c10 - chemical analysis

• What effect do impurities have on boiling points?

  Increase the boiling point
• What are formulations in chemistry?

  Mixtures prepared using specific formulas
• What is the purpose of a formulation?

  To contain precise amounts of components
• What is an important feature of formulations?

  Components are always present in the same proportions
• What might different components in a formulation contribute?

  Different properties to the mixture
• What happens after testing different combinations in formulations?

  You find a successful formulation to repeat
• What is meant by a formulation in chemistry?

  A complex mixture designed as a useful product
• What can a pure substance be?

  A single element or a single compound
• What is the key characteristic of a pure substance?

  It is not mixed with any other substance
• How does a pure substance behave when heated?

  It melts and boils at fixed temperatures
• What does a fixed melting point indicate about a substance?

  It indicates the substance is pure
• How does the graph of a pure substance differ from that of an impure substance?

  A pure substance has fixed melting and boiling points
• What does a range of melting and boiling temperatures indicate?

  The substance is not pure
• What happens to the temperature of a mixture of water and an impurity when heated?

  It melts and boils over a range of temperatures
• How can you determine if a substance is pure using melting and boiling points?

  By measuring if they are fixed temperatures
• What technique is used to identify substances in a mixture?

  Paper chromatography
• What are the four ways scientists use to separate mixtures?

  • Filtration
  • Crystallization
  • Distillation (simple and fractional)
  • Chromatography
• What does paper chromatography separate substances based on?

  Different solubilities
• How do you start a paper chromatography experiment?


  Draw a pencil line near the bottom
• What is the purpose of the solvent in paper chromatography?

  To dissolve substances
• What do we call the paper in chromatography?

  The stationary phase
• What do we call the solvent in chromatography?

  The mobile phase
• What does a single spot on chromatography paper indicate?

  The substance is a pure compound
• What happens to a more soluble substance in chromatography?

  It travels further up the paper
• Why do we draw the starting line in pencil?

  To prevent it from moving with the solvent
• How do you identify an unknown substance using chromatography?

  Measure the distance moved by the substance
• What is the RF value in chromatography?

  The ratio of distance moved by substance to solvent
• What should you do if multiple substances have the same RF value?

  Repeat the experiment with a different solvent
• What happens if a substance has never been analyzed before?

  There will be no RF value in the database
• What are the key facts about pure compounds and mixtures in chromatography?

  • Pure compounds produce a single spot in all solvents.
  • Mixtures may separate into different spots depending on the solvent.
• What are the steps in a paper chromatography experiment?

  1. Draw a pencil line on chromatography paper.
  2. Place dots of colors on the line.
  3. Immerse the paper in a solvent.
  4. Measure distances moved by the substance and solvent.
  5. Calculate the RF value.
  6. Compare RF value to a database.
• What are the tests for the four gases: hydrogen, oxygen, carbon dioxide, and chlorine?

  • Hydrogen: Burning splint produces a pop sound
  • Oxygen: Glowing splint ignites
  • Carbon Dioxide: Lime water turns cloudy
  • Chlorine: Damp litmus paper turns white