CH#1 Short Questions 9th Class

Chapter # 01
Q: 01: Define Chemistry.

Ans: The branch of science which deals with composition, structure, properties and reactions of matter is called
chemistry.
Q: 02: What is Physical Chemistry?
Ans: The branch of chemistry that deals with physical properties of matter and composition is called physical
chemistry.
Q: 03: Define Organic Chemistry.
Ans: The branch of chemistry that deals with study of hydrocarbons and their derivatives is called organic
chemistry.
Q: 04: Define In-organic Chemistry.
Ans: The branch of chemistry that deals with study of all elements and their compounds
except hydrocarbons compounds is called in-organic chemistry.
Q:05: Define Bio-Chemistry.
Ans: The branch of chemistry that deals with study of structure, composition, and chemical reactions in living
organisms is called bio-chemistry.
Q 06: Define Industrial Chemistry?
Ans: The branch of chemistry that deals with the manufacturing of chemical compounds on commercial scale is
called industrial chemistry.
Q: 07: Define Nuclear Chemistry?
Ans: The branch of chemistry that deals with properties of radioactivity and nuclear reactions is called nuclear
chemistry.
Q: 08: Define Analytical Chemistry.
Ans: The branch of chemistry that deals with analysis of a sample to identify its components is called analytical
chemistry.
Q: 09: Define Environmental Chemistry.
Ans: The branch of chemistry that deals with study of environmental components and the effects of human
activities on the environment is called environmental chemistry.
Q: 10: What is Matter?
Ans: Anything that has mass and occupies space is called matter.
Q: 11: What are the physical properties?
Ans: The properties that are associated with physical state of a matter are called physical properties.
Q: 12: What are Chemical properties?
Ans: The properties which are associated with chemical composition of matter are called chemical properties.
Q: 13: Define Element.
Ans: It is a substance made up of same type of atoms, having same atomic number.
Q: 14: What is Symbol?
Ans: The abbreviated name of an element is called symbol.
Q: 15: Explain Valency.
Ans: The combining capacity of an element with other elements is called valency.
Q: 16: What is Comppund? Give example.
Ans: A substance which is made up of two or more elements chemically combined together in a fixed ratio by
mass is called compound.
Q: 17: Define mixture by example.
Ans: A substance which is made up of two or more elements physically combined together without fixed ratio by
mass is called misture.
Q: 18: Define Atomic Number or Proton Number?
Ans: The number of protons present in the nucleus of an atom is called atomic number or proton number.
Q: 19: Define Mass Number or Nucleon Number.
Ans: The sum of number of neutrons and protons present in the nucleus of an atom is called mass number.
Q: 20: Explain relative Atomic Mass?
Ans: The average relative mass of an atoms of an element as compared to 1/12 th mass of carbon-12 are called
relative atomic mass.
Q: 21: What is Atomic Mass unit?
Asn: The mass equal to 1/12th of the mass of a carbon -12 is called atomic mass unit. It is unit of atomic mass.
Q: 22: How to write a Chemical Formula?
Ans: Symbol of positive radical is written at left side while negative radical symbol is written at right side. The
valency of both radicals is written at lower right corner by cross exchange method.
For example; Na+1 CI-1 = Na1, Cl1 = NaCl
Q: 23: Explain Empirical Formula with example.
Ans: The formula which shows simplest whole number ratio of atoms present in a compound is called empirical
formula.
For example; empirical formula of benzene is CH.
Q: 24: Explain Molecular formula:
Ans: The formula which shows actual numbers of atoms of each element present in compound is called molecular
formula.
For example; molecular formula of benzene is C6H6.
Q: 25: Define Molecular Mass.
Ans: The sum of atomic masses of all the atoms present in one molecule of a molecular compound is called
molecular mass.
Q: 26 Explain Formula Mass.
Ans: It is the sum of atomic masses of all the atoms present in one formula unit of a substance.
Q: 27: What is Molecular lon? Explain with example.
Ans: When a molecule loses or gains electrons, it forms a molecular ion. It has positive or negative.
For example CH4.
Q: 28: What is Molecule? Give an example.
Ans: The smallest particle of substance which can exist freely is called molecule.
For example. H2
Q: 29: Explain Homo-atomic Molecule.
Ans: A molecule containing same type of atoms is called homo-atomic molecule.
For example: H2, Cl2, O3
a) Monoatomic molecule:
A molecule consisting of only one atom is called monoatomic molecule.
For example Na, C.
b) Poly atomic molecule:
A molecule consisting of many atoms is called poly atomic molecule.
For example O3, Sg.
Q: 30: Explain Hetero-atomic molecule.
Ans: A molecule containing different kinds of atoms is called hetero-atomic molecule.
For example: HCl, Ca0 etc.
Q: 31: Define Gram Atomic Mass?
Ans: The atomic mass of an element expressed in gram is called gram atomic mass
Q: 32: What is Gram Molecular Mass?
Ans: The molecular mass of a compound expressed in gram is called gram molecular mass.
Q: 33: What is Gram Formula Mass? Give example.
Ans: The formula mass of an ionic compound expressed in gram is called formula mass
Q: 34: Explain Avogadro's number.
Ans: The numbers of atoms, molecules, or ions in one mole of a substance is called Avogadro's number.
For Example; One mole of carbon atom=6.02×10 23
Q: 35: What is Mole?
Ans: The atomic mass, molecular mass or formula mass of substance expressed in grams is called mole.
Q: 36: What is Molar Mass?
Ans: The average mass of substance of one mole is called molar mass.
Q: 37: What is significance of symbol of an element?
Ans. Symbols are used for elements instead of writing of their complete names. It is short to write and element can
be recognized easily.
For example symbol of hydrogen is H. Symbol of sodium is Na.
Q: 38: What is Atom?
Ans: It is the smallest particle of an element which may or may not exist freely.
Q: 39: What is Ion?
Ans: Atom or group of atoms having a charge is called ion
Q: 40: Define cation.
Ans: An atom or group of atom having positive charge is called cation.
Q: 41: What is Anion?
Ans: An atom or group of atom having negative charge is called anion.
Q: 42: What is Molecule.
Ans: The smallest particle of substance which can exist freely is called molecule
Q: 43: Give the scope of Bio-chemistry?
Ans. It covers all chemical processes taking place in living organisms such as synthesis and Metabolism of
macromolecules like carbohydrates proteins and fats.

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Chapter # 01

Q: 01: Define Chemistry.

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