Chemistry For Class IX - Chapter No.1 - Questions And Answers

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Chapter No.1: Introduction To Chemistry
Questions And Answers















DEFINITION OF CHEMISTRY:
 “The branch of Natural science which deals with the study of composition,"
OR
 "properties, structure, changes and the laws governing the changes that occurring inside the matter is called Chemistry.”

MATTER:
Anything having mass and occupy space is known as Matter.
There are three commonly known states of matter. According to latest Information there are four states of matter
1. Solid
2. Liquid
3. Gas
4. Plasma (newly discovered fourth state of matter but not known commonly)

LANDMARKS IN THE HISTORY OF CHEMISTRY

THE GREEK PERIOD:

Famous Greek philosophers:
Plato (347-428 B.C)
Aristotle (322-384 B.C)
Democritus (357-460 B.C)
  • "They introduced the concept of element, atom and chemical reactions."
  • "They thought that all matter was derived from four elements earth, air, fire and water."
  • "These elements have properties of their own such as dry, hot, cold and wet."
  • "According to them, fire was hot and dry, earth was cold and dry, water was cold and wet and air was hot and wet."

Romans

  • "The Romans developed the chemical arts still further: - They improved the metallurgical processes and introduced the enameling of pottery. However, they developed little theoretical knowledge in this regard. Their works were all empirical."


THE MUSLIM PERIOD:

The Muslim period was from 600 to 1600 A.D in the history of chemistry and is known as period of alchemist.
The modern scientific knowledge is based on the contribution of these Muslim scholars.

Jabir-Ibne-Hiyan(721-803 A.D):
He is generally known as the father of alchemy (founder of Chemistry).
 Achievements:

  1. He invented experimental methods for preparation of Nitric acid, Hydrochloric acid and sulphuric acid."
  2. He discovered white lead.
  3. He also developed methods for the extraction of metals from their ores.
  4. He also developed methods of dyeing clothes.
  5. He developed method of distillation.
  6. He also developed many laboratory apparatus.


Al Razi (862-930 A.D):
Al Razi was a physician, chemist (at that time they were known as alchemist) and a philosopher.
Achievements:

  1. He was an expert surgeon and was the first to use opium as anesthesia.
  2. He divided the substances into living and non-living origins, which was later adopted by Berzelius, in 1806 to classify chemical compounds on the basis of their origins as organic and inorganic compounds.
  3. Al-Razi prepared ethyl alcohol by the fermentation of sugar.

 Al-Beruni(973-1048 A.D):
Contributed a lot in physics, metaphysics, mathematics, geography and history. In the field of chemistry, he determined the densities of different substances.

Ibne-Sina(980-1037):
Ibne-Sina was famous for the contribution in the field of medicines, medicinal chemistry, philosophy, mathematics and astronomy.

DIRECTION OF RESEARCH OF MUSLIM SCIENTISTS: -

  • "These Muslim alchemists were interested more in finding a way to prolong life and to convert base metals like lead, copper into gold but they could not do so."
  • "Their researches led to the discoveries of many substances and laid the foundation of chemistry. Many important reagents like sulphuric acid, Nitric acid, Hydrosulphyuric acid, Silver nitrate etc were discovered."
  • "Chemists of that period, however, devoted their energies mainly to the production of drugs for the use of medicines."


 THE MODERN PERIOD (FROM 1600 A.D AND ONWARD):

NAME OF SCIENTISTS CONTRIBUTION IN CHEMISTRY:
1. ROBERT BOYLE (1627-1691):
He is affectionately known as the father of modern chemistry and was the first to put forward the idea that chemistry should be regarded as a systematic investigation of nature with the sole aim of promoting knowledge. As a result, lots of discoveries were made during later years.
2. J.BLACK (1728-1799): He made a study of Carbon dioxide.
3. J.PRIESTLY (1733-1804): He discovered Oxygen, Sulphur dioxide and Hydrogen chloride.
4. SCHEELE (1742-1786): He discovered Chlorine.
5. CAVENDISH (1731-1810): He discovered Hydrogen.
6. LAVOISIOR (1743-1794): He discovered that oxygen constituted about one fifty of air.
7. GAY- LUSSAC (1778-1850): He discovered relationship between volume of given mass of a gas and temperature.

CHEMISTRY AND SOCIETY 

SIGNIFICANT REASONS TO STUDY CHEMISTRY (Importance of chemistry):
There are three significant reasons to study chemistry.

  1. Chemistry has important practical application in the society. The development of life saving drugs is one and a complete list would touch upon the most areas of modern chemistry.
  2. Chemistry is an Intellectual enterprise, a way of explaining our material world.
  3. Chemistry figures prominently in other fields, such as in biology in the advancement of medicines."    

EXAMPLES OF CHEMICAL SUBSTANCES USED IN DAILY LIFE:
Use of chlorine and fluorine in daily life:
Chlorine:

  • It is used in making poly vinyl chloride (PVC) as plastic pipes. 
  • Other chlorine compounds are used as bleaching agent, disinfectants, solvents, pesticides, refrigerants, flame retardant and drugs.
  • It is used in treating water to kill pathogenic (disease causing) organism.
  • In this way the disease like Cholera, Typhoid, Fever and Dysentery are dangerous disease are all eliminated from most of the part of the world.


Fluorine:

  • It is used in compounds like sodium fluoro phosphate and NaF (sodium fluoride) in our toothpastes to protect and control tooth decay. 
  • It is great advantage of chemistry on the society.


BRANCHES OF CHEMISTRY

1. PHYSICAL CHEMISTRY:
The branch of chemistry which deals with the laws and the principles governing the combination of atoms and molecules in chemical reaction and study of physical properties of matter is called PHYSICAL CHEMISTRY.

2. ORGANIC CHEMISTRY:
The branch of chemistry which deals with the study of Hydrocarbon and their derivatives with the exception of CO2, CO, metal carbonates Bicarbonates and carbides is known as ORGANIC CHEMISTRY.

3. INORGANIC CHEMISTRY:
The branch of chemistry which deals with the study of chemistry of elements and their compounds, generally obtained from non-living organism, i.e. from minerals is known as INORGANIC CHEMISTRY.

4. ANALYTICAL CHEMISTRY: The branch of chemistry which deals with the study of the methods and techniques involved to determine the kind, quality of various components in a given substance is known as ANALYTICAL CHEMISTRY.

5. BIOCHEMISTRY: The branch of chemistry which deals with the study of compounds chemical reaction involves in living organism i.e. plants and animals and their metabolism in the living body is known as BIOCHEMISTRY.
6. INDUSTRIAL OR APPLIED CHEMISTRY: The branch of chemistry which deals with the study of different chemical processes involved in the chemical industries for the manufacturing of synthetic products like glass, cement, paper, soda asli, fertilizers, medicines etc. is known as INDUSTRIAL CHEMISTRY.

7. NUCLEAR CHEMISTRY: The branch of chemistry which deals with the study of changes occurring in the nuclei of atoms, accompanied by the emission of invisible radiations is known as NUCLEAR CHEMISTRY.

8. ENVIRONMENTAL CHEMISTRY:
The branch of chemistry which deals with the study of the interaction of chemical materials and their effects on the environment of animals and plants is known as ENVIORMENTAL CHEMISTRY.

9. POLYMERIC CHEMISTRY:
The branch of chemistry which deals with the study of polymerization and the product obtained through the process of polymerization such as plastic, synthetic fibers, paper etc. is known as POLYMERIC CHEMISTRY.

THE SCIENTIFIC APPROACH IN CHEMISTRY

Science has developed through series of discoveries from many years which started off as observed natural phenomenon which had to be explained. This was done by using scientific method in a systematic manner.
SCIENTIFIC METHOD:
There are four main stages of scientific method:

  1. Observation.
  2. Hypothesis
  3. Theory
  4. Scientific Law of principle


1. OBSERVATION:
 "Observation is a basic tool to elaborate a phenomenon varies from person to person and depends upon person’s own skills and elaboration.”
Different people observe a phenomenon in different ways. Some of us observe something very critically to extract from it a new point. Observation of a thing is one of the scientific approaches in chemistry.

2. HYPOTHESIS:
“The explanation obtained by the pondering of a scientist after observing a phenomenon which is still on a trial is called Hypothesis.”
When a phenomenon is observed, a scientist ponders over it and" "carries out relevant experiments. He sieves through the data and arrives at a possible explanation for the nature of the phenomenon. This explanation, which is still only a trial is called hypothesis. It may or may not undergo a change which results further investigations and accumulation of more knowledge or facts.

3. THEORY:
“The Hypothesis which is supported by a large number of different types of observations and experiments given by many scientists is known as Theory.”
The scientist conveys his hypothesis to other workers of the same "fields for the discussion and for further experimentation. When the hypothesis is supported by a large amount of different types of observation and experiments, then it becomes a theory i.e. scientifically acceptable idea or principle explain a phenomenon. A good theory predicts new facts and unravels new relationship between occurring phenomenon.

4. SCIENTIFIC LAW OR PRINCIPLE:
“A theory which is tested again and again and found to fit the facts and from which valid predictions maybe made is then known as scientific law or principle.”
Science cherishes all form of ideas and proposals. Even obsolete "(outdated) ideas are kept as reference. It is said that there is no end to knowledge, so development in science too may have no limits."


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