. In gaseous state, these particles move in a straight line. They collide with one another and with the walls of container. In liquids the rate of their movement is very small but in solids, there is to and fro motion only.
4. Generally material particles can have three types of movements, i.e. translational, rotational and vibrational.
Solids
The state of matter which has definite shape and volume is called solid.
Properties of Solids
1. Definite Volume and Shape
The cohesive forces in solid substances are so strong that they keep their particles arranged in fixed positions. So due to restrict movements of particles, the solids have definite volume and shape.
The cohesive forces in solid substances are so strong that they keep their particles arranged in fixed positions. So due to restrict movements of particles, the solids have definite volume and shape.
2.Motion of Particles
The solid particles have vibrational motion only because these particles are held in fixed position by strong cohesive forces.
The solid particles have vibrational motion only because these particles are held in fixed position by strong cohesive forces.
3. Effect of Heat
The physical state of solid substance can be changed by heating. On heating solid is converted to liquid and gaseous state. Heat increases the kinetic energy of the particles and they start vibrating at higher frequency. At a particular temperature the vibrational motions become fast that they overcome the cohesive forces and solid melts to liquid.
The physical state of solid substance can be changed by heating. On heating solid is converted to liquid and gaseous state. Heat increases the kinetic energy of the particles and they start vibrating at higher frequency. At a particular temperature the vibrational motions become fast that they overcome the cohesive forces and solid melts to liquid.
4. Melting Point
The temperature at which the solid is converted to liquid on heating is called melting point. At melting point, the particles of solid loose their means position and their arrangement. The solid collapses and turns to liquid.
The temperature at which the solid is converted to liquid on heating is called melting point. At melting point, the particles of solid loose their means position and their arrangement. The solid collapses and turns to liquid.
5. Sublimation
The conversion of some solids directly into gaseous state on heating is called sublimation. Iodine, ammonium chloride and naphthalene change directly into vapour state upon heating.
The conversion of some solids directly into gaseous state on heating is called sublimation. Iodine, ammonium chloride and naphthalene change directly into vapour state upon heating.
Liquid
The state of matter having definite volume but indefinite shape is called liquid.
Properties of Liquid
1. Volume
Liquids have definite volume. In liquid particles are very close to one another and have cohesive forces among the particles. Due to the presence of cohesive forces, liquids have definite volume and keep their level as well.
Liquids have definite volume. In liquid particles are very close to one another and have cohesive forces among the particles. Due to the presence of cohesive forces, liquids have definite volume and keep their level as well.
2. Shape
Liquids do not have any specific shape. They adopt the shape of the container. The molecules of liquid are able to move. Due to this random motion the molecules of liquid do not have fixed position and as a result, a liquid does not have any specific shape.
Liquids do not have any specific shape. They adopt the shape of the container. The molecules of liquid are able to move. Due to this random motion the molecules of liquid do not have fixed position and as a result, a liquid does not have any specific shape.
3. Evaporation
Conversion of liquid into its vapours at any temperature is called evaporation. The molecules of liquid come to the surface of liquid and escape by overcoming cohesive forces. So liquid is converted to vapours at all temperature.
Conversion of liquid into its vapours at any temperature is called evaporation. The molecules of liquid come to the surface of liquid and escape by overcoming cohesive forces. So liquid is converted to vapours at all temperature.
4. Boiling Point
The temperature of a liquid at which its vapour pressure becomes equal to the atmospheric pressure is called boiling point.
The temperature of a liquid at which its vapour pressure becomes equal to the atmospheric pressure is called boiling point.
Gas
The state of matter which does not have definite shape and volume is called gaseous state.
Properties of Gaseous State
1. Indefinite Volume and Shape
In gaseous state, the molecules have insignificant cohesive forces among themselves. They move very fast in all possible directions. As a result, a gas neither has fixed shape nor a fixed volume.
In gaseous state, the molecules have insignificant cohesive forces among themselves. They move very fast in all possible directions. As a result, a gas neither has fixed shape nor a fixed volume.
2. Kinetic Energy of the Particle of a Gas
Gas particles have very high kinetic energy as compared to liquid and solid state.
Gas particles have very high kinetic energy as compared to liquid and solid state.
3. Pressure
The molecules of a gas are in the state of random motion. The molecules of gas not only collide with one another but also with the walls of the container in which they are enclosed. Due to their collision, the velocity of the molecules changes every moment. The pressure exerted by gas is also due to the collision of its molecules with the walls of the container.
The molecules of a gas are in the state of random motion. The molecules of gas not only collide with one another but also with the walls of the container in which they are enclosed. Due to their collision, the velocity of the molecules changes every moment. The pressure exerted by gas is also due to the collision of its molecules with the walls of the container.
4. Elastic Collision
The collision of gas molecules is elastic in nature which means that the total energy of the colliding molecules remains the same before and after the collision.
The collision of gas molecules is elastic in nature which means that the total energy of the colliding molecules remains the same before and after the collision.
5. Kinetic Energy
The kinetic energy of molecules of gas is very high as compared with solid and liquid.
The kinetic energy of molecules of gas is very high as compared with solid and liquid.
Diffusion
The movement of molecules from a higher concentration to a lower concentration is known as Diffusion.
If the concentration of molecules at a particular place is higher, they start moving towards a place where their concentration is lower. When the concentration of molecules at both the places becomes equal the process of diffusion stops.
If the concentration of molecules at a particular place is higher, they start moving towards a place where their concentration is lower. When the concentration of molecules at both the places becomes equal the process of diffusion stops.
Diffusion in Gases
The molecules of one gas can diffuse easily into the molecules of other gas. For example if an open bottle of a perfume is kept in a room, its smell will spread uniformly throughout the room. The liquid perfume present in the bottle volatilized slowly and its vapours diffuse through out the room.
Graham’s Law of Diffusion
Scottish Chemist, Thomas Graham (1833) discovered that lighter gs can diffuse through porous pot faster than the heavier one. This is called Graham’s
Law of Diffusion.
Hydrogen being lighter gas will diffuse faster than oxygen or carbon dioxide.
Hydrogen being lighter gas will diffuse faster than oxygen or carbon dioxide.
Diffusion in Liquids
Liquid molecules can also diffuse because they have free movement. Since the molecules of liquid move comparatively slowly than gas molecule, their rate of diffusion are also lesser than gases.
Brownian Movement
Robert Brown (1927) discovered this phenomenon:
The free movement of the molecules of gases and liquid is called Brownian Movement.”
The free movement of the molecules of gases and liquid is called Brownian Movement.”
When a pollen grain is put in water. The movement of pollen grain in water is observed by microscope. It is observed that pollen grain is continuously moving in all directions. This free movement of pollen grain was due to the free movement of water molecules. The colliding water molecules will also force pollen grain to move as well. The students can observe Brownian movement with the help of simple experiment.
Experiment
Put a drop of milk on a microscope slide and cover it with cover slip. Put it under microscope and observe it. You will see small particle of fat moving randomly in milk. The movement of fat particles is actually due to the movement of water molecules in milk.
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Chapter 07 | Solution and Suspension | Ninth Class Chemistry Notes
Solution
The size of particles is between 0.1 to 1nm.
2. Particles cannot be seen with low power microscope.
3. It is homogeneous.
4. Particles do not settle down.
5. It is transparent.
6. Components cannot be separated by filtration.
2. Particles cannot be seen with low power microscope.
3. It is homogeneous.
4. Particles do not settle down.
5. It is transparent.
6. Components cannot be separated by filtration.
Suspension
1. The size of particles is larger than 1000nm.
2. Particles can be seen by low power microscope.
3. It is heterogeneous.
4. Particles settle down.
5. It is not transparent.
6. Components can be separated by filtration.
1. The size of particles is larger than 1000nm.
2. Particles can be seen by low power microscope.
3. It is heterogeneous.
4. Particles settle down.
5. It is not transparent.
6. Components can be separated by filtration.
Solution and Suspension
Solution
A homogeneous mixture of different chemical substances which has uniform chemical composition through out and shows uniform physical properties is called solution. For example dissolve a small amount of copper sulphate in water the water will become blue. If this blue liquid is filtered, it will pass through the filter paper without leaving any solid. The mixture thus prepared is called a solution.
Binary Solution
A solution which is formed by mixing two substances is called binary solution. For example solution of glucose and water.
Solute
The component of a binary solution which is in lesser amount is called solute. For example in copper sulphate solution, copper sulphate is solute.
Solvent
The component of a binary solution which is in greater amount is called solvent. For example in copper sulphate solution, water is solvent.
Saturated solution
A solution in which maximum amount of a solute has been dissolved at a particular temperature and in which the dissolved form of solute is at equilibrium with its undissolved form is called saturated solution.
Unsaturated Solution
Solution which can dissolve further amount of a solute at a [particular temperature is called an unsaturated solution.
Supersaturated Solution
The solution which contains even more amount of solute required to prepare saturated solution is called super saturated solution. The hot saturated solution of compound like sodium thiosulphate does not crystallize its solute if cooled slowly without disturbance. Such a solution is called supersaturated solution.
Dilute Solution
A solution which contains small amount of a solute as compared to the solvent is called dilute solution.
Concentrated Solution
A solution which contains excess amount of a solute as compared to that of a solvent is called a concentrated solution.
Concentrated Solution
The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount o solute and solvent present in it.
Concentration of Solution
The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount of solute and solvent present in it.
Percentage by Mass
The percentage of solute by mass is the mass of solute present in hundred part of the solution. For example 5% hydrogen peroxide solution by mass means that 5g hydrogen peroxide are dissolved in 95g of water to give 100g of solution.
Percentage of Mass = (Mass of Solute/Mass of Solution) x 100
The percentage of solute by mass is the mass of solute present in hundred part of the solution. For example 5% hydrogen peroxide solution by mass means that 5g hydrogen peroxide are dissolved in 95g of water to give 100g of solution.
Percentage of Mass = (Mass of Solute/Mass of Solution) x 100
Percentage by Volume
The concentration unit expresses the volume of solute present in 100cm3 of solution. For example 15% solution of alcohol by volume will mean that 15cm3 alcohols are present in 100cm3 of solution. (Here 3 represents cube)
Percentage by Volume = (Volume of Solute/Volume of Solution) x 100
The concentration unit expresses the volume of solute present in 100cm3 of solution. For example 15% solution of alcohol by volume will mean that 15cm3 alcohols are present in 100cm3 of solution. (Here 3 represents cube)
Percentage by Volume = (Volume of Solute/Volume of Solution) x 100
Molar Solution
The solution that contains one mole of solute in 1dm3 of solution is called a molar solution. The concentration of this solution is expressed as M.
The solution that contains one mole of solute in 1dm3 of solution is called a molar solution. The concentration of this solution is expressed as M.
Molarity
Molarity of a solution is the number of moles of solute present in 1dm3 of the solution. It is expressed as M.
M = Number of Moles of Solute/Volume of Solution in dm3
or
M = (Mass of solute/Molecular Mass) x (1/ Volume of Solution in dm3)
Molarity of a solution is the number of moles of solute present in 1dm3 of the solution. It is expressed as M.
M = Number of Moles of Solute/Volume of Solution in dm3
or
M = (Mass of solute/Molecular Mass) x (1/ Volume of Solution in dm3)
Crystallization
The process in which crystal separates from saturated solution on cooling is called crystallization. It is a useful process because it can be used to purify the impure solid compounds. It can also be used to separate a mixture of solids.
Hydration
The ions surrounded by solvent molecules in solution are called solvated ions. If water is a solvent these ions are called hydrated ions.
Suspension
A suspension in such a mixture in which solute particles do not dissolved in solvent and if filtrated its particles do not pass through the pores of filter paper.
Colloidal Solution
In a colloidal solution the solute particles are slightly bigger than those present in a true solution but not big enough to seen with naked eye.
Standard Solution
A solution whose molarity (strength) is known is called Standard Solution.
True Solution
A True Solution is such a mixture in which solute particles are completely homogenized in the solvent for example solution of sodium chloride or copper sulphate in water.
Solubility
Solubility o a solute in a particular solvent is defined as the amount of solute in grams, which can dissolve in 100g of the solvent at a particular temperature to give a saturated solution.
or
The amount of a solute in gram moles, which can dissolve in one kilogram of the solvent at a particular temperature, to give a saturated solution.
or
The amount of a solute in gram moles, which can dissolve in one kilogram of the solvent at a particular temperature, to give a saturated solution.
Factors Affecting the Solubility
Effect of Solvent
Similar solvents dissolve similar solutes, i.e. if the chemical structure and the electrical properties such as dipole moment of solute and solvent are similar, the solubility will increase. If there is dissimilarity in properties, then either the solute will not dissolve or there will be very little solubility.
Similar solvents dissolve similar solutes, i.e. if the chemical structure and the electrical properties such as dipole moment of solute and solvent are similar, the solubility will increase. If there is dissimilarity in properties, then either the solute will not dissolve or there will be very little solubility.
Effect of Solute
Different solutes have different solubility’s in a particular solvent e.g. if the saturated solutions of table sugar and sodium chloride are prepared, it is found that the concentration of sodium chloride solution is 5.3 molar while that of sugar solution is 3.8 molar. In other words, the solubility of sodium chloride in water is far greater than that of sugar. This is due to the fact that the attraction of sodium (Na+ and chloride (Cl-) ions with water is greater than that of sugar molecules with water.
Different solutes have different solubility’s in a particular solvent e.g. if the saturated solutions of table sugar and sodium chloride are prepared, it is found that the concentration of sodium chloride solution is 5.3 molar while that of sugar solution is 3.8 molar. In other words, the solubility of sodium chloride in water is far greater than that of sugar. This is due to the fact that the attraction of sodium (Na+ and chloride (Cl-) ions with water is greater than that of sugar molecules with water.
Effect of Temperature
Change in temperature has different effects on the solubility of different compounds. Usually the solubility increase with the increase in temperature but it cannot be taken as a general rule. The solubility of compounds like lithium carbonate, calcium chromate decreases with the increase in temperature. The solubility of gases in water also decreases with the increase in temperature. On the other hand, there are a large number of compounds whose solubility in water increase with the increase in temperature e.g. sodium nitrate, silver nitrate, Potassium chloride etc. the solubility of sodium chloride in water does not increase appreciably with the increase in temperature.
Change in temperature has different effects on the solubility of different compounds. Usually the solubility increase with the increase in temperature but it cannot be taken as a general rule. The solubility of compounds like lithium carbonate, calcium chromate decreases with the increase in temperature. The solubility of gases in water also decreases with the increase in temperature. On the other hand, there are a large number of compounds whose solubility in water increase with the increase in temperature e.g. sodium nitrate, silver nitrate, Potassium chloride etc. the solubility of sodium chloride in water does not increase appreciably with the increase in temperature.
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Chapter 08 | Electro Chemistry | Ninth Class Chemistry Notes
Electro-Chemistry
The branch of chemistry which deals with the study of chemical energy to electrical energy or electrical energy to chemical energy is called electro-chemistry.
Conductors
Those substances through which electric current can pass are called conductors. For example all metals are conductors.
Non-Conductors
Those substances through which electric current cannot pass are called non-conductors. For example plastic, wood are non-conductors.
Electrolysis
The process in which electricity passes through the aqueous or infused state of some substance. The substances itself decompose into its component. This process is called electrolysis.
Electrolyte
The compound in molten state or in aqueous solution through which electricity can pass are called electrolyte.
Non-Electrolyte
Those compounds through which electricity cannot pass are called non-electrolyte.
Strong Electrolyte
The substances which are highly soluble and completely ionized are called strong electrolyte. For example acids, bases and salts are strong electrolytes.
Weak Electrolyte
The substances which are not highly soluble and remain in un-ionized form are called weak electrolyte.
Electroplating
A process in which metal is deposited on the surface of another metal by electrolysis is called electroplating.
Objectives of Electroplating
Decoration
It is done for decoration. Noble and precious metals like gold or silver are deposited on the inferior metals to enhance their beauty and look beautiful.
It is done for decoration. Noble and precious metals like gold or silver are deposited on the inferior metals to enhance their beauty and look beautiful.
Protection
Electroplating is done to protect the metals from rusting as well as from attack of other substance like organic acids and acidic gases.
Electroplating is done to protect the metals from rusting as well as from attack of other substance like organic acids and acidic gases.
Repair
It can be used to repair the broken machinery by electroplating with other metals. Usually the metals like copper, silver, chromium, nickel and gold are used for electroplating.
It can be used to repair the broken machinery by electroplating with other metals. Usually the metals like copper, silver, chromium, nickel and gold are used for electroplating.
Procedure of Electroplating
The metal which is to be electroplated is first cleaned with sand and then washed with caustic soda solution and finally with a lot of water.
This metal is made cathode and the metal which is going to be deposited is made anode. The electrolyte is a salt of metal being deposited and electroplating is carried out in a tank made of cement, glass or wood. It is called an electrolytic tank.
The electrolyte should have following properties:
1. It must be very soluble in water.
2. It must be good conductor.
3. Cheap
4. May not easily oxidized or reduced or hydrolyzed.
(Diagram)
The metal which is to be electroplated is first cleaned with sand and then washed with caustic soda solution and finally with a lot of water.
This metal is made cathode and the metal which is going to be deposited is made anode. The electrolyte is a salt of metal being deposited and electroplating is carried out in a tank made of cement, glass or wood. It is called an electrolytic tank.
The electrolyte should have following properties:
1. It must be very soluble in water.
2. It must be good conductor.
3. Cheap
4. May not easily oxidized or reduced or hydrolyzed.
(Diagram)
Differences | Ninth Class Chemistry Notes
Metals and Non Metals
Metals
1. Metals have luster shine surface.
2. Metals reflect heat and light.
3. Metals conduct heat and electricity
4. Metals are ductile and can be drawn into wire.
1. Metals have luster shine surface.
2. Metals reflect heat and light.
3. Metals conduct heat and electricity
4. Metals are ductile and can be drawn into wire.
Non-Metals
1. Non-Metals have no luster.
2. Non-Metals usually don’t reflect heat and light.
3. Non-Metals do not conduct heat and electricity.
4. Non-Metals are non ductile and cannot be drawn into wire.
5. Non-Metals are non-malleable and can not form sheets.
1. Non-Metals have no luster.
2. Non-Metals usually don’t reflect heat and light.
3. Non-Metals do not conduct heat and electricity.
4. Non-Metals are non ductile and cannot be drawn into wire.
5. Non-Metals are non-malleable and can not form sheets.
Homogeneous and Heterogeneous Mixture
Homogeneous Mixture
1. Those mixtures, which have uniform composition throughout their mass are called homogeneous mixtures.
2. Homogeneous mixture has only one phase through out its mass.
3. Homogeneous mixture are also known as solution.
4. Examples: Salt and water, Sugar and water.
1. Those mixtures, which have uniform composition throughout their mass are called homogeneous mixtures.
2. Homogeneous mixture has only one phase through out its mass.
3. Homogeneous mixture are also known as solution.
4. Examples: Salt and water, Sugar and water.
Heterogeneous Mixture
1. Those mixtures, which do not have uniform composition through their mass are called Heterogeneous Mixture.
2. Heterogeneous Mixture has more than one phase through out its mass.
3. Heterogeneous Mixture are not solutions.
4. Examples: Rocks, Soil, Food products.
1. Those mixtures, which do not have uniform composition through their mass are called Heterogeneous Mixture.
2. Heterogeneous Mixture has more than one phase through out its mass.
3. Heterogeneous Mixture are not solutions.
4. Examples: Rocks, Soil, Food products.
Molecular and Empirical Formula
Molecular Formula
1. Formula which shows the actual number of atoms of each element present in a molecule is called Molecular Formula.
2. Molecular Formula shows the structure of compound.
3. Two or more compounds cannot have same Molecular Formula.
4. Molecular Formula = n x Empirical Formula.
5. It represents covalent compounds only.
1. Formula which shows the actual number of atoms of each element present in a molecule is called Molecular Formula.
2. Molecular Formula shows the structure of compound.
3. Two or more compounds cannot have same Molecular Formula.
4. Molecular Formula = n x Empirical Formula.
5. It represents covalent compounds only.
Empirical Formula
1. formula, which shows the relative ratio of atoms of each element present in a molecule, is called Empirical Formula.
2. Empirical Formula can not show the structure of compound.
3. Two or more compounds can have same Empirical Formula.
4. Empirical Formula = Molecular Formula / n
5. It represent an ionic compound as well as a covalent compound.
1. formula, which shows the relative ratio of atoms of each element present in a molecule, is called Empirical Formula.
2. Empirical Formula can not show the structure of compound.
3. Two or more compounds can have same Empirical Formula.
4. Empirical Formula = Molecular Formula / n
5. It represent an ionic compound as well as a covalent compound.
Symbol and Formula
Symbol
1. A symbol is an abbreviation for the chemical name of an element and represents only one atom of the element.
2. It represents one atom of an element.
3. Symbol is written for elements.
4. Examples: Na, Br, Cl, F etc.
1. A symbol is an abbreviation for the chemical name of an element and represents only one atom of the element.
2. It represents one atom of an element.
3. Symbol is written for elements.
4. Examples: Na, Br, Cl, F etc.
Formula
1. Representation of compound in terms of symbols is called formula. It represents one atom of an element.
2. It represents atoms of same or different elements present in one molecule.
3. It represents an ionic compounds as well as a covalent compound.
4. Examples: H2O, NH3 etc.
1. Representation of compound in terms of symbols is called formula. It represents one atom of an element.
2. It represents atoms of same or different elements present in one molecule.
3. It represents an ionic compounds as well as a covalent compound.
4. Examples: H2O, NH3 etc.
Gram and Gram Molecule
Gram
The atomic mass of an element expressed in grams is called gram atomic mass.
2. It is associated with element only.
3. It is the mass of one atomic mole.
4. One gram atom of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).
The atomic mass of an element expressed in grams is called gram atomic mass.
2. It is associated with element only.
3. It is the mass of one atomic mole.
4. One gram atom of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).
Gram Molecule
1. Molecular mass of any element or compound expressed in grams is called gram molecule.
2. It is associated with element and compound.
3. It is the mass of one molecular mole.
4. One gram molecule of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).
1. Molecular mass of any element or compound expressed in grams is called gram molecule.
2. It is associated with element and compound.
3. It is the mass of one molecular mole.
4. One gram molecule of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).
Atom and Molecule
Atom
1. It is the smallest particle of an element which can enter into a chemical reaction.
2. It is represented by a symbol of the element.
3. It shows the properties of the element.
4. It retains its identity in a chemical reaction.
1. It is the smallest particle of an element which can enter into a chemical reaction.
2. It is represented by a symbol of the element.
3. It shows the properties of the element.
4. It retains its identity in a chemical reaction.
Molecule
1. It is the smallest particle of a substance which can exist and show all the properties of the substance.
2. It is represented by a molecular formula of the substance.
3. It shows the properties of the substance.
4. It does not retain its identity in a chemical reaction.
1. It is the smallest particle of a substance which can exist and show all the properties of the substance.
2. It is represented by a molecular formula of the substance.
3. It shows the properties of the substance.
4. It does not retain its identity in a chemical reaction.
Exothermic and Endothermic Reactions
Exothermic Reaction
1. Those chemical reactions in which heat energy is evolved are called exothermic reactions.
2. In exothermic reactions the enthalpy of products is lower than the reactants. H is therefore negative for an exothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.
1. Those chemical reactions in which heat energy is evolved are called exothermic reactions.
2. In exothermic reactions the enthalpy of products is lower than the reactants. H is therefore negative for an exothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.
Endothermic Reactions
1. Those chemical reactions in which heat energy is absorbed are called endothermic reactions.
2. In endothermic reactions the enthalpy of reactants is lower than the products. H is therefore positive in endothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.
1. Those chemical reactions in which heat energy is absorbed are called endothermic reactions.
2. In endothermic reactions the enthalpy of reactants is lower than the products. H is therefore positive in endothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.
Physical and Chemical Properties
Physical Properties
1. The physical properties of a substance are those characteristics which serve to distinguish it from other substance but do not deal with its ability to undergo chemical changes.
2. These are related to the physical state of matter.
3. Examples: Formation of ice from water, formation of a magnet from ice etc.
1. The physical properties of a substance are those characteristics which serve to distinguish it from other substance but do not deal with its ability to undergo chemical changes.
2. These are related to the physical state of matter.
3. Examples: Formation of ice from water, formation of a magnet from ice etc.
Chemical Properties
1. The chemical properties of a substance indicate the ability of a substance to undergo chemical changes.
2. They are related to the chemical change of a substance.
3. Examples: burning of paper, rusting of iron.
1. The chemical properties of a substance indicate the ability of a substance to undergo chemical changes.
2. They are related to the chemical change of a substance.
3. Examples: burning of paper, rusting of iron.
Electrolyte and Non-Electrolyte
Electrolytes
1. Electrolytes conduct electricity in molten or in solution form.
2. These form positive and negative ions when dissolved in water e.g. NaCl form Na+ and Cl- ions when dissolved in water.
3. Chemical changes occur when electric current is passed through the electrolyte.
4. Generally these are ionic or polar covalent compounds.
1. Electrolytes conduct electricity in molten or in solution form.
2. These form positive and negative ions when dissolved in water e.g. NaCl form Na+ and Cl- ions when dissolved in water.
3. Chemical changes occur when electric current is passed through the electrolyte.
4. Generally these are ionic or polar covalent compounds.
Non-Electrolytes
1. Non-electrolytes do not conduct electric current in molten or in solution form.
2. These do not form positive and negative ions when dissolved in water e.g. Urea, sugar, glucose etc.
2. No chemical change occurs in them on passing current.
3. Generally these are non polar covalent compounds.
4. Generally these are non polar covalent compounds.
1. Non-electrolytes do not conduct electric current in molten or in solution form.
2. These do not form positive and negative ions when dissolved in water e.g. Urea, sugar, glucose etc.
2. No chemical change occurs in them on passing current.
3. Generally these are non polar covalent compounds.
4. Generally these are non polar covalent compounds.
Acid and Base
Acid
1. Those compounds which provide hydrogen ion (H+) in aqueous solutions are called Acids.
2. An acid is a substance which produces H+ ions in aqueous solution.
3. Acid is a species (a compound or ion) which donates or tends to donate a proton (H+).
4. An acid is a species (molecule or ion) which can accept a pair of electron. An acid is also called an electrophile (electron loving).
5. They have sour taste.
6. Acid turn blue litmus red methyl orange red.
1. Those compounds which provide hydrogen ion (H+) in aqueous solutions are called Acids.
2. An acid is a substance which produces H+ ions in aqueous solution.
3. Acid is a species (a compound or ion) which donates or tends to donate a proton (H+).
4. An acid is a species (molecule or ion) which can accept a pair of electron. An acid is also called an electrophile (electron loving).
5. They have sour taste.
6. Acid turn blue litmus red methyl orange red.
Base
1. Those compounds, which provides hydroxyl (OH-) ion in aqueous solution, are called bases.
2. A base is a substance, which gives (OH-) in aqueous solution.
3. A base is a species, which accepts or tends to accept a proton.
4. A base is a species (molecule or ion) which can donate a pair of electrons. A base is also called a nucleophile (Nucleus loving).
5. Bases have bitter taste.
6. Bases turn red litmus to blue, colorless phenolphthalein to pink and methyl orange to yellow.
1. Those compounds, which provides hydroxyl (OH-) ion in aqueous solution, are called bases.
2. A base is a substance, which gives (OH-) in aqueous solution.
3. A base is a species, which accepts or tends to accept a proton.
4. A base is a species (molecule or ion) which can donate a pair of electrons. A base is also called a nucleophile (Nucleus loving).
5. Bases have bitter taste.
6. Bases turn red litmus to blue, colorless phenolphthalein to pink and methyl orange to yellow.
Ionic and Covalent Bond
Ionic Bond
1. Ionic bond is formed by complete transfer of electrons from one atom to another atom.
2. Ionic bond is always formed between different atoms. E.g. NaCl, CaCl2.
3. In ionic bond atoms have very large electro-negativity and ionization energy difference.
4. This bond is usually formed between metals and non-metals.
5. This bond is very strong.
6. As a result of this bond ionic compounds are formed.
7. It is always formed between two different atoms.
8. It is formed when difference of electro-negativity of combining atoms is 1.7 or more.
1. Ionic bond is formed by complete transfer of electrons from one atom to another atom.
2. Ionic bond is always formed between different atoms. E.g. NaCl, CaCl2.
3. In ionic bond atoms have very large electro-negativity and ionization energy difference.
4. This bond is usually formed between metals and non-metals.
5. This bond is very strong.
6. As a result of this bond ionic compounds are formed.
7. It is always formed between two different atoms.
8. It is formed when difference of electro-negativity of combining atoms is 1.7 or more.
Covalent Bond
1. Covalent bond is formed by the mutual sharing of electrons between two atoms.
2. Covalent bond may be formed between similar or dissimilar atoms e.g. H2, O2, HCl etc.
3. In covalent bond atoms have very small electro-negativity or ionization energy difference.
4. This bond is usually formed between non-metals only.
5. This bond is comparatively less strong.
6. As a result of this bond covalent compounds are formed.
7. It is formed between similar and different types of atoms.
8. It is formed when difference of electro-negativity of combining atoms is less than 1.7.
1. Covalent bond is formed by the mutual sharing of electrons between two atoms.
2. Covalent bond may be formed between similar or dissimilar atoms e.g. H2, O2, HCl etc.
3. In covalent bond atoms have very small electro-negativity or ionization energy difference.
4. This bond is usually formed between non-metals only.
5. This bond is comparatively less strong.
6. As a result of this bond covalent compounds are formed.
7. It is formed between similar and different types of atoms.
8. It is formed when difference of electro-negativity of combining atoms is less than 1.7.
Ionic and Covalent Compounds
Ionic Compounds
1. The ionic compounds are usually solid, hard and brittle.
2. The ionic compounds are good conductors of electricity either in fused state or in the form of aqueous solution.
3. Ionic Compounds have high melting points and boiling points.
4. Ionic compounds have high melting points and boiling points.
5. Covalent compounds are mostly volatile.
1. The ionic compounds are usually solid, hard and brittle.
2. The ionic compounds are good conductors of electricity either in fused state or in the form of aqueous solution.
3. Ionic Compounds have high melting points and boiling points.
4. Ionic compounds have high melting points and boiling points.
5. Covalent compounds are mostly volatile.
Covalent Compounds
1. Covalent compounds exist in all the three states i.e. gas, liquid and solid.
2. A pure covalent compound does not conduct electricity.
3. These have usually low melting and boiling points.
4. These are soluble in water.
5. These are insoluble in water but soluble in organic solvents.
1. Covalent compounds exist in all the three states i.e. gas, liquid and solid.
2. A pure covalent compound does not conduct electricity.
3. These have usually low melting and boiling points.
4. These are soluble in water.
5. These are insoluble in water but soluble in organic solvents.
Co-Ordinate Covalent and Covalent Bond
Co-Ordinate Covalent Bond
1. It is a bond in which the shared electron pair is denoted by one atom only.
2. One atom donates electrons but other has no contribution.
3. Lewis acids and bases always from this bond.
4. It is represented by ->.
5. It is formed by the donation of an electron apir by one of the two bonded atoms.
6. It is formed by the completely filled atomic orbital.
1. It is a bond in which the shared electron pair is denoted by one atom only.
2. One atom donates electrons but other has no contribution.
3. Lewis acids and bases always from this bond.
4. It is represented by ->.
5. It is formed by the donation of an electron apir by one of the two bonded atoms.
6. It is formed by the completely filled atomic orbital.
Covalent Bond
1. It is a bond formed by the mutual sharing of electrons.
2. In the shared electron pair both atoms have equal contribution.
3. Lewis acids and bases do not form this bond.
4. It is represented by _.
5. It is formed by the mutual sharing of electrons between atoms.
6. It is formed by the overlap of partially filled atomic orbital.
1. It is a bond formed by the mutual sharing of electrons.
2. In the shared electron pair both atoms have equal contribution.
3. Lewis acids and bases do not form this bond.
4. It is represented by _.
5. It is formed by the mutual sharing of electrons between atoms.
6. It is formed by the overlap of partially filled atomic orbital.
Polar and Non-Polar Covalent Bond
Polar Covalent Bond
1. The covalent bond between two atoms having different electro-negativity is called a polar covalent bond.
2. In a polar bond, the shared electron pair is not equally attracted by the bonded atoms.
3. Bonded atoms become slightly charged and acquire partial =ve and -ve charges.
4. It has an ionic character.
5. The bond energy is greater.
1. The covalent bond between two atoms having different electro-negativity is called a polar covalent bond.
2. In a polar bond, the shared electron pair is not equally attracted by the bonded atoms.
3. Bonded atoms become slightly charged and acquire partial =ve and -ve charges.
4. It has an ionic character.
5. The bond energy is greater.
Non-Polar Covalent Bond
1. The covalent bond between two atoms having same electro-negativity is called a non-polar covalent bond.
2. In a non polar bond, the shared electron pair is equally attracted by the bonded atoms.
3. Bonded atoms remain electrically neutral and do not acquire partial charges.
4. It has no ionic character.
5. The bond energy is lesser.
1. The covalent bond between two atoms having same electro-negativity is called a non-polar covalent bond.
2. In a non polar bond, the shared electron pair is equally attracted by the bonded atoms.
3. Bonded atoms remain electrically neutral and do not acquire partial charges.
4. It has no ionic character.
5. The bond energy is lesser.
Electrolytic and Galvanic or Voltaic Cell
Electrolytic Cell
1. It is a device for converting electrical energy into chemical energy. It means by passing current through an electrolyte, chemical reaction takes place.
2. It consists of a vessel containing an electrodes and a source of direct current (battery).
3. Example: Electrolysis of aqueous solution of NaCl.
1. It is a device for converting electrical energy into chemical energy. It means by passing current through an electrolyte, chemical reaction takes place.
2. It consists of a vessel containing an electrodes and a source of direct current (battery).
3. Example: Electrolysis of aqueous solution of NaCl.
Galvanic or Voltaic Cell
1. It is a device for converting chemical energy into electrical energy. It means spontaneous redox reaction is used for the production of electric current. This cell was prepared by L.Galvani and A.Volts, hence named as Galvanic or Voltaic Cell.
2. It consists of two half-cells. Each half cell consists of an electrodes and the solution with which it is in contact.
3. Example: Daniel Cell-Zn/ZnSO4 and Cu/CuSO4 cell.
1. It is a device for converting chemical energy into electrical energy. It means spontaneous redox reaction is used for the production of electric current. This cell was prepared by L.Galvani and A.Volts, hence named as Galvanic or Voltaic Cell.
2. It consists of two half-cells. Each half cell consists of an electrodes and the solution with which it is in contact.
3. Example: Daniel Cell-Zn/ZnSO4 and Cu/CuSO4 cell.
Short Brief | Glossary | Ninth Class Chemistry Notes
Acidity
The acidity of a base is defined as the number of ionizable hydroxyl groups in its molecule.
Anode
It is an electrode through which electrons enter the external circuit.
Alpha Rays
There are positively charged particles emitted from a radioactive substance. They carry two positive charges and are called helium nuclie.
Analytical Chemistry
It is the branch of chemistry which discusses the analytical methods forgetting information about chemical compounds and chemical processes.
Atomic Number
Number of positively charged particles (protons) present in the nucleus of an atom.
Atomic Size
Average distance between the nucleus of an atom and its outermost electronic shell. Its units are nm or pm.
Arrehenius Acid
It is a chemical compound which gives proton (H+) in water.
Arrehenius Base
It is a chemical compound which gives hydroxide ion (OH-) in water.
Atomic Spectrum
Spectrum of radiations emitted by the excited atoms when they come to the normal state.
Acidic Salts
An acidic salt is obtained when hydrogen atoms present in an acid, are partially replaced by metallic atoms.
Alchemist
A scientist trying to convert cheaper metals into precious metals is called Alchemist and this branch of chemistry is called Alchemy.
Atomic Mass
The mass of an element relative to the unit mass, which is 1/12th o the mass of C-12.
Ampere
The amount of electric current which liberate one electrochemical equivalent of a substance per second during electrolysis of that substance is called ampere.
Biochemistry
It is the study of chemical compounds present in living things.
Balancing of Chemical Equations
Equating the atoms of reactants with those of products.
Beta Rays
These are electrons emitted from a radioactive substance.
Brownian movement
The free movement of the molecules of gases and liquids is called Brownian movement.
Bronsted Acid
A compound which can donate proton.
Bronsted Base
A compound which can accept proton.
Basicity
The basicity of an acid is defined as the number, of ionizable hydrogen atoms present in its molecule.
Basic Salts
A basic salt is obtained when the hydroxyl groups present in a base are partially replaced by some other groups.
Boiling Point
A temperature at which a liquid changes into gaseous state.
Chemistry
The branch of science, which deals with the composition of matter changes in matter and the laws or principles which govern these changes.
Chemical Equation
The representation of a chemical change in terms of symbols and formulas.
Covalent Solid
A solid in which there exist a covalent bond between atoms.
Covalent Bond
It is the force of attraction that arises between two atoms due to mutual sharing of an electron pair.
Co-Ordinate Covalent Bond
When the shared pair of electrons is provided by one of the bonded atoms, a coordinate covalent bond is formed.
Cohesive Forces
The forces of attraction present between the particles of solid, liquid and a gas.
Cathode Rays
Rays emitted from cathode in the discharge tube.
Colloidal Solution
A solution in which solute particles are bigger than those present in a true solution and which cannot be filtered.
Conductor
A substance which allows electric current to pass through it.
Cathode
It is an electrode through which electrons leave the external circuit.
Concentration of a Solution
The amount of a solute which has been dissolved in a particular amount of a solvent.
Concentrated Solution
A solution, which contains an excess amount of a solute as compared to that of a solvent.
Cell
The vessel containing reacting substances in which transfer of electrons takes place is called cell.
Coulomb
It is unit of electric current. When one ampere electric current is passed for one second the quantity of electric current is one coulomb.
Discharge Tube
A glass tube containing a gas at a very low pressure and provided with electrodes to study the passage of electricity through the gas.
Dipole-Dipole Forces
The forces of attraction which originate due to the difference in electro negativities of the bonded atoms in polar molecules.
Diffusion
The movement of molecules from a higher concentration to a Lowr concentration is called Diffusion.
Dilute Solution
A solution, which contains a small amount of a solute as compared to that of a solvent.
Double Salts
When two typical salts are crystallized together a double salt is formed. The physical properties of the crystals of double salt are different from those of the component salts.
Doberiner’s Law of Triads
Dobereiner arranged similar elements in sets of three, called Triads. Atomic mass of the middle atom of a triad was equal to the average of the atomic masses of first and third members.
Degree of Ionization
It is the extent to which an electrolyte ionizes in water.
Experiment
An experiment is an activity performed under suitable conditions with specially designed instruments to get the required information.
Empirical Formula
The formula of a compound which shows the minimum ratio present between the atoms.
Electron Affinity
The amount of energy given out when an electron is absorbed in the outermost electronic shell of all isolated gaseous atom. Its units are KJ/mol.
Electro-Negativity
It is the power of an atom to attract the shared pair of electrons.
Evaporation
The continuous escape of the molecules of a liquid from its surface.
Elastic Collision
When gas molecule collides with each other their total energy does not decrease or increase. This type of collision is called an elastic collision.
Electrolytic-Cell
In a non-spontaneous oxidation-reduction reaction takes place with the help of electrical energy.
Electro-Chemistry
It is that branch of chemistry in which chemical energy is converted into electrical energy or electrical energy is converted into chemical energy.
Electrolytes
When electricity is passed through an ionic compound which is either in the fused state or in the form of aqueous solution, it is decomposed into its constituents. The ionic compound is called an electrolyte.
Electrolysis
The passage of electricity through an electrolyte is called electrolysis.
Electrochemical Series
A list of ions in which they are arranged in the order of their ability to get discharged.
Electroplating
The process of depositing a metal on another metal with the help of electricity.
Exothermic Reaction
Those chemical reactions during which heat is evolved.
Endothermic Reactions
Those chemical reactions in which heat energy is absorbed.
Enthalpy of Reaction
Heat of reaction which takes place at constant pressure.
Formula Mass
Formula mass is the mass of compound relative to the unit mass which is 1/12th of the mass of C-12.
Farad
It is the unit of charge 1 farad = 96500 coulomb.
Fusion
When a solid change into liquid this phenomena is called Fusion.
Heat of Neutralization
The heat given out during a neutralization reaction is called heat of neutralization.
Heat of Reaction
Heat evolved or absorbed during a chemical reaction which takes place at pressure.
Hypothesis
In the light of experiments, the scientists try to explain observations and facts. This tentative explanation is called hypothesis. It is quite possible that after sometime, on the basis of new experiments this hypothesis may be rejected.
Hydrogen Bonding
When a hydrogen atom is attached to any one of fluorine, oxygen and nitrogen atoms, there appears strong dipole forces which are called hydrogen bonding.
Hydrated Ions
Ions of a solute surrounded by water molecules are called hydrated ions.
Ionization
An electrolyte splits up into charged particles upon heating or in its aqueous solution. This process is called Ionization.
Ionic Theory
A theory which explains the process of electrolysis.
Intermolecular Forces
The forces of attraction present between the molecules of a compound.
Ionization Energy
The minimum amount of energy required to remove an electron from the outermost electronic shell of an isolated gaseous atom. Its unit is KJ/mol.
Ionic Bond
A bond formed due to the electrostatic force of attraction between oppositely charged ions.
Ionic Solid
A solid which is made up of ions of opposite charges.
Isotope
Atoms of an element having the same atomic number but different mass number.
Inorganic Chemistry
The study of all elements and their compounds except carbon is called inorganic chemistry.
Industrial Chemistry
The application of chemical knowledge in technology and industry and the preparation of industrial products are called industrial chemistry.
Inference
To deduce results after coordinating the observed facts with integrated scientific knowledge is called inference.
Kinetic Theory
The theory which explains the composition and properties of all the three states of matter.
Lewis Acid
A substance which can accept an electron pair.
Law
A theory when repeatedly gives the same results after experimentation and offers correct explanation of scientific facts it then becomes a law or principle.
Law of Conservation of Mass
Total mass of reactants is equal to that of products during a chemical reaction.
Law of Definite
A compound always contains elements combined together in a fixed ratio by mass.
Law Multiple Proportions
When two elements combine together to give more then one compounds, the different masses of an element, which combine with the fixed mass of the other element, have a simple ratio between them.
Law of Reciprocal Proportions
When two or more elements A and B combine separately with the fixed mass of the third element E the ratio in which they do so may be the same or some simple multiple of the ratio in which these two elements (A and B) combine with each other.
Molar Solution
A solution in which one mole of a solute has been dissolved in one dm3 of solution. It is represented as M.
Metallic Bond
When positively charged metal ions are held together by freely moving electrons, the bond formed is called a metallic bond.
Molecular Solid
A solid which has Vander Waal’s forces present between its molecules.
Melting Point
A temperature at which a solid changes into a liquid.
Mass Number
The total number of protons and neutrons present in the nucleus of an atom.
Mendeleyv’s Periodic Law
Properties of elements are a periodic function of their atomic masses.
Modern Periodic Law
Properties of elements are a periodic function of their atomic numbers.
Molecular Mass
Molecular mass is the mass of an element or a compound relative to the unit mass, which is 1/12th of the mass of C-12.
Molar Mass
The mass of an element or a compound which contains Avogadro’s number particles.
Molecular Formula
The formula of an element or a compound which tells the actual number of atoms present in the molecule of that element or a compound.
Neutralization
Acids and bases react together to form salts and water and in this way they neutralize the properties of each other. This reaction is called Neutralization reaction.
Normal Salts
Salts, which neither have replaceable hydrogen atoms nor hydroxyl groups.
Non-Conductor
A substance through which electric current cannot pass.
Neutron
It is the smallest neutral particle present in the nucleus of atoms. Its mass is slightly more than that of a proton.
Nucleus
Central part of an atom where most of its mass is concentrated. Its size is very small as compared to the size of the atom.
Newland’s Law of Octaves
If elements are arranged in the increasing order of their atomic masses every 8th element repeats the properties of the 1st element.
Oxidation
A chemical reaction in which oxygen is added or hydrogen is removed or electrons are lost.
Octet Rule
When an atom has eight electrons in its outer most shell, its is said to be stable and does not combine with other atom to reduce its energy. This is called octet rule.
Organic Chemistry
The branch of chemistry in which we study the compounds of carbon.
Observation
The process of observing natural phenomena with the help of five senses and the scientific equipment.
Orbits
The circular path of an electron around the nucleus.
pH Scale
The negative log of hydrogen ion (H+) concentration present in a solution is called pH. This scale measures the concentration of hydrogen ions present in a solution.
Percentage by Mass
Volume of a solute present in 100cm3 of a solution.
Percentage by Volume
Volume of a solute present in 100 cm3 of a solution.
Physical Chemistry
The branch of chemistry, which deals with the physical properties and physical behaviour of material things.
Prediction
The inference based on observed facts.
Proton
It is the smallest positively charged particle present in all kind of atoms. The mass of this particle is equal to the mass of the hydrogen nucleus (H+).
Positive Rays
Rays produced in the discharge tube, which are traveling in a direction opoposite to the cathode rays.
Reversible Reaction
Chemical reaction, which takes place both directions, forward as well as backward.
Reduction
A chemical reaction in which hydrogen is added or oxygen is removal or electrons are absorbed.
Radioactive Rays
Rays emitted from radioactive element or their compounds, which can cause fogging of the photographic plate.
Strong Acid
An acid which ionizes completely in water.
Strong Base
A base which can ionize completely in water giving excess of hydroxide ions.
Sublimation
Some solids, upon heating, change directly into vapors instead of changing into liquid.
Scientific Method
The method which helps to collect facts on the basis of observations and experiments. Theories and laws are then formulated to explain these facts.
Solute
The substance present in relatively lesser amount in a solution.
Solvent
The substance present in excessive amount in a solution.
Solvated Ions
Ions of a solute surrounded by solvent molecules in a solution are called solvated ion.
Saturated Solution
A solution, which contains the maximum amount of a solute at a particular temperature and which is unable to dissolve further amount of solute in it.
Supersaturated Solution
A solution which contains an amount of solute more than that required for the preparation of a saturated solution at a particular temperature.
Standard Solution
A solution whose concentration is known.
Solubility
The amount o solute in grams which can dissolve in 100 gm of solvent at a particular temperature to give a saturated solution.
Suspension
A mixture in which solute particles do not dissolve in solvent.
Strong Electrolytes
An electrolyte which completely ionize in water.
Transition Elements
Elements having incomplete penultimate (next inner to the outermost) electronic shell.
Theory
If a hypothesis is accepted (after discussion and experimentation) it is called a theory.
Thermo Chemistry
It is the branch of chemistry in which we study the heat changes during a chemical reaction.
Unsaturated Solution
A solution, which can dissolve further amount of a solute at a particular temperature, is called unsaturated solution.
Unified Atomic Mass Unit
Unit of a new scale, which is equal to 1/12th of the mass of C-12.
Voltaic Cell
In a cell a spontaneous oxidation-reduction reaction is used to produce electric current.
Weak Electrolyte
An electrolyte which undergoes partial ionization in water.
Weak Base
A base which ionizes partially in water.
Weak Acid
An acid which ionizes partially in water.
Water of Crystallization
The number of water molecules present in the crystals of a solid.
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