9th Is Matter Around Us Pure-1.pdf

Is Matter Around Us Pure Pure substances: A pure substance is one which is made up of only one kind of particles. These may be atoms or molecules and can’t be separated by any physical method for example water, sulphur, hydrogen, carbon etc. are know as pure substances because they are made up of o...

Is Matter Around Us Pure Pure substances: A pure substance is one which is made up of only one kind of particles. These may be atoms or molecules and can’t be separated by any physical method for example water, sulphur, hydrogen, carbon etc. are know as pure substances because they are made up of only one kind of particles.A pure substance has a fixed composition as well as a fixed melting point and boiling point Impure Substances: An impure substances is that which made by two or more than two different kinds of particle (atoms or molecules) and can be separated by physical method. All the mixtures are impure substances. Some of the examples of the mixtures are: salt solution, sugar solution, milk, sea-water, air, sugarcane juice, soft drinks, sharbat, rocks, minerals, petroleum, LPG, biogas, tap water, tea, coffee, paint, wood, soil and bricks. A mixture may be homogeneous or heterogeneous. A mixture does not have a fixed composition or a fixed melting point and boiling point. Mixture 1)Mixtures refer to those substances which consist of two or more elements or compounds, mixed together in any ratio and do not give rise to new compound. For example: sea water, air, chocolate milk etc. 2)Mixture is composed of two or more substances mixed together in any ratio i.e. the composition is variable and do not possess properties like fixed melting or boiling point. 3)Mixture shows the properties similar to that of its constituents and they can be separated by using physical and chemical methods. Types of mixtures: 1) Homogeneous mixtures 2) Heterogeneous mixture Homogeneous mixtures: Such mixtures have only one phase. They have the same composition throughout and there is no visible separation of line between the constituents. For example: sugar solution, vinegar etc. Heterogeneous mixture: Mixtures which has more than one phase is known as heterogeneous mixture. There is a visible boundary of separation between the components and they do not have the same composition throughout. Type of homogeneous mixture 1) Solid homogeneous mixture (alloys) 2) Liquid homogeneous mixture (solution of alcohol in water) 3) Gaseous homogeneous mixture (air). Type of heterogeneous mixture 1) Solid heterogeneous mixture (mixture of sand and sugar) 2) Solid-liquid heterogeneous mixture (solution of chalk in water) and 3) Gaseous heterogeneous mixture (smoke in air). Substance – Cannot be separated into its constituent particles by any physical process Solution – Homogeneous mixture of two or more substances Alloys – Homogeneous mixture of metals Solution The component of the solution that dissolves the other component in it is called solvent (present in larger amount). The component of the solution that is dissolved in the solvent is called solute (present in lesser quantity). Properties of solution 1) Homogeneous mixture 2) Particles are extremely small, not visible to the naked eye 3) Light path not visible 4) Solute particles cannot be separated by filtration Some formula for concentration Suspension 1) Heterogeneous mixture of solids and liquids 2) Solid particles suspend throughout the medium Properties of suspension 1) Heterogeneous mixture 2) Particles visible by the naked eye 3) Light path visible 4) Particles settle down 5) Solute particles can be separated by filtration Ex- sand in water COLLOIDS Colloid is a kind of solution in which the size of solute partials is intermediate between those the true solutions and those are in suspension. Colloidal solutions are also heterogeneous in nature like suspensions, but they have smaller size of the particles, which are distributed. It ranges between 1 nm to 100 nm i.e., in between the particles size in true solution and suspension. Since the particles sizes are close two what we notice in solutions most of the colloidal solutions appear to be homogeneous like true solutions. But actually these are not. We come across a large variety of the colloidal solutions in daily life. Smoke coining out of the chimneys of factories, tooth paste, ink, blood, soap solutions, jellies, starch solution in water are a few common examples. We have stated earlier that the colloidal solutions are the heterogeneous mixtures. This means that, the constituents are not present in a single phase. Actually there are two phases in a colloidal solution. These are known as dispersed phase and dispersion medium. Example – milk, rubber Having dispersed phase and dispersion medium Properties of Colloidal solution 1) Heterogeneous mixture 2) Particle size is small, not visible to the naked eye 3) Light path can be visible 4) Particles do not settle down 5) Substances cannot be separated by filtration 6) Colloidal solutions are a two phase system 7) Colloidal particles carry charge 8) Particles in a colloidal solution follow zigzag path  9) Tyndall effect Classification of Colloids(type of Colloidal solution) (i) Sol (ii) Solid sol (iii) Aerosol (iv) Emulsion (v) Foam (vi) Solid foam (vii) Gel Tyndall effect – Scattering of the light beam by suspended particles in the solution Evaporation – For mixture of volatile solvents and non-volatile solutes Centrifugation – Cream from milk In dairies and homes for separation of butter from milk For drying wet clothes Used in diagnostic laboratory for blood and urine test. Some process of separating the components of mixture 1) Evaporation:The salt is separated from seawater by using the process called evaporation. Evaporation is the process in which the liquid changes its state to a gas at any temperature below its boiling point. 2) Filtration:The process which is used to separate a solid substance from a liquid by allowing the liquid substance to pass through the filtering medium is called filtration. In the process of filtration, the liquid is allowed to pass through the filter paper attached to a funnel. The liquid will pass through the paper while the solid will remain on the filter paper. 3) Centrifugation:Centrifugation is the technique in which the mixture is separated through spinning and the denser particles are forced to the bottom while the lighter particles stay at the top when spun rapidly. 4) Separating funnel:The immiscible liquids can be separated by using a separating funnel. The principle used in separating the funnel is based on the difference in densities of the two liquids. The denser liquid is settled at the bottom of the funnel, while the lighter liquid will remain at the top. 5) Sublimation:The process in which the solid-state changes its state directly to a gas without converting it into liquid is called sublimation. This process is generally used to separate sublimable volatile components from non sublimable impurities. Ammonium chloride, iodine, naphthalene, dry ice, arsenic, etc are examples of  sublimable solid which changes their state from solid to gas without leaving any residue. 6) Chromatography:Chromatography is the technique used for the separation of those solutes that dissolve in the same solvent. It works on the principle of interaction between the solute and solvent. The compound which is more soluble in the solvent can elute faster while the compound which has low solubility in the solvent will elute slower. 7) Distillation:Distillation is the method for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient differences in their boiling points. It is commonly used in water purification techniques. 8) Fractional distillation is the type of distillation process in which the chemical mixture into different fractions using the difference in their boiling point. It is useful for liquids whose difference in boiling point is less than 25K. The liquid which has a low boiling point separates first from a mixture while the liquid which has the highest boiling point will separate last.. 9) Crystallisation:The process in which the large crystal of pure substances formed from their solution is called crystallization. It is used to separate crystals of alum (phitkari) from impure samples. Pure substance can be classified as elements or compounds. Element: The basic form of matter that cannot be broken down into simpler substances by chemical reactions’. Elements can be further classified as metals, non-metals, metalloids and noble gases. Compound: Compounds are formed when two or more elements combine chemically in a fixed proportion. Chemical Change Changes which involve a change in the chemical composition of a substance, undergoing the change Formation of one or more new substances takes place during a chemical change. Most chemical changes can not be reversed easily. The chemical composition of the substance undergoing a chemical change does not remain the same. Chemical changes are always accompanied by a change in energy. What is chemical formula? A chemical formula is a symbolic representation of a chemical compound. It tells us about the type and number of atoms present in the compound. For example, the chemical formula of common salt is NaCl. It tells us that NaCl is composed of 1 atom of Sodium (Na) and 1 atom of Chlorine (Cl)