Fundamentals of Chemistry | Chapter # 1 | Chemistry Class 9th

Science; The knowledge that provides understanding of this world and how it works is called science. Q: 01: Define Chemistry. Ans: The branch of science which deals with composition, structure, properties and reactions of matter is called chemistry. The useful aspects of chemistry are following:- (i) Petrochemical products. (ii) Soap and detergents. (iii) Medicines and drugs. (iv) Papers and plastics. Q: 02: Write the names of branches of Chemistry. Ans: (i) Physical Chemistry (ii)Organic Chemistry (iii)In-organic Chemistry (iv)Bio-Chemistry (v)Industrial Chemistry (vi) Nuclear Chemistry (vii) Environmental Chemistry (viii) Analytical Chemistry. Q: 03: What is Physical Chemistry? Ans: The branch of chemistry that deals with physical properties of matter and its composition is called physical chemistry. For example: To determine melting and boiling point, study the effect of temperature or radiation on matter. Q: 04: Define Organic Chemistry. Ans: The branch of chemistry that deals with study of hydrocarbons and their derivates is called organic chemistry. Example: Study of petroleum and its products. Q: 05: 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. Example: The study of soap, glass, cement etc. Q: 06: 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. Example: Study of photosynthesis and respiration in living things. Similarly the effect of medicine and food are discussed in this branch of chemistry. Q 07: Define Industrial Chemistry? Ans: The branch of chemistry that deals with the manufacturing of chemical compounds on commercial scale is called industrial chemistry. Example: The Study of manufacturing of industrial products such as sugar, paints and soap etc. Q: 08: Define Nuclear Chemistry? Ans: The branch of chemistry that deals with properties of radioactivity and nuclear reactions is called nuclear chemistry. Example: The preservation of food and generation of electrical power through nuclear reactor are discussed in this branch of chemistry. Q: 09: Define Analytical Chemistry. Ans: The branch of chemistry that deals with analysis of a sample to identify its components is called analytical chemistry. Example: Determination of nitrogen in urea and clinical analysis of blood etc. Q: 10: 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. Example: Study of industrial pollution and its effects on ecosystem. Q: 11: What is Matter? Ans: Anything that has mass and occupies space is called matter. Example: Our body and all things around us. It has three physical states (i) Solid (wood, stone) (ii) Liquid (water, milk) (iii) Gas (air, oxygen, CNG) Q: 12: Define Substance. Ans: Piece of matter in pure form is called substance. Every substance has fixed composition and properties. It cannot be divided in to small pieces by physical methods. For example; Water, Carbon. Q: 13: What are the physical properties? Ans: The properties that are associated with physical state of a matter are called physical properties. For example; Color, smell, melting point, boiling point. When ice is heated it melts to water and water is further heated it boils to steam. In this process physical state of water changes but chemical composition remain the same. Q: 14: What are Chemical properties? Ans: The properties which are associated with chemical composition of matter are called chemical properties. For example; rusting of iron, decomposition of water. 2H2O 2H2 + O2