Science 1A Chapter 4

• Magnetic substances


  Substances such as iron and steel are attracted to a magnet
• Non-magnetic substances


  Substances such as plastic and paper are not attracted to a magnet
• Separating magnetic and non-magnetic substances

  Use a magnet to attract the magnetic substances
• Mixture of iron filings and sulfur

  • Iron filings are attracted to the magnet, sulfur is left behind
• Sulfur is non-magnetic
• The magnet separates the magnetic iron filings from the non-magnetic sulfur
• Magnetic attraction


  Used to separate magnetic substances from non-magnetic substances
• Application of Magnetic Attraction in Singapore

  • Scrap metal
  • Aluminium
  • Copper
  • Iron
• Removing iron from scrap metal mixture

  1. Pass a strong magnet over the scrap metal

  2. Iron can then be reused or recycled
• Magnetic materials removed

  • Steel bolts and nuts
  • Iron bar
  • Steel pipe
  • Iron chain
• Non-magnetic materials left behind

  • Glass mirror
  • Plastic car parts (e.g., bumper)
  • Rubber tyre
• Sieve


  A sieve has small holes called pores, which are of a particular size
• Separating a mixture of substances with different particle sizes

  1. Particles smaller than the pores pass through the sieve

  2. Particles bigger than the pores are retained by the sieve
• Filtration

  1. Pouring a mixture onto a filter funnel lined with filter paper

  2. Water particles pass through the pores in the filter paper

  3. Larger particles are retained by the filter paper
• Filtration applications

  • Tea strainer separates tea leaves from tea
  • Coffee filter separates coffee grounds from coffee
  • Water filter removes impurities from water
• Residue


  The solid that is left on the filter paper
• Filtrate


  The liquid that passes through the filter paper
• Filtration

  • Filtration is the process of separating substances of different particle sizes using a sieve.
• Sand and rocks

  • Laid as filters during the construction of a siltation pond
• Siltation pond


  Water in a siltation pond is cleaned by filtration
• Groundwater


  Found below the surface of the ground, filtered as it flows through the holes between the sand and rocks of different sizes in a siltation pond
• Nose


  • Acts as a filter, with hairs and mucus trapping large solid particles in the air we breathe in, preventing them from entering our lungs
• Filtration can also be used to produce drinking water
• Magnetic attraction is used in waste management.
• Evaporation is used to extend the shelf life of food such as ikan Bilis and reduce food wastage.
• Chromatography is used in food testing to ensure the food does not contain harmful substances and is safe for comsumption.
• In Singapore, filtration and reverse osmosis are used in the recycling of used water to obtain portable water.
• Solute


  Solid component of a solution
• Solvent


  Liquid component of a solution
• Evaporation

  1. Solvent changes from liquid to gas at a much lower temperature than the solute

  2. Solvent is removed, leaving behind the solute as the residue
• Evaporation is a process used to obtain a dissolved solid (solute) from a liquid (solvent)
• Food preserved using evaporation

  • Herbs
  • Spices
  • Dried small fishes (e.g. ikan bilis)
• Water is essential for decomposition. In order to preserve food, water is removed using evaporation.
• Vacuum drying


  Food is dried in a vacuum oven where air is removed, allowing water to evaporate more quickly than under normal temperature and pressure
• Vacuum drying is a preferred method of food preservation as normal drying causes food to deteriorate in flavour
• Evaporation


  Used in the production of salt, where hot water is pumped deep into the ground to dissolve the salt, then the salt solution is pumped up to pans on the ground and the water is allowed to evaporate under the sun so that solid salt is left behind
• Water cycle


  1. Heating (evaporation)

  2. Cooling (condensation)