Chapter 2

• Instruments used to measure time:

  1. digital stopwatch
  2. analogue stopwatch
• Instruments used to measure mass:

  1. Beam balance
  2. Electronic balance
• Units used for time:

  1. Minute
  2. Second
  3. Hour
• Units used for temperature:

  1. Degrees Celsius
  2. Kelvin
• Units used for mass:

  1. Gram
  2. Kilogram
  3. Milligram
• Instruments used to measure volume:

  1. Measuring cylinder
  2. Conical flask
  3. Beaker
  4. Pipette
  5. Burette
  6. Volumetric flask
• Units used for volume:

  1. Centilitre
  2. Millilitre
  3. Litre
• Collection of a gas depends on it's physical properties such as:

  1. Solubility in water
  2. Density compared to air
• What can be used to collect gases?


  A gas jar
• What is used to measure volume of gases? 


  A gas syringe
• Methods of collecting gases

  1. Displacement of water
  2. Upward delivery
  3. Downward delivery
• What is displacement of water?


  This method is suitable to collect gases which do not dissolve in water
• Examples of gases used for displacement of water:

  1. Hydrogen
  2. Oxygen
  3. Carbon dioxide
• What is upward delivery?


  It is used to collect gases which are soluble in water and less dense than air.
• Examples of gases used for upward delivery:

  1. Ammonia
• What is downward delivery?


  It is used to collect gases which are soluble in water and denser than air
• Examples of gases used for downward delivery:

  1. Chlorine
  2. Hydrogen chloride
• How are dry gases collected?


  Dry gases are obtained by passing moist gases through a drying agent
• Examples of drying agents:

  1. Concentrated sulfuric acid
  2. Quicklime (calcium oxide)
  3. Fused calcium chloride
• How is concentrated sulfuric acid used?


  It is used to collect dry gases such as hydrogen chloride and chlorine. However, it cannot be used to dry ammonia as it reacts with sulfuric acid
• How is Quicklime used? 


  It is used to dry ammonia
• How is Fused calcium chloride used?


  It is used to dry most gases. It is calcium chloride that has been previously heated
• What is a pure substance?


  A pure substance is made up of only one substance
• Pure substances can be identified by:

  1. Determining the melting point of a solid
  2. Determining the boiling point of a liquid
  3. By chromatography
• Impurities can affect the melting point of substances by:

  1. Lowering the melting point of a substance
  2. Melting occurs over a range of temperatures
• How can boiling point of liquid be found?


  Boiling can be found by using simple distillation process
• Melting point of benzoic acid


  122 degrees celsius
• Boiling point of pure propanone


  56 degrees celsius
• Effects of impurities on boiling points

  1. Impurities increase the boiling point of a substance
  2. Impure liquids boil over a range of temperature
• Effect of pressure

  1. If pressure is increased boiling point is also increased.
  2. If pressure is decreased boiling point is also decreased
• What is chromatography?


  Chromatography is a method of seperating a mixture using a solvent
• Paper chromatography is used to seperate:

  1. Dyes in ink
  2. Pigments in plants
  3. Amino acids obtained from proteins
  4. To identify drugs or poisons (pesticides)
  5. To detect traces of banned substances
• What is Rf values?


  It is the ratio between the distance travelled by the component and the distance travelled by the solvent.
• List of chromatography

  1. To seperate the components in a sample
  2. To identify the number of components in a sample
  3. To identify the components
  4. To determine whether a sample is pure
• Separation techniques:

  1. Filtration
  2. Decontamination
  3. Sublimation
  4. Crystallisation
  5. Simple distillation
  6. Fractional distillation
  7. Evaporation to dryness
  8. Separating funnel
  9. Magnetic attraction
• Types of mixtures needed for seperation

  1. Solid and liquids
  2. Solids
  3. Liquid from a solution
  4. Liquids
• To seperate a solid (insoluble) from a liquid

  1. Decantation
  2. Flitration
• To seperate a mixture from solids (insoluble)

  1. Sublimation
  2. Magnetic attraction
• To seperate a solid from a solution

  1. Evaporation dryness
  2. Crystallisation
• What is Evaporation to dryness?


  It is a method used to obtain a solid from a solution. During the process the mixture is heated strongly in a crucible till the liquid has evaporated. After Evaporation, the solid obtained is in the form of a powder