Thursday 4th September
TODAY WE ARE
LEARNING ABOUT
 How can we use paper chromatography to identify an unknown mixture?
TODAY'S
KEY WORDS ARE
  • Chr_m_t_gr_phy
  • M_b_l_  ph_s_
  • St_t__n_ry  ph_s_
  • Rf  V_l__
  • _nstr_m_nt_l  m_th_d
    		•

    Memory Anchor:

    YOU WILL SHOW
    YOUR LEARNING BY...

    • Super Challenge:

      Stretch:

      Challenge:

    Key Questions:

    1. What can Chromatography be used to separate?
      • Chromatography can be used to separate mixtures such as inks and can give information to help identify the substances from which it is made.
    2. What are the names of the two phases involved in chromatography?
      • Stationary phase and mobile phase.
    3. What does seperation depend on?
      • Separation depends on the distribution of substances between the phases.
    4. How should the Rf value be expressed?
      • The ratio of the distance moved by a compound (centre of spot from origin) to the distance moved by the solvent
    5. How is the Rf value calculated?
      • Rf = distance moved by substance / distance moved by solvent
    6. How do the Rf values of compounds change in different solvents?
      • Different compounds have different R values in different solvents.
    7. How can compounds be identified?
      • Rf values can be used to help identify the compounds.
    8. How many spots are produced by a pure compound compared to a compound in a mixture?
      • The compounds in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents.
    9. How can paper chromatography be used to separate mixtures?
      • A spot of each mixture is dropped onto the start line of the paper chromotography. The paper chromatogram is introduced to a solvent and left for seperation to take place.
    10. How can chromatographic methods can be used for distinguishing pure substances from impure substances?
      • The compounds in a mixture may separate into multiple spots depending on the solvent, but a pure substance will always produce a single spot in all solvents.
    11. How can chromatograms be used to determine R values?
      • The R value can be calculated and compared. RT = distance moved by substance / distance moved by solvent
    12. How can elements and compounds be detected?
      • Elements and compounds can be detected and identified using instrumental methods. Instrumental methods are accurate, sensitive and rapid.
    13. What are the advantages of instrumental methods compared with the chemical tests?