PURE SUBSTANCES
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This document defines pure substances and mixtures. A pure substance is homogeneous and has definite properties, while a mixture contains two or more substances mixed together without chemical change. Solutions are homogeneous mixtures where particle size is molecular. Suspensions are heterogeneous mixtures where particle size is larger, allowing settling. Colloids have intermediate particle sizes that do not settle. The document discusses types of mixtures and their distinguishing characteristics.
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PURE SUBSTANCES
- 1. PURE SUBSTANCE A homogeneous material which contains particles (atoms or molecules ) of only one kind and has a definite set of properties( melting point , boiling point) and which cannot be separated into other kinds of matter by any physical process. eg:-Elements : Metals and Non-metals , Compounds : Salts. .
- 2. MIXTURE When two or more substances (elements ,compounds or both) are mixed together in any proportion, such that they do not undergo any chemical change but retain their individual characteristics , the resulting product is a mixture.
- 3. Types of Mixtures Homogeneous mixture:- A mixture in which different constituents are mixed uniformly and there are no specific boundaries seen between the particles of the mixture is called a Homogeneous mixture. Eg: Solutions such as common salt in water , sugar in water etc are homogeneous mixtures .Similarly alloys such as brass, bronze, etc. are homogeneous solid -solid solutions of metals. Heterogeneous mixture:- A mixture in which different constituents are not mixed uniformly and there are specific boundaries seen between the particles of the mixture is called a heterogeneous mixture . Eg: Mixture of sand and salt, iron and sulphur powder, soil etc are egs. of such mixtures.
- 4. Mixed salad
- 5. Homogeneous mixture:- milk , Soft drink
- 8. SOLUTION A homogeneous mixture of two or more substances is called a solution . A true solution is one which the particles of the solute are broken down to such a fine state( molecular level) that they cannot be seen under a powerful microscope.
- 9. SOLUTIONS • When the 2 substances totally mix it is called a solution. • E.g. Solute + Solvent = Solution • (sugar) + (water) = Solution • • • We then say sugar is soluble in water, it has dissolved. •
- 10. Components of a solution Solvent:-the component which dissolves the other component in itself. Usually it is the larger component. Examples :-water in a solution of water and copper suphate, turpentine oil in paints. Solute:-Component which dissolves in the
- 12. CHARACTERISTICS OF SOLUTIONS A true solution is always clear and transparent. It is homogeneous in nature. The solute particles break down to almost molecular size (Diameter=10-9 m or 1nm). It is stable and solute particles do not separate or settle down on standing. It cannot be separated by filtration. Solute can be recovered by evaporation or crystallization methods.
- 13. SUSPENSIONS • A heterogeneous mixture of in solution particles of solute , spread throughout a solvent is called a suspension. • Eg: Muddy water, slaked-lime suspension (used for white washing), white paints (particles of dye suspended in turpentine oil)
- 14. SUSPENSIONS• Suspensions • Sometimes when we mix substances they stay in clusters. We therefore say it is insoluble in water. • E.g. Chalk + Water = Suspension • • Eventually the particles sink to the bottom to form sediment. •
- 15. Characteristics of suspensions It is opaque and does not allow light to pass through it. Particle size is more than 10-5 cm in diameter. It is heterogeneous in nature. It is unstable and the suspension particles settle down when allowed to stand undisturbed. Particles can be separated by filtration method from the solvent.
- 16. Colloid A heterogeneous solution in which particle size is between 10-7 cm to 10 5‑ in diameter, such that the solute particles neither dissolve nor settle down in a solvent is called a colloidal solution. eg. jelly, mist, soap solution, blood.
- 18. CHARACTERISTICS OF COLLOIDS Colloidal solutions are translucent in nature. The particle size is between 10-7 cm and 10-5 cm in diameter. They are heterogeneous in nature (but appear to be homogeneous). They are stable and solute particles do not separate on standing. The particles cannot be separated by filtration method. Particles can be separated by centrifugation method.
- 19. Passage of light through solution,suspension and colloid.
- 21. TYNDALL EFFECT The phenomenon due to which the path of light becomes visible, due to scattering of light by the colloidal particles.
- 22. Tyndall effect
- 23. JOHN TYNDALL • HE WAS A BRITISH PHYSICIST WHO WAS AN AVID PROMOTER OF SCIENCE IN THE VICTORIAN ERA. • BORN IN 1920 IN IRELAND.
- 26. Dispersing medium (external phase) - the constituent found in the greater extent in the colloid. Dispersed phase (internal phase) - the constituent found in the lesser extent. If water is the dispersing medium, it is often known as a hydrosol.
- 27. Type of colloid Dispersion medium Dispersed phase Example AEROSOL Gas Liquid Fog , Clouds ,Mist AEROSOL Gas Solid Smoke , automobile exhaust FOAM Liquid Gas Shaving cream FOAM solid Gas Foam rubber, sponge SOL liquid Solid Milk of magnesia SOLID SOL Solid Solid Coloured gems stone , Milky glass EMULSION Liquid Liquid Milk , Face cream GEL solid Liquid Jelly , Cheese , Butter
- 28. AEROSOL Gas Liquid Fog , Clouds ,Mist clouds mist fog
- 29. AEROSOL Gas Solid Smoke , automobile exhaust smoke Car exhaust
- 30. FOAM Liquid Gas Shaving cream Shaving cream foam
- 31. FOAM solid Gas Foam rubber, sponge Foam rubber sponge
- 32. SOL liquid Solid Milk of magnesia Milk of magnesia
- 33. SOLID SOL Solid Solid Coloured gems stone , Milky glass Gem stones Milky glass
- 34. EMULSION Liquid Liquid Milk , Face cream milk Face cream Emulsion paints
- 35. GEL solid Liquid Jelly , Cheese , Butter Jelly Butter Cheese
- 36. Assessment Questions: • Multiple Choice Questions • 1. What factor distinguishes a suspension from a colloid? a) light reflects off the particles of a suspension b) the particles of a suspension will sink out if left over time to rest c) suspensions are clear d) suspensions cannot be filtered
- 37. 2. An example of an emulsifying agent would be__ a) oil b) soap c) water d) salt
- 38. 3. An example of a homogeneous mixture is___ a) sand and water b) flour and water c) salt dissolved in water d) oil and water
- 39. 4. Which statement is not true. a) particles in a colloid will reflect light b) the particles of a solution are molecular in size c) a suspension can be filtered d) a solution can be filtered
- 40. • 5. An emulsion is always between___ a) Two solids b) A solid and liquid c) Two gases d) Two liquids