Mixtures And Their Separations

Mixtures and their separations Janadi Gonzalez-Lord

2 Prepared by JGL 8/9/2009 Table of contents • Syllabus requirements • Pure and impure substances • Classification of mixtures • Separation of mixtures • Types of separation techniques • Experiments • Industrial uses • Separating mixtures in everyday life

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4 Prepared by JGL 8/9/2009 Syllabus requirements - Mixtures a) differentiate between mixtures and compounds in terms of composition and formation b) recognize that the components of mixtures can be separated by simple means c) define the terms : miscible , immiscible , soluble , insoluble , heterogeneous , homogenous , and apply them correctly i.e. miscible refers to liquids , soluble to gases and solids d) identify mixtures as solutions , suspensions , colloids , emulsions based on the states of matter present and their solubility / miscibility e) define solute and solvent f) identify dissolving as one substance fitting in between the spaces of another substance . g) identify a method of separating mixtures based on their composition h) describe the separating methods of simple distillation , fractional distillation , filtration , layer separation i) draw line diagrams for the methods in (h)

5 Prepared by JGL 8/9/2009 Syllabus requirements - Mixtures j. carry out filtration and layer separation in the laboratory and write up notes about the procedure and results k. recognize that filtration separates particle based on size l. Identify sieving , sifting and straining as everyday methods of filtration m. observe the set up as a teacher demonstration the simple distillation process n. identify other methods of separation such as chromatography , centrifugation , solvent extraction o. suggest methods for separating mixtures based on the properties of their components e.g. sand and salt p. name two industrial methods of separating mixtures e.g. fractional distillation used to obtained distilled spirits , centrifugation used to separate components of blood / body fluids in laboratory testing , filtration in purification of domestic water supply

7 Prepared by JGL 8/9/2009 Matter can be sub-divided into PURE and IMPURE SUBSTANCES or MIXTURES. PURE substances can be sub-divided into ELEMENTS and COMPOUNDS IMPURE substances or MIXTURES can be sub-divided into HOMOGENOUS and HETEROGENOUS

8 Prepared by JGL 8/9/2009 Can be separated into Can be Can be separated separated into into Source: www.mghs.sa.edu.au/Internet/Faculties/Science/Year10/Pics/elementsAndCompounds.gif

9 Prepared by JGL 8/9/2009 Elements versus compounds An element.... A compound...... • consists of only one kind of • consists of atoms of two or atom more different elements • cannot be broken down into a bound together, simpler type of matter by • can be broken down into a either physical or chemical simpler type of matter means (elements) by chemical means • can exist as either atoms (e.g. (but not by physical means), argon) or molecules • has properties that are (e.g., nitrogen). different from its component elements, • always contains the same ratio of its component atoms

10 Prepared by JGL 8/9/2009 An element Consists of only one kind of atom Ar Ar can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen). cannot be broken down into a simpler type of matter by either physical or chemical means N N If you try to break apart an atom or molecule, you get an ATOMIC BOMB N N

11 Prepared by JGL 8/9/2009 H H A compound O consists of atoms of two or more different elements bound together always contains the same ratio of its component atoms H H O Water (formula H2O) For every water molecule, there are 2 Hydrogen atoms for every 1 Oxygen H H O O H H atom O has properties that are different from its H H component elements O For example, hydrogen and oxygen are gases but water is a liquid H H O

12 Prepared by JGL 8/9/2009 Examples of elements and compounds Elements Compounds Source: www.physicalgeography.net/fundamentals/images/compounds_molecules.jpg

13 Prepared by JGL 8/9/2009 Compounds versus Mixtures A mixture.... Remember that a compound... • consists of two or more • consists of atoms of two or different elements and/or more different elements compounds physically bound together, intermingled • can be broken down into a • can be separated into its simpler type of matter components by physical (elements) by chemical means means, and (but not by physical means), • often retains many of the • has properties that are properties of its components. different from its component Syllabus requirement met: elements, differentiate between mixtures and • always contains the same ratio compounds in terms of composition and of its component atoms formation

14 Prepared by JGL 8/9/2009 A mixture can be... A mixture of different A mixture of different A mixture of different types of atoms and types of atoms types of molecules molecules N N N N O O H H H H Cl H

15 Prepared by JGL 8/9/2009 Match the following 1. Pure elements Answer: A, C, D 2. Elements made of SINGLE ATOMS Answer: A, D 3. An element made of MOLECULES Answer: C 4. Mixture of TWO elements Answer: E, F 5. Mixture of THREE elements Answer: H 6. Pure compounds Answer: G 7. Mixture of TWO compounds Answer: B

17 Prepared by JGL 8/9/2009 Mixtures can be...... Homogeneous Heterogeneous • The prefixes "homo"- indicate • The prefixes: "hetero"- sameness indicate difference. • A homogeneous mixture has • A heterogeneous mixture the same uniform appearance consists of visibly different and composition throughout. substances or phases. • Many homogeneous mixtures • The three phases or states of are commonly referred to as matter are gas, liquid, and solutions. solid. Syllabus requirements met: define the terms : heterogeneous , homogenous and apply them correctly

18 Prepared by JGL 8/9/2009 Example of homogeneous mixtures Some mixtures around us are things we don't even think of as mixtures. Vinegar is a homogeneous mixture of water and acetic acid (CH3COOH). Most commercial vinegars have an acetic acid content of about 5%. Acetic acid gives vinegar its characteristic odor.

19 Prepared by JGL 8/9/2009 Example of heterogeneous mixtures The combination of oil and vinegar in salad dressing is a common example of a HETEROGENEOUS mixture. Here the two layers are distinctly visible. Each layer by itself is considered a HOMOGENEOUS mixture.

20 Prepared by JGL 8/9/2009 Mixtures can be same phase..... Liquid + Liquid Solid + Gas + Solid Gas Mixtures

21 Prepared by JGL 8/9/2009 Or Mixtures can be mixed-phase Solid + Gas Solid + Liquid Liquid + Gas Mixtures

22 Prepared by JGL 8/9/2009 Gas + Gas • Example: Air ( Gas + Liquid N2, O2 , Ar, CO2 • Example: , other gases) Carbonated beverages (CO2 Liquid + in water) Liquid Solid + Liquid • Example: gasoline (a • Example: Sea mixture of water ( NaCl and hydrocarbon other salts in compounds) water) Solid + Solid + Gas Solid • Example: H2 in • Alloys – Homogeneous platinum or palladium mixtures of Mixtures metals • Example : brass (Cu/Zn)

23 Prepared by JGL 8/9/2009 Liquid + Liquid • EMULSION Solid + Liquid • Example: milk • SUSPENSION: Examples: Tomato juice, jello, blood • COLLOIDS: Example: glue, paint Solid + Solid Solid + Gas • Example : Gravel (sand, clay and small • Example: Smoke rocks) (Air and carbon particles) Heterogeneous Mixtures

24 Prepared by JGL 8/9/2009 Liquid-Liquid solutions Example: Example: Example: Oil and water Phenol and water Ethanol and water Partially Immiscible Miscible miscible Syllabus requirement met: define the terms : miscible , immiscible , and apply them correctly i.e. miscible refers to liquids Increasing mixability

25 Prepared by JGL 8/9/2009 Syllabus requirement met: identify mixtures as solutions , suspensions , colloids , emulsions Heterogeneous mixtures based on the states of matter present and their solubility / miscibility Solute does not fully dissolve in Solution <Solute particle Liquid + liquid solvent size< Suspension Will separate into Solute particles are clearly Solute particles do not immiscible liquids ONLY if visible settle out on standing no stabiliser added Solute particles settle out upon Solute particles can pass standing through filter paper Suspensions Colloids Emulsions Increasing solute particle size

26 Prepared by JGL 8/9/2009 Solutions Solute Solvent Solution homogeneous mixture substance in The substance which the which is being solute is dissolved dissolved Syllabus requirement met: Define solute and solvent

27 Prepared by JGL 8/9/2009 DECREASING SOLUBILITY

28 Prepared by JGL 8/9/2009 Table salt dissolving in water Dissolving. When a solute dissolves in a solvent, the particles of the solute fit in between the particles of the solvent. There is no chemical reaction. The change is reversible and the essential components of the mixture remains the same. Syllabus requirement met: Identify dissolving as one substance fitting in between the spaces of another substance .

30 Prepared by JGL 8/9/2009 A mixture of different Separate atoms and types of atoms and molecules molecules N N N N O O Can be separated by O O O O PHYSICAL MEANS into N N

32 Prepared by JGL 8/9/2009 SUBLIMATION SOLVENT • One substance EXTRACTION sublimes, the other • Differing solubilities does not in a particular solvent • Example: • Example: Iodine + Ammonium chloride sodium chloride + sodium chloride Solid + solid mixtures

33 Prepared by JGL 8/9/2009 FRACTIONAL SEPARATING DISTILLATION FUNNEL • Miscible • Immiscible • Slightly differing • Differing densities boiling points • Example: Oil + water • Example: Ethanol + water Liquid + liquid mixtures

34 Prepared by JGL 8/9/2009 SOLUTIONS • EVAPORATION/ CRYSTALLIZATION • Widely differing boiling points • Example: Copper sulphate + water SUSPENSION • SIMPLE DISTILLATION COLLOIDS • DECANTATION. • Different particle size. • Widely differing boiling points • CHROMATOGRAPHY • Example – chalk + water • Differing solubilities in a particular solvent leading to differing speeds of • FILTRATION. movement on • Different particle sizes. chromatogram • Example: screened methyl orange Solid + Liquid mixtures

35 Prepared by JGL 8/9/2009 Solvent extraction Are the components ionic, covalent or Determinating the correct mixed? Does on the Yes components Sublimation sublime? Are the components in the mixture Do they have Yes Fractional miscible? differing boiling distillation separation technique points? Do they have Yes What is the state of Separating funnel matter of differing densities? components in mixture? Decantation Do the components have widely differing particle sizes? Filtration Is the mixture a Evaporation & solution, suspension crystallization or colloid Do the components have widely differing boiling points? Syllabus requirement met: Simple distillation identify a method of separating mixtures based on their Chromatography composition

36 Prepared by JGL 8/9/2009 Experiments demonstrating the different methods of separating mixtures

37 Prepared by JGL 8/9/2009 Experiment 1 Question: You have a mixture of sodium chloride and ammonium chloride. How would you separate them?

38 Prepared by JGL 8/9/2009 Solvent extraction Are the components ionic, covalent or mixed? Does on the Yes components Sublimation sublime? Determining the correct Are the components in the mixture Do they have Yes Fractional miscible? differing boiling distillation separation technique points? Do they have Yes What is the state of Separating funnel matter of differing densities? components in mixture? Decantation Do the components have widely differing particle sizes? Filtration Is the mixture a Evaporation & solution, suspension crystallization or colloid Do the components have widely differing boiling points? Simple distillation Chromatography

39 Prepared by JGL 8/9/2009 Materials: •Glass funnel, evaporating dish, Bunsen burner, heating stand •10g of NH4CL & NaCl mixture •Place a small amount of the mixture in the evaporating dish. •Place glass funnel over dish. Method: •Light bunsen burner until a small even flame is produced. •Continue heating until no more ammonium chloride is deposited on the funnel. Results & •White solid (ammonium chloride) will be deposited on the upper Observations: sides of the funnel •The mixture contained 2 ionic solids one of which sublimes (goes Analysis & from solid to gas) on heating. •The change is reversible so when the gaseous ammonium chloride Conclusion: comes into contact with the cooler surface of the glass funnel it returns to the solid state. Sublimation

40 Prepared by JGL 8/9/2009 Experiment 2 Question: You have a mixture of sodium chloride and iodine crystals. How would you separate them?

42 Prepared by JGL 8/9/2009 • Two (2) 100 ml beakers, glass stirring rod, evaporating dish, Bunsen burner, heating stand, filter paper, funnel Materials: • 10g of iodine crystals (I2) & sodium chloride (NaCl) mixture • 10 ml of 1,1,1-trichloroethane •Place 10g of the mixture in beaker. •Add 10ml of 1,1,1-trichloroethane to beaker. •Stir with glass stirring rod until all iodine crystals are dissolve Method: •Fold filter paper into glass funnel. Filter beaker with NaCl, I2 and solvent mixture into second beaker. •Light Bunsen burner until a small even flame is produced. •Heat second beaker with I2/solvent solution until all solvent evaporates. •Allow residue to cool •On adding the 1,1,1-trichloroethane, the mixture separates into two layers. Results & •The top layer is brown in colour. This contains iodine in solution. •The second layer is a suspension of NaCl in solvent. Observations: •White crystals are left as filtered residue in filter paper. The filtrate is a brown solution •On heating, and crystallization, brown crystals are left Analysis & •The mixture contained one ionic compound (NaCl) which dissolves only in polar solvents such as water and one molecular compound (i2) which only dissolves in organic solvents. Conclusion: •The 2 components could therefore be separated by dissolving the molecular compound in the organic solvent, filtering off the ionic compound and recrystallizing the molecular compound. Solvent extraction

43 Prepared by JGL 8/9/2009 Sodium chloride (NaCl) is ionic and therefore only dissolves in polar Solvent extraction solvents Sodium chloride (NaCl (s)) Iodine (I2) is a covalent compound and therefore dissolves in organic solvents Add 1,1,1- Filter off Mixture of trichloroethane Iodine solution NaCl (s) iodine + (organic solvent) sodium chloride sodium chloride Iodine & solvent filtrate Evaporate the solvent through slow heating Syllabus objective Iodine crystals Cool & met: crystallize identify other methods of separation such as solvent extraction

44 Prepared by JGL 8/9/2009 Experiment 3 Question: You have a solution of copper (II) sulphate and water. How would you separate them?

46 Prepared by JGL 8/9/2009 Materials: •Round bottom flask, thermometer, Bunsen burner, heating stand, Leibig condenser, Erlynmeyer flask •10ml of copper (II) sulphate solution - Cu(SO4) (aq) •Place 10 ml of CuSO4 (aq) into round-bottom flask. Method: •Set up the equipment as shown in diagram •Light Bunsen burner until it achieves a steady blue flame. •Heat solution steadily until the temperature reaches just above 100 °C. •Continue to heat until all the solution turns to blue crystals. Results & •The volume of the solution decreases and changes state (from liquid to solid blue crystals). Observations: •A clear solution forms in the Erlenmeyer flask over time. Analysis & •The boiling point of water is 100°C while that of CuSO4 is 150°C. •By keeping the temperature just above 100°C but below 150°C, the water in the solution changes state from liquid to gas (water vapour). Conclusion: •The water vapour travels through the Leibig condenser which cools the temperature and causes the water to vapour to change back to its liquid state as this is a reversible change. •The CuSO4 remains in the round bottomed flask as its boiling point has not been reached. Syllabus requirement met: describe the separating methods of simple distillation Simple distillation

47 Prepared by JGL 8/9/2009 Thermometer Heating wire pad Round bottom flask Water out Bunsen Leibig condenser burner Water in Erlynmeyer flask Heating stand Syllabus requirement met: Draw line diagrams for simple distillation Source: www3.moe.edu.sg/edumall/tl/digital_resources/chemistry/images/simple_distillation2.jpg

48 Prepared by JGL 8/9/2009 Experiment 4 Question: You have a solution of ethanol and water. How would you separate them?

50 Prepared by JGL 8/9/2009 • Round bottom flask, thermometer, Bunsen burner, heating stand, heating Materials: pad Leibig condenser, Erlynmeyer flask, fractionating column • 20ml of ethanol and water solution (50/50 W/V) •Place 20 ml of solution into round-bottom flask. •Set up the equipment as shown in diagram Method: •Light Bunsen burner until it achieves a steady blue flame. Heat solution steadily until the temperature reaches 80°C. •Continue to heat until all there is no more increases in the volume of distillate collected in the Erlenmeyer flask Results & • The volume of the solution decreases by approximately 50% • A clear solution forms in the Erlenmeyer flask over time which is Observations: approximately 50% of the original volume. •The boiling point of water is 100°C while that of ethanol is 78.4°C. Analysis & •By keeping the temperature just above 78°C but below 100°C, the ethanol in the solution changes state from liquid to gas. •The ethanol vapour travels through the fractionating column, where it is repeated cooled Conclusion: and reheated as it falls back into the base of the column, removing impurities. •The vapour then passes through the Leibig condenser which cools the temperature and causes the water to vapour to change back to its liquid state as this is a reversible change. •The water remains in the round bottomed flask as its boiling point has not been reached. Fractional distillation Syllabus requirement met: describe the separating methods of fractional distillation

51 Prepared by JGL 8/9/2009 Heat is applied to the bottom of the larger round bottom flask that holds the Fractional distillation apparatus fermented mixture. As the vapors rise in the fractionating column, the higher boiling point water condenses and falls back into the round bottom flask. The ethanol continues to rise slowly and reaches the distillation head where a thermometer registers its temperature. If the temperature is kept at about 78 C, by adjusting the heat, ethanol will flow over to the Liebig condenser and turned back into a liquid. The Liebig condenser has a cold water jacket wrapped around a central tube and when the hot ethanol vapor comes in contact with the walls of the inner tube, it loses heat and returns to a liquid state. The condensed ethanol drips down and is collected in the smaller round bottom flask. Source: www.chemistrydaily.com/chemistry/upload/1/16/Fractional_distillation_lab_apparatus.png

52 Prepared by JGL 8/9/2009 Experiment 5 Question: You have a solution of oil and water. How would you separate them?

54 Prepared by JGL 8/9/2009 • Separating funnel, clamp stand, Erlynmeyer flask Materials: • 20ml of oil and water mixture (50/50 W/V) •Set up the equipment as shown in diagram •Place 20 ml of solution into separating funnel Method: •Allow the mixture to settle then slowly release valve and allow the bottom layer to flow out into the flask below. •Close valve when the last drop of the bottom layer has been released into flask. Results & • The mixture separates into 2 distinct layers. Observations: Analysis & • Water has a higher density than oil. It therefore sinks to the bottom of the separating funnel. • The two components are highly immiscible, that is they do not mix well with Conclusion: each other and form a distinctly visible phase boundary between the two upon settling which allows the easy separation using just the human eye. Separating funnel Syllabus requirement met: describe the separating methods of layer separation

55 Prepared by JGL 8/9/2009 Set up of separating funnel apparatus Results of experiment

56 Prepared by JGL 8/9/2009 Experiment 6 Question: You have a mixture of sand and water. How would you separate them?

58 Prepared by JGL 8/9/2009 • 100ml beaker, 50 ml beaker, glass stirring rod Materials: • 30ml of sand and water suspension (50/50 W/V) •Place mixture into 50 ml beaker •Allow to stand until the sand settles to bottom and the mixture looks fully Method: transparent. •Pour the mixture slowly into the 100 ml beaker. Use the glass stirring rod to prevent any of the sand sediment from being poured into the beaker. Results & • The mixture went from opaque to transparent with Observations: white sediment settling to the bottom upon standing. • The sand and water mixture formed a suspension. The solute, sand, could not completely mix with the water, i.e. It was partially insoluble. Analysis & • The sand particles settled to the bottom as it was denser than water and insoluble. Conclusion: • The separation of the two components after standing (this process is known as sedimentation) can be done using just the eye as the separation is very distinct. However, there is a possibility that some sand particles are left in the beaker. Decantation

59 Prepared by JGL 8/9/2009 Decantation Sedimentation Decantation Source: www.tutorbene.com/cms_images/decantation.bmp

60 Prepared by JGL 8/9/2009 Experiment 7 Question: You have a solution of table salt and water. How would you retrieve the salt from the solution?

62 Prepared by JGL 8/9/2009 Materials: • Evaporating dish, heating pad, heating stand, Bunsen burner • 20ml of salt and water solution (50/50 W/V) •Place solution into evaporating dish •Set up apparatus as shown in diagram. Method: •Light Bunsen burner and heat solution slowly, starting with a low flame and gradually increasing the heat. •Continue heating until all liquid evaporates. •Turn off Bunsen burner. Allow residue to cool. Results & • All water evaporates. Observations: • The solution gradually turns to solid crystals. • The water in the solution reaches its boiling point and chnages state from Analysis & liquid to gas (water vapour). • NaCl is an ionic solid which has a very high boiling point as compared to water and remains in the solid state. Conclusion: • This method is only useful for separating the mixture’s components when the solvent (in this case water) is not to be retrieved at the end of the experiment. Evaporation/ crystallization

63 Prepared by JGL 8/9/2009 Evaporation and crystallization Salt water solution Evaporating dish Heating pad or wire gauze Heating stand or tripod Bunsen burner Source: www3.moe.edu.sg/edumall/tl/digital_resources/chemistry/images/evaporation.jpg

64 Prepared by JGL 8/9/2009 Experiment 8 Question: You have a solution of chalk and water. How would you retrieve both components of the mixture?

66 Prepared by JGL 8/9/2009 Materials: • Filter paper, funnel, 100 ml beaker, Erlenmeyer flask • 30ml of chalk and water solution (50/50 W/V) •Place mixture into 100 ml beaker •Fold filter paper as shown in diagram below •Place in funnel then place funnel into Erlenmeyer flask Method: •Pour mixture into funnel slowly until the entire mixture is transferred without spilling out of funnel. •Allow the mixture to separate out completely before removing the filter paper. Results & • The chalk remains as residue on the filter paper Observations: • The water comes out in the Erlenmeyer flask • The chalk and water mixture formed a suspension. The solute, chalk, could not completely mix with the water, i.e. It was partially insoluble. Analysis & • The chalk particles are larger than the water molecules and cannot pass through the porous filter paper. Conclusion: • The water molecules are small enough to pas s through the filter paper. • This difference in particle size allows the chalk to be separated from the water via the process of filtration. Syllabus requirement met: 1. describe the separating methods of filtration 2. carry out filtration in the laboratory and write up notes about the procedure and results 3. recognize that filtration separates particle based on size Filtration

67 Prepared by JGL 8/9/2009 Procedure for fluted filter paper This is used when you need to get faster filtration. Source: www.theresasakno.com/popup/popup.asp?sid=D674F0CE-C7CB-4A46-94EA-1E79AD64C378&imgname=034.jpg

68 Prepared by JGL 8/9/2009 Water molecules Beaker Filter paper Filter paper Mixture of chalk and water (suspension) Chalk particles The water molecules Beaker are smaller than the Water chalk particles. They are small enough to pass through the pores of the filter paper. Funnel Source: www3.moe.edu.sg/edumall/tl/digital_resources/chemistry/images/filtration.jpg

69 Prepared by JGL 8/9/2009 How to filtrate a hot solution Materials required: 1. Clamp stand, 2. Short stem glass funnel 3. Glass stirring rod 4. Filter paper (fluted) 5. Erlenmeyer flask 6. Cloth A filtration procedure called "hot gravity filtration" is used to separate insoluble impurities from a hot solution. Hot filtrations require fluted filter paper and careful attention to the procedure to keep the apparatus warm but covered so that solvent does not evaporate Source: www.chemistry.mcmaster.ca/~chem2o6/labmanual/expt1/exp1-f3.gif

70 Prepared by JGL 8/9/2009 Vacuum Filtration Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure. Vacuum filtration uses either a Buchner or a Hirsch funnel. Vacuum filtration is faster than gravity filtration, because the solvent or solution and air is forced through the filter paper by the application of reduced pressure. The reduced pressure requires that they be carried out in special equipment: 1. Buchner or Hirsch funnel 2. heavy-walled, side arm filtering flask 3. rubber adaptor or stopper to seal the funnel to the flask when under vacuum 4. vacuum source Source: http://blog.khymos.org/wp-content/2007/09/stock-filtration.png

71 Prepared by JGL 8/9/2009 Experiment 9 Question: How would you separate the pigments in screened methyl orange?

73 Prepared by JGL 8/9/2009 • Chromatography paper,, glass rod, beaker Materials: • 5ml screened methyl orange, 50ml water •Screened methyl orange is dissolved in water and carefully spotted onto chromatography paper •Alongside it are spotted known colours on a 'start line' •The paper is carefully dipped into water, which is absorbed into the Method: paper and rises up it. •The distance moved by the solvent is marked on carefully with a pencil and the distances moved by each 'centre' of the coloured spots is also measured • Two different colours appear on the chromotogram at different points Results & on the paper. • Rf = distance moved by dissolved substance (solute) / distance moved Observations: by solvent. • The Rf value is calculated for each spot. Analysis & • Due to different solubilities and different molecular 'adhesion' some colours move more than others up the paper, so effecting the Conclusion: separation of the different coloured molecules. Syllabus requirement met: Chromatography identify other methods of separation such as chromatography

74 Prepared by JGL 8/9/2009 These are the pigments Chromatography present in the dye The material to be separated e.g. a food dye (6) is dissolved in a solvent and carefully spotted onto chromatography paper sheet. Alongside it are spotted known colours on a 'start line' (1-5). The paper is carefully dipped into a solvent, which is absorbed into the paper and rises up it. The solvent may be water or an organic liquid like an alcohol (e.g. ethanol) or a hydrocarbon, so-called non- aqueous solvents. For accurate work the distance moved by the solvent is marked on carefully Any colour which horizontally matches with a pencil and the distances moved by another is likely to be the same molecule each 'centre' of the coloured spots is also i.e. red (1 and 6), measured. These can be compared with brown (3 and 6) and known substances BUT if so, the blue (4 and 6) match, identical paper and solvent must be used showing these three are all in the food dye (6).

75 Prepared by JGL 8/9/2009 Methods used in industry for separating mixtures

76 Prepared by JGL 8/9/2009 Chromatography Calculation of Rf values The distance a substance moves, compared to the distance the solvent front moves is called the reference or Rf value 0.0<Rf<1.0 where Rf = 0.0 (not moved - no good) Rf = 1.0 (too soluble - no good either) Rf ratio values between 0.1 and 0.9 can be useful for analysis and identification. distance distance moved by moved by Rf dissolved solvent substance (solute) Chromatography can be used to separate the amino acids in proteins and to separate drugs in pharmaceutical laboratories

77 Prepared by JGL 8/9/2009 Centrifugation is a process that involves the use of the centrifugal force for the separation of mixtures, used in industry and in laboratory settings. More-dense components of the mixture Centrifugation migrate away from the axis of the centrifuge, while less-dense components of the mixture migrate towards the axis. Increasing the effective gravitational force on a test tube causes the precipitate to gather on the bottom of the tube. The remaining solution is properly called the "supernate" .The supernate is then either quickly decanted from the tube without disturbing the precipitate, or withdrawn with a pipette Source: http://www.freewebs.com/ltaing/centrifuge2.gif

78 Prepared by JGL 8/9/2009 Centrifugation is used to separate the components in blood Centrifugation of blood A centrifuge separates out blood components by their various densities. The red blood cells (RBCs) are denser and move to the bottom of the tube. The plasma fraction is the least dense and will float as the top layer. The "buffy coat" which contains the majority of platelets will be sandwiched between the plasma and above the RBCs. Syllabus requirement met: Name two industrial methods of separating mixtures - centrifugation used to separate components of blood / body fluids in laboratory testing

79 Prepared by JGL 8/9/2009 Fractional distillation in industry Continuous fractionating How it works column This is an industrial fractionating column separating a feed stream into one distillate fraction and one bottoms fraction. However, many industrial fractionating columns have outlets at intervals up the column so that multiple products having different boiling ranges may be withdrawn from a column distilling a multi-component feed stream. The "lightest" products with the lowest boiling points exit from the top of the columns and the "heaviest" products with the highest boiling points exit from the bottom.

80 Prepared by JGL 8/9/2009 Fractionating columns in industry Bubble cap trays in How it works fractionating columns Bubble-cap "trays" or "plates" are one of the types of physical devices which are used to provide good contact between the up- flowing vapour and the down- flowing liquid inside an industrial fractionating column Syllabus requirements met: Name two industrial methods of separating mixtures e.g. fractional distillation used to obtained distilled spirits

81 Prepared by JGL 8/9/2009 Manufacture of rum and spirits Rum is distilled from the fermented products of sugar cane, usually molasses. As is the case with all distilled spirits, rum is water white when first distilled. Amber and dark coloured rums obtain their colour from caramel and the extractives from the oak barrel during ageing. Fermentation: Fermentation is the process by which the sugar in molasses is converted into ethyl alcohol by the action of yeast. Distillation: Distillation is the process of boiling a liquid and condensing its vapour to produce another liquid. Still Distillation: There are two (2) different styles used. Rum produced by Wooden Continuous Still distillation Rum produced by Copper Pot Still distillation Blending Blending is an art form, and the Master Blender uses several different types and styles of rum to create a brand in much the same way that an artist uses different colours to create a painting. Ageing and Cooperage Rum ages best in oak barrels that have been charred on the inside, and that nature does not allow for short cuts in the ageing process. The cooperage, is the area where the ageing barrels are assembled before filling. Soruce: http://woodsrum.co.uk/images/process_large.gif

82 Prepared by JGL 8/9/2009 Filtration in industry Syllabus requirements met: name two industrial methods of separating mixtures e.g. filtration in purification of domestic water supply Water purification plant Rapid sand filtration First, to quickly remove the impurities from the raw water, a coagulant is added, forming the impurities into large clumps that settle to the bottom. After this process, the water passes through a coarse sand layer in a filter bed, which cleanly removes the impurities. This method is effective even when the raw water is relatively turbid, and can be used to treat large amounts of water using only a small area of land.

84 Prepared by JGL 8/9/2009 Sieving is used in several ways Coarse-sieving threshed rice Definition Separation of a mixture of various-sized particles, either dry or suspended in a liquid, into two or more portions, by passing through screens of specified mesh sizes. Source: http://www.ucl.ac.uk/archaeology/staff/profiles/fuller/baligang /baligang-hand-sieve.jpg

85 Prepared by JGL 8/9/2009 We use sifting in cooking Sifting flour What is sifting? Sifting means to put (flour, for example) through a sieve or other straining device in order to separate the fine from the coarse particles.

86 Prepared by JGL 8/9/2009 We use strainers to make fruit juice Straining juice Definition To pass through strainer to separate solids from liquids.

87 Prepared by JGL 8/9/2009 All these are methods of filtration Sifting Sieving Straining Filtration: The process by which a substance is passed through a Syllabus requirement met: Identify sieving , sifting and filtering medium in order to straining as everyday methods of separate larger particles from filtration smaller particles

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Mixtures And Their Separations

by Janadi Gonzalez-Lord on Aug 09, 2009

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Mixtures And Their Separations — Presentation Transcript