class 9 notes

Structure Of The Atom Class 9 CBSE Notes - Chapter 4 Essentially, the structure of an atom comprises of protons, neutrons and electrons. These basic components provide the mass and charge of the atoms. The nucleus comprises of proton and neutron, with the electron orbiting around that. Introduction to Structure of an Atom Atoms Atoms are the building blocks of matter. It is the smallest unit of matter that is composed of three sub-atomic particles: the proton, the neutron, and the electron. Cathode ray experiment J. J. Thomson discovered the existence of electrons. He did this using a  cathode ray  tube, which is a vacuum-sealed tube with a  cathode  and anode on one end that created a beam of electrons travelling towards the other end of the tube. The air inside the chamber is subjected to high voltage and electricity flows through the air from the negative electrode to the positive electrode. The characteristics of cathode rays (electrons) do not depend upon the ma...

Is Matter Around Us Pure Class 9 Notes - Chapter 2 We do know that matter is made up of particles which are arranged in a certain way. Gases particles are well separated and can freely move about, solids, on the other hand, have particles that are tightly packed, usually with no scope to move around. Purity Pure substances Pure substances  are elements or compounds. They are made up of only one kind of entity. They cannot be broken down into simpler entities by chemical or physical methods. They have a fixed composition. Example : Diamond, carbon dioxide. Mixtures Mixtures  are formed by just mixing two or more pure substances (components) such that each substance retains its own chemical identity. Types of mixtures Types: 1. Homogeneous mixture A mixture which has a uniform composition throughout is called a  homogeneous mixture or solution. Examples:  sugar in water, salt in water. Heterogeneous mixture A mixture which contains physically distinct pa...

Matter In Our Surroundings Class 9 Notes - Chapter 1 States of Matter Note:  As per the revised CBSE curriculum, this chapter has been removed from the syllabus for the 2020-21 academic session. Matter can be classified as solid, liquid and gas on the basis of interparticle forces and the arrangement of particles. These three forms of matter are interconvertible by increasing or decreasing pressure and temperature.  For example, ice can be converted from solid to a liquid by increasing the temperature. Property  Solid Liquid Gas Shape and volume Fixed shape and volume No fixed shape but has volume Neither definite shape nor volume Energy Lowest Medium Highest Compressibility Difficult Nearly difficult Easy Arrangement of molecules Regular and closely arranged Random and little sparsely arranged Random and more sparsely arranged Fluidity Cannot flow Flows from higher to lower level Flows in all directions Movement Negligible Depends on interparticle attraction Free, c...

Atoms and molecules are responsible for forming tiny sand particles, gargantuan black holes and everything in between. The atom is the most fundamental unit of matter, making up everything that we see around us. It is extremely small, measuring in at less than 0.1 to 0.5 nanometers. Laws of Chemical Combination Chemical Reactions In a chemical reaction, two or more molecules interact to produce new compounds and are called reactants, whereas the newly formed compounds are called products. In a chemical reaction, a chemical change must occur, which is generally observed with physical changes like precipitation, heat production, colour change etc. Law of conservation of mass According to the law of conservation of mass, matter can neither be created nor destroyed in a chemical reaction. It remains conserved. Mass of reactants will be equal to the mass of products. Law of constant proportions A pure chemical compound contains the same elements combined together in a fixed proportion by ma...