Experimental chemistry

• Pipette


  Apparatus used to measure and transfer small volumes of liquids accurately

  
• Burette


  Apparatus used to measure and deliver variable volumes of liquids accurately
• Collection of Gas


  1. Upward delivery

  2. Downward delivery

  3. Displacement of water
• Method of Collection


  • For gases that are soluble in water and less dense than air
  • For gases that are soluble in water and denser than air
  • For gases that are insoluble or slightly soluble in water
• Measurement


  • Quantity
  • SI unit
  • Other units
  • Apparatus
• Time is measured in seconds (s), minutes (min) or hours (h) using a stopwatch or stopclock
• Temperature is measured in kelvin (K) or degree Celsius (°C) using a thermometer or temperature sensor with datalogger
• Mass is measured in kilograms (kg), grams (g) or tonnes (ton) using a beam balance and electronic balance
• Length is measured in metre (m), cm, mm or dm using a metre rule and measuring tape
• Volume of gas is measured in cubic metre (m3), cm3 or dm3 using a Gas syringe
• Volume of liquids is measured in cubic metre (m3), cm3 or dm3 using various apparatus
• Accuracy


  • Estimate, Rough
  • 0.5 cm3
  • 0.1 cm3
  • 0.05 cm3
• Purification


  • Test for Purity
  • Effects of impurities
  • Separation Techniques
• Test for purity: fixed melting point and boiling point, only one spot on the chromatogram
• Effects of impurities: lower melting point, higher boiling point, melts and boils over a range of temperatures
• Separation Techniques


  • Using Magnetic Attraction
  • Sieving
  • Using Suitable Solvents
  • Filtration
  • Evaporation to Dryness
  • Crystallisation
  • Simple Distillation
  • Fractional distillation
  • Paper Chromatography

  
• Mixture


  Two or more substances that are not chemically combined together
• Separating Solid-Solid Mixtures


  1. Using Magnetic Attraction

  2. Sieving

  3. Using a Suitable Solvent
• Separating Solid-Solid Mixtures


  • Iron fillings and sulfur powder
  • Calcium carbonate (powder) and sugar (crystals)
  • Sand and salt, solvent: water
• Separating Solid-Liquid Mixtures


  1. Filtration

  2. Evaporation to Dryness

  3. Crystallisation
• Separating Solid-Liquid Mixtures


  • Purification of drinking water
  • Obtaining salt from seawater
  • Obtaining sodium and potassium salts
• Separating Liquid-Liquid Mixtures


  1. Simple Distillation

  2. Fractional Distillation

  
• Separating Liquid-Liquid Mixtures


  • Obtain distilled water from impure salt water
  • Obtain pure water from ink
  • Fragrance oil in perfume industry
  • Separating ethanol and water

  
• Paper Chromatography


  1. Starting line is drawn with pencil

  2. Starting line is above solvent level

  3. Spots of the samples on the start line must be small

  4. If spots do not travel, sample is insoluble in solvent

  5. A pure substance will produce only one spot on the chromatogram

  
• Paper Chromatography


  • To separate components like DNA fragments
  • To separate dyes in ink and pigments
  • To identify banned substances in food and drugs
  • To identify if a substance is pure