Chapter 4 science (Seperation techniques)

• What is osmosis?

  It is the movement of water from a region with a higher water concentration to a region with a lower water concentration until evenly distributed
• Acronym for DEAF + C?

  D: Distillation

  E : Evaporation

  A: Magnetic Attraction

  F: Filtration

  +

  C: Chromotagraphy
• What is a pure substance?


  A pure substance is made up of one single element/compound. It is not mixed with any other substance.
• Mixtures 


  A mixture contains 2 or more substances that are not chemically combined together.
• Filtration

  Process to separate particles of different sizes.
• Examples of mixtures:

  Sand and water

  Chalk powder and water (Suspension)

  Clay and water
• Evaporation to Dryness (Separating Solute from Solution)

  Process of obtaining a soluble solid from a solution by heating the solution until all the water has boiled off.

  Example: sodium chloride + water
• Process of evaporation

  Example: Seperating SALT from WATER

  The water in the solution will be heated until all of it has boiled off, being lost into the atmosphere. The salt solution (soluble solid) remains as residue in the evaporating dish.
• Evaporation to Dryness (Separating Solid from Liquid)

  Substances that decompose on heating cannot be obtained by evaporation to dryness
• Examples of solvent 


  Water

  Ethanol
• Distillation


  To separate a pure solvent (liquid) from a solution.
• Distillation set-up

  Boiling chips: Placed in the flask to ensure smooth boiling

  Thermometer: Measure the temperature of the inside of the flask. This ensures that the thermometer measures the boiling point of the substance that is being distillated.

  (Thermometer bulb should be beside the side arm leading to the condenser)

  Condenser: Water enters it from the bottom and leaves it from the top. The condenser should slope downwards to ensure that the pure solvent formed runs downwards into the receiver.
• Process of distillation

  1.Boiling chips will be added into the flask to ensure smooth boiling. The water even the flask evaporates and rises, entering the condenser.

  2.Water boils and become vapour. The thermometer measures the temperature of the vapour.

  3.Water vapour is cooled and condenses into pure liquid (distillate)

  4.Salt will be collected as residue.

  5.Pure water is collected as distillate.
• Chromatography

  Method of separating 2 or more components that dissolve in the same solvent.
• Examples of chromotagraphy

  Pigments in plants

  Dyes in plants

  Colouring in food
• Magnetic Seperation

  To separate non-magnetic substances from magnetic-substances
• Why is water important to us?

  1.It is essential to life

  -Living things need water to survive.

  2. It is used in industries

  -Transport products

  3. Used in homes

  -For cooking, washing and cleaning

  4. Used in activities

  -Swimming and canoeing
• 4 sources of water in SG (The 4 National Taps)


  1.Water from LOCAL CATCHMENT

  2.IMPORTED Water

  3.NEWater

  4.Desalinated water
• Water from Local Catchment + Imported water


  -Rainwater collected from drains, canals and rivers > Channeled to 17 reservoirs for storage.

  -Imports water from Johor Malaysia.

  These allow us to have water supply from the local catchment.
• NEWater


  -Ultra-clean, high-grade recycled water.

  -Obtained from treated used water in NEWater plants using 3 step process.

  1.Microfiltration

  2.Reverse osmosis

  3.Ultraviolet disinfection
• Desalinated Water


  -Pure drinking water from sea water that went through a process called Desalination [Can be carried out in Distillation/Reverse osmosis]