Separation Techniques

• What techniques can separate solids from liquids?

  Filtration, evaporation, and crystallization
• What is a mixture of a liquid and an insoluble solid called?

  A mixture
• What do we call a liquid with a soluble solid dissolved in it?

  A solution
• In a solution, what is sodium chloride referred to as?

  Solute
• What is the role of water in a solution of sodium chloride?

  Solvent
• How does filtration work in separating solids from liquids?

  It uses filter paper to trap solids
• What is the purpose of filter paper in filtration?

  To allow liquids to pass through
• What happens when a soluble solid is dissolved in a liquid?

  It forms a solution
• What are the two options for separating a soluble solid from a liquid?

  Evaporation or crystallization
• What equipment is used for evaporation in separating solids?

  Evaporating dish or crucible
• What is the effect of heating a solution in evaporation?

  It causes the solvent to evaporate
• What is the benefit of evaporation in separating solids?

  It's quick and easy
• What is thermal decomposition?

  Breaking down solids when heated
• What technique is used for solids that decompose when heated?

  Crystallization
• What is the first step in crystallization?

  Heat the solution gently
• Why do crystals form when cooling a solution?

  Solids are less soluble at colder temperatures
• What is the last step after filtering crystals from a solution?

  Dry the crystals
• What are the steps involved in crystallization?

  1. Heat the solution gently.
  2. Allow some solvent to evaporate.
  3. Stop heating when crystals form.
  4. Filter out the crystals.
  5. Dry the crystals.
• Compare evaporation and crystallization for separating solids.

  • Evaporation:
  • Quick and easy
  • Risk of thermal decomposition
  • Crystallization:
  • Slower process
  • Preserves solid integrity
• What is the purpose of chromatography?

  To separate substances in a mixture
• What is the first step in paper chromatography?

  Draw a baseline with a pencil
• What do we call the line drawn on the filter paper?

  Baseline
• What should be done after drawing the baseline?

  Add the sample of ink
• What type of solvent can be used in paper chromatography?

  Water or ethanol
• Why is it important not to submerge the pencil line in solvent?

  To prevent ink from dissolving prematurely
• What is a chromatogram?

  The pattern of spots left after chromatography
• What are the mobile and stationary phases in chromatography?

  Mobile phase is the solvent; stationary phase is the paper
• How do different chemicals move in chromatography?

  They change between mobile and stationary phases
• What determines how fast a chemical moves up the paper?

  Solubility in the solvent and attraction to paper
• What is the formula for calculating the rf value?

  rf = distance travelled by substance / distance travelled by solvent
• If a pink substance travels 6 cm and the solvent travels 10 cm, what is the rf value?

  $0.6$
• What happens when chromatography is performed with a pure substance?

  It produces a single spot on the chromatogram
• How can changing the solvent or paper affect chromatography results?

  It can change the chromatogram and rf values
• Why must chemists consider the solvent and paper type when looking up rf values?

  Because they affect the chromatography results
• What are the two types of distillation mentioned?

  Simple distillation and fractional distillation
• What is the purpose of simple distillation?

  To separate a liquid from a solution
• How can simple distillation be used with seawater?

  To separate pure water from seawater
• What equipment is used in simple distillation?

  A flask, thermometer, condenser, and heating device
• What is the function of the bung in the flask?

  To seal the flask and prevent gas escape
• Why is a thermometer used in the distillation process?

  To measure the temperature inside the flask