1.8-1.13 IGCSE Chemistry 2018

1 Principles of chemistry 

2 Inorganic chemistry 

3 Physical chemistry 

4 Organic chemistry 

1 Principles of chemistry 

(b) Elements, compounds and mixtures 
Students should:
1.8 understand how to classify a substance as an element, compound or mixture 1.9 understand that a pure substance has a fixed melting and boiling point, but that a mixture may melt or boil over a range of temperatures 1.10 describe these experimental techniques for the separation of mixtures: • simple distillation • fractional distillation • filtration • crystallisation • paper chromatography. 1.11 understand how a chromatogram provides information about the composition of a mixture 1.12 understand how to use the calculation of Rf values to identify the components of a mixture 1.13 practical: investigate paper chromatography using inks/food colourings

Notes:
https://pmt.physicsandmathstutor.com/download/Chemistry/GCSE/Notes/Edexcel-IGCSE/1-Principles-of-Chemistry/Set-A/b)%20Elements%20compounds%20and%20mixtures.pdf

• Elements, Compounds, Mixtures 1 MS
• Elements, Compounds, Mixtures 1 QP

• 1.8: Understand How to Classify a Substance as an Element, Compound or Mixture

  
  

  CLASSIFICATIONS:

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  CLASS	DEFINITION
  ELEMENT	A Substance Made Up of Atoms that all Contain the Same Number of Protons (One Type of Atom) and Cannot be Split into Anything Simpler Example: Hydrogen, Oxygen, Carbon
  COMPOUND	A Substance Made Up of Two or More Elements Chemically Combined Together Example: Copper (II) Sulphate, Calcium Carbonate
  MIXTURE	A Combination of Two or More Substances (Elements and / or Compounds) that are Not Chemically Joined Together Example: Sand and Water, Oil and Water

  
  

  
  

  Example:

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• 1.9: Understand that a Pure Substance has a Fixed Melting and Boiling Point, but that a Mixture may Melt or Boil Over a Range of Temperatures

  
  

  PURE SUBSTANCE: Contains Only One Substance, with No Other Substances Mixed Together

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  • Has Fixed Melting and Boiling Point as they Consist of Only One Substance so All Molecules will have the Same Melting and Boiling Points

  
  

  MIXTURE: A Combination of Two or More Substances (Elements and / or Compounds) that are Not Chemically Joined Together

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  • Has a Range of Melting and Boiling Point as they Consist of Different Substances that Melt or Boil at Different Temperatures

  
  
  
  

  1.10: Describe these Experimental Techniques for the Separation of Mixtures: Simple Distillation, Fractional Distillation, Filtration, Crystallization, Paper Chromatography

  
  

  SIMPLE DISTILLATION

  Diagram Showing the Simple Distillation of a Mixture of Salt and Water

  USE: To Separate a Liquid from a Solution (E.g Water from a Solution of Salt Water)

  EXPLANATION: Solution is Heated and Water Vapours will Rise and Evaporate Water Vapours will Pass through the Condenser, where it Cools and Condenses, turning into a Liquid that will be Collected in a Beaker After All the Water is Evaporated from the Solution, the Solute will be Left Behind

  
  
  
  
  

  FRACTIONAL DISTILLATION

  Diagram Showing the Fractional Distillation of a Mixture of Ethanol and Water

  USE: To Separate Two or More Liquids that are Miscible with One Another (E.g Ethanol and Water from a Mixture of the Two)

  EXPLANATION: Solution is Heated at Temperature of Substance with the Lowest Boiling Point This Substance will Rise and Evaporate, and Vapours will Pass through a Condenser, where it Cools and Condenses, turning into a Liquid that will be Collected in a Beaker All of this Substance is Evaporated and Collected, Leaving Behind a Mixture or a Substance

  
  
  
  
  

  FILTRATION

  Diagram Showing the Filtration of a Mixture of Sand and Water

  USE: To Separate an Undissolved Solid from a Mixture of the Solid and a Liquid / Solution ( E.g Sand from a mixture of Sand and Water)

  EXPLANATION: Filter Paper is Placed in a Filter Funnel Above Another Beaker Mixture of Insoluble Solid and Liquid is Poured into the Filter Funnel Filter Paper will Only Allow Small Liquid Particles to Pass Through as the Filtrate Solid Particles are Too Large to Pass Through the Filter Paper so will Stay Behind as a Residue

  
  
  
  
  

  CRYSTALLIZATION

  Diagram Showing the Process of Crystallization

  USE: To Separate a Dissolved Solid from a Solution, When the Solid is Much More Soluble in Hot Solvent than in Cold (E.g Copper (II) Sulphate from a Solution of Copper (II) Sulphate in Water)

  EXPLANATION: Solution is Heated, Allowing the Solvent to Evaporate to Leave a Saturated Solution Saturated Solution is Allowed to Cool and Solids will Come Out of the Solution and Crystals will Grow Crystals are Collected and Allowed to Dry

  
  
  
  
  

  PAPER CHROMATOGRAPHY

  Diagram Showing the Paper Chromatography of Ink and Plant Dye

  USE: To Separate Substances that have Different Solubilities in a Given Solvent (E.g Different Coloured Inks that have been Mixed to Make Black Ink)

  EXPLANATION: Pencil Line is Drawn on Chromatography Paper and Spots of Ink / Dye is Placed on it Paper is Lowered into a Bucket of Solvent, Allowing the Solvent to Travel Up the Paper, Taking some of the Coloured Substances with it Different Substances will have Different Solubilities so will Travel at Different Rates, Causing the Substances to Spread Apart This will show the Different Components of the Ink / Dye
  
  

  1.11: Understand How a Chromatogram Provides Information about the Composition of a Mixture

  
  

  PAPER CHROMATOGRAPHY - COMPOSITION OF A MIXTURE

  Diagram Showing the Composition of an Ink using Paper Chromatography

  COMPOSITION OF A MIXTURE: Chromatograms will Show the Composition of a Mixture as the Different Coloured Substances (Components) will Spread Apart as they will Have Different Solubilities so will Travel at Different Rates A Pure Substance will Only Produce One Spot on the Chromatogram during Paper Chromatography In the Diagram Above, Red, Blue and Yellow are Three Pure Substances, whilst the Sample on the Left is a Mixture of All Three
  
  

  1.12: Understand How to Use the Calculation of Rf Values to Identify the Components of a Mixture

  
  

  Rf VALUES: Used to Identify the Components of Mixtures

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  • The Rf Value of a Particular Compound is Always the Same
  • This Allows Industries to Use Chromatography to Identify Compounds in Mixtures

  
  
  

  EQUATION:

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  Rf Value =     Distance Moved by Compound    ÷     Distance Moved by Solvent
  
  

  1.13: Practical: Investigate Paper Chromatography using Inks / Food Colourings

  
  

  PAPER CHROMATOGRAPHY

  Diagram Showing the Paper Chromatography of Ink and Plant Dye

  USE: To Separate Substances that have Different Solubilities in a Given Solvent (E.g Different Coloured Inks that have been Mixed to Make Black Ink)

  METHOD: Pencil Line is Drawn on Chromatography Paper and Spots of Ink / Dye is Placed on it Paper is Lowered into a Bucket of Solvent, Allowing the Solvent to Travel Up the Paper, Taking some of the Coloured Substances with it Allow Chromatography to Occur until the Solvent Reaches the Top of the Paper

  RESUTS: As the Solvent Travels Up the Paper, Different Substances will have Different Solubilities so will Travel at Different Rates, Causing the Substances to Spread Apart This will show the Different Components of the Ink / Dye