NCERT SOLUTION CLASS 9 CHAPTER 2 (IS MATTER AROUND US PURE )  PAGE NO. 15 QUESTION NO. 1 What is meant by substance ? ANSWER NO. 1 A pure substance consist of single type of particle. It is a pure single form of matter. It has definite properties and composition. Example - Iron. QUESTION NO. 2 List the points of differences between homogeneous and heterogeneous mixtures. ANSWER NO. 2 HOMOGENEOUS MIXTURE Particles are uniformly distributed throughout the mixture. It has a uniform composition. Components cannot be separated easily. Example - Solution of sugar and alloys. HETEROGENEOUS MIXTURE All the particles are completely mixed and can be distinguished with the eye or under a microscope. It has a irregular composition. Components can be separated easily. Example - Mixture of sand and common salt, mixture of sand and water.                               ...

NCERT SOLUTION SCIENCE CLASS 9 CHAPTER 1 ( MATTER IN OUR SURROUNDINGS) PAGE -3 QUESTION No 1      Which of the following are matter?     Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume. ANSWER       SOLID STATE:       Chair and almond.    LIQUID STATE:      Cold drink    GASEOUS STATE :  Air and smell of perfume QUESTION NO 2:        Give reason for the following observation:   The smell of hot sizzling food reaches you several meters away,but to get the smell from cold food you have to go close. ANSWER:        Solids diffuses at a very slow rate. But if the temperature of a solid is increased then the particle of solids moves faster due to increased kinetic energy and thus diffusion of the solid particle increased in air. Hence .the smell of hot sizzling food reaches us even at a dis...