Experimental chemistry

• Physical property


  Density
• Atom


  Gains or loses electrons. The number of protons and neutrons remains the same
• Cations


  Atoms that lose electrons to form positively charged ions
• Ca2+


  Calcium ion with a charge of 2+
• Number of neutrons in Ca atom is 20
• Number of protons in Ca atom is 20
• Number of electrons in Ca atom is 20
• Ca atom loses 2 electrons to form Ca2+ ion. Thus, it has 20-2=18 electrons
• Anions


  Atoms of non-metals that gain electrons to form negatively charged ions
• F


  Fluorine atom
• Number of electrons in F atom is 9
• Number of protons in F atom is 9
• Number of neutrons in F atom is 10
• 1. 
     

  Fluoride ion
• F atom gains 1 electron to form F- ion. Thus, it has 9+1=10 electrons
• Measurement


  • Time
  • Temperature
  • Mass
  • Length
  • Volume of gas
  • Volume of liquids
• SI unit


  seconds (s)<|>kelvin (K)<|>kilograms (kg)<|>metre (m)<|>cubic metre (m³)<|>cubic metre (m³)
• Other units


  • minutes (min) or hours (h)
  • degree Celsius (°C)
  • grams (g) or tonnes
  • millimetre (mm) or centimetre (cm)
  • cubic centimetre (cm³) or cubic decimetre (dm³)
  • cubic centimetre (cm³) or cubic decimetre (dm³)
• Apparatus


  • digital stopwatch
  • thermometer or temperature sensor with datalogger
  • beam balance and electronic balance
  • metre rule and measuring tape
  • gas syringe
• Name of apparatus


  • Beaker, conical flask
  • Measuring cylinder
  • Burette
  • Pipette
• Collection of Gas


  • Upward delivery
  • Downward delivery
  • Displacement of water
• Type of Gas


  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
• Gas produced during a reaction between an acid and a metal/metal carbonate
• 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-Liquid Mixtures


  • Filtration
  • Evaporation to Dryness
  • Crystallisation
• Separating Liquid-Liquid Mixtures


  • Simple Distillation
  • Fractional Distillation
• Separating Solid-Solid Mixtures


  • Using Magnetic Attraction
  • Sieving
  • Using a Suitable Solvent
• Simple Distillation


  To obtain the liquid. Process involved: boiling and condensation.
• Fractional Distillation


  To obtain liquids from miscible mixtures. Fractionating column which is packed with glass beads to provide a larger surface area for vapour to condense on.
• Evaporation to Dryness


  To obtain the soluble solid. Substance with a lower boiling point will boil and vapourise.
• Crystallisation


  To obtain the soluble solid. For substances that will burn and break down into simple substances when heated.
• Paper Chromatography


  Separating two or more components which have different solubilities in the same solvent.
• A pure substance will produce only one spot on the chromatogram