Science Focus Topic 3 Notes: Separating Earth's Mixtures | Print |

Separating Earth'’s Mixtures ( pgs. 27-38 )
The Earth is rich in natural mixtures

Separating Mixtures
- when fluids are used to make solids flow, the solids must later be recovered
- separation methods are designed to take advantage of the unique properties of the substances that have been mixed

Desalinating Water
- the ‘'desert tent’ method' (much like distillation) is inexpensive, but slow, and only practical in areas which receive a lot of bright sunlight


- desalination plants, along the Red Sea, use lots of energy and are very expensive to operate
- the process of removing water from a solution is called dehydration - the solvent (which is the water, in most cases) is separated from the solution by means of evaporation

- distillation is a separation method that allows all the liquid fractions of a mixture to be separated from each other and collected independently


- all seawater contains salt, but in varying amounts - from place to place, with the dead sea having the highest concentration

Processing Petroleum
- petroleum is a natural mixture of hydrocarbons and must be processed to recover useful petroleum products
- the process that does this is called fractional distillation
- when the petroleum is heated, it changes into a gas (vaporize), which is collected and cooled, enabling it to change back into a liquid (recondense)
- the recondensed liquid is further separated (the parts redondense at different temperatures) into each of the fractional parts, that are soluble in each other, but not in water
- fractional distillation is done in a two-tower structure and the fractional products can then be converted (further processed) into over 500,000 types of petrochemicals

Solid Mixtures From Underground
- an ore is a mineral (or group of minerals) that contains a valuable substance (like gold)
- to extract the substance (gold) that needs to be recovered it must be mined and crushed, then mixed with water to create a fine suspension
- chemicals are then added to dissolve only the substance (gold) you want - the substance (gold) is then released from the solution when another substance (zinc) is added, allowing the residue (gold) to sink and be collected

- Convenience foods are often dehydrated, so they can be stored for long periods of time without spoiling (you just add water when you want to use it)
- petrochemical products include aspirin, sports equipment, eyeglasses, chewing gum, duct tape and fertilizer
- there are many different types of salt, the most common one is sodium chloride (table salt) , potassium chloride is potash
- sugar beets and sugar cane are refined to give us sugar crystals, maple sap is boiled to make ‘'sweetwater’' or maple syrup

WRAP-UP p. 39 (A good review of Topics 1-3)