chromatography

• 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 do you place on the pencil line in paper chromatography?

  Dots of different colors
• 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 color
• What happens to a mixture of colors in chromatography?

  It separates into different spots
• What is a key fact about pure compounds in chromatography?

  They produce a single spot in all solvents
• Why do we draw the starting line in pencil?

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

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

  Distance moved by substance divided by 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 is the purpose of paper chromatography in this context?

  To identify substances in food coloring
• What is the role of the water in the chromatography process?

  It acts as the solvent
• What happens if the pencil line touches the water?

  The ink will wash off the line
• Why do we put a lid on the beaker during chromatography?

  To reduce evaporation of the solvent
• When do we remove the chromatography paper from the beaker?

  When the water has traveled 3/4 up
• What does it indicate if the unknown color separates into three spots?

  It is a mixture of three colors
• How do we determine which known colors are in the unknown sample?

  By comparing the spots' alignment
• What does the absence of color B in the unknown sample indicate?

  Color B is not present in the mixture
• What is the first step to calculate the RF value?

  Measure the distance from the pencil line
• What do RF values indicate in chromatography?

  They help identify the chemical's identity
• What should be done if multiple chemicals have the same RF value?

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

  Further analysis is needed to identify it