2 Chapter 3: Separating Technqiues 3.1 ChromatographyChromatography is a technique of using a solvent to separate a mixture into its componentsExample: Paper ChromatographyPaper chromatography can be use to separate dyes in ink, amino acids obtain from proteins, identify toxics
3 How does chromatography works? Chapter 3: Separating TechnqiuesHow does chromatography works?A spot of food colouring is applied to chromatography paperOnce the paper is dipped in ethanol, it soaks up.Ethanol travel up the paper, carrying dyes alongDye that is not very soluble > carried not farDye that is soluble > Carried far
4 How can we identify a banned substance present in food colouring? Chapter 3: Separating TechnqiuesHow can we identify a banned substance present in food colouring?Chromatography was performed on a sample of food colouring (‘X’) and 4 banned dyes (‘A’, ‘B’, ‘C’, ‘D’)If X contains any of the 4 banned dyes, itt is not safe to be consumed.
5 Interpreting Chromatography Chapter 3: Separating TechnqiuesInterpreting ChromatographyChromatography paper with separated component is known as chromatogramSolvent frontThe chromatogram shows the food colouring used in the experiment was a mixture of two dyes.Coloured spots
6 Interpreting Chromatography Chapter 3: Separating TechnqiuesInterpreting ChromatographyChromatography paper with separated component is known as chromatogramSolvent frontThe chromatogram has only a spot, this dye is made up of a dye. Thus, it’s pure.
7 What conclusion can be drawn from this chromatogram? Chapter 3: Separating TechnqiuesWhat conclusion can be drawn from this chromatogram?XABCDIdentical dyes produce spots at same heightSample X does not contains the banned dyes A,B,DHowever, X contains the banned dye. Therefore, it must not be consumed
8 What conclusion can be drawn from this chromatogram? Chapter 3: Separating TechnqiuesWhat conclusion can be drawn from this chromatogram?XABCDDyes A&D are pureBoth dye B & C are mixture of 2 different dyesSample X is a mixture of 3 dyes
9 How do we identify colourless substances? Chapter 3: Separating TechnqiuesHow do we identify colourless substances?Chromatography can also be used for colourless substances such as amino acids. To separate and analyse colourless substance, we apply a locating agent on a chromatogram.If no dye appear after using locating agent, this means that solvent can’t dissolve the dye
10 Uses of Chromatography Chapter 3: Separating TechnqiuesUses of ChromatographySeparate the components in a sampleIdentify number of components in a sampleIdentify the components present in a sampleDetermine whether if a sample is pure
11 Chapter 3: Separating Technqiues Take Note:Pencil lineWhy do we use pencil?Pencil is insoluble in solventSolvent used cannot above the pencil line.
12 Separation Techniques Chapter 3: Separating TechnqiuesSeparation TechniquesBesides chromatography, there are other techniques to separate mixtures.A solid from liquid – sand + water : FiltrationSolids – Sand + Iron Fillings : Magnetic AttractionLiquids – Fractional DistillationA liquid form a solution – Distillation
13 Separating insoluble solid from liquid - Filtration Chapter 3: Separating TechnqiuesSeparating insoluble solid from liquid - FiltrationWe can use filtration to separate solid particles from a liquid (often it is water)Example of Small Solid particles includes sand, clay, dust particles and precipitatesResidueFilter PaperFiltrate
14 Separating insoluble solid from liquid – Evaporation to Dryness Chapter 3: Separating TechnqiuesSeparating insoluble solid from liquid – Evaporation to DrynessTo recover salt from salt solution, we evaporate the solution to drynessSalt SolutionEvaporating Dish
15 Separating insoluble solid from liquid – Crystallisation Chapter 3: Separating TechnqiuesSeparating insoluble solid from liquid – CrystallisationWhen a substance decomposes on heating or can lose its water of crystallisation, we do not evaporate it to dryness, we crystallise it.Sugar Decomposes on heating
16 How do we purify by crystallisation? Chapter 3: Separating TechnqiuesHow do we purify by crystallisation?In crystallisation, water is removed by heating the solution. Heating is stopped at the stage when a hot saturated solution is form. If the resulting solution is allowed to cool to room temperature, the dissolved solid will be formed as pure crystals.
17 How do we test for a saturated solution? Chapter 3: Separating TechnqiuesHow do we test for a saturated solution?A clean glass rod can be used to test whether a solution is saturated.It is dipped into the solution and removed. There will be a small amount of solution on the rodIf small crystals form on the rod as the solution cools, the solution is saturatedWe say the solution is at is saturated point or crystallisation pointSaturated points = maximum amount of solute in solvent at certain room temperature.
18 Separating Solids (E.g.: Salt and Sand) Chapter 3: Separating TechnqiuesSeparating Solids (E.g.: Salt and Sand)Methods: By adding a suitable solvent and filtrationPour some distilled water (dissolve the salt) into mixture of common salt and sand. Stir and warm (to speed up whole dissolving processes)Filter the mixtureSand (Residue)Salt (dissolved) + Water [Filtrate]
19 Separating Solids (E.g.: Salt and Sand) Chapter 3: Separating TechnqiuesSeparating Solids (E.g.: Salt and Sand)Methods: By adding a suitable solvent and filtration3. Wash the residue (remove salt solution, get rid of salt) with a little distilled water to remove all salt solution from it. Residue = Sand4. Evaporate the filtrate to dryness. Salt is recoveredSand (Residue)Salt (dissolved) + Water [Filtrate]Note: If is sugar, continue up till step 3. As for step 4, it will be crystallisation.
20 Separating a Liquid from a solution Chapter 3: Separating TechnqiuesSeparating a Liquid from a solutionWhen a solid dissolves in a solvent, a solution is formed (i.e.: Salt solution)A pure solvent can be separated from a solution by simple distillationDistillation is the process of boiling liquid and condensing vapour.For example, pure water can be obtained from salt solution by this processTo collect solute from solvent, we evaporate solvent.
21 How does simple distillation work? Chapter 3: Separating TechnqiuesHow does simple distillation work?In the distillation flask, water boils and enter condenserIn the condenser, water vapour condenses.Pure water is collected as the distillateBoiling chips in the flask is used to smoothen boiling.213
22 Things to take note when doing.. Chapter 3: Separating TechnqiuesThings to take note when doing..Thermometer: Should be placed beside the side arm of distillation flask. (Temperature of thermometer = Boiling point of solvent)Condenser: Consists of 2 tubes : Inner tube and outer wet jacket. Cold running water enters from bottom of condenser and leaves from top.If the distillate is volatile, the receiver can be put in a large container filled with ice which helps keep temperature of distillate so that it remains in liquid state.
23 Separating Miscible Liquids – Fractional Distillation Chapter 3: Separating TechnqiuesSeparating Miscible Liquids – Fractional DistillationUnlike oil and water, ethanol and water mix together completely to form a solution. They are said to be miscibleIf two liquids are miscible, they must be separated by fractional distillation.
24 Separating Miscible Liquids – Fractional Distillation Chapter 3: Separating TechnqiuesA fractionating column, is attached to the round-bottomed flash and the condenser for fractional distillation. Many glass beads in the fractionating column provide a large surface area for vapour to condense on. Other than glass beads, a fractionating column may be filled with plates or a spiral
25 Example of mixture of 2 liquids Chapter 3: Separating TechnqiuesExample of mixture of 2 liquidsEthanol and water are soluble in each otherTo separate these 2 miscible liquid, we use fractional distillationThe boiling point of ethanol is 78 ℃while the boiling point of water is 100 ℃In fractional distillation, liquid with lower boiling point(ethanol) will be collected first
26 Chapter 3: Separating Technqiues How does fractional distillation work?In the distillation flask, the ethanol and water boils and liquids may distil togetherVapours of liquids with higher boiling points condense along fractionating column and re-enter the round-bottomed flaskEthanol distils over. In condenser, ethanol vapour condenses.Ethanol is collect as distillate.2314
27 Chapter 3: Separating Technqiues How does temperature change as solution of ethanol and water undergoes fractional distillation?Temperature (℃)The temperature of mixture increases as it’s heatedAt 78 ℃, ethanol distils over. The temperature remains constant until all ethanol has distilled out of round-bottomed flaskTemperature then increased until 100 ℃. At 100 ℃, water distils over. Temperature remains unchanged as water is being distilled.
28 Industrial applications of fractional distillation Chapter 3: Separating TechnqiuesIndustrial applications of fractional distillationFractional distillation is used in industries to obtain nitrogen, argon, oxygen from airFractional distillation can be used to separate mixtures of liquids such as crude oilEthanol is formed when glucose solution undergoes fermentation in presence of yeast.We can separate ethanol from glucose solution by fractional distillation