chem earths resources

• Polymers are formed by joining together a large number of monomers
• The properties of polymers depend on both the monomer and the conditions used to make the polymer
• Low-density polyethylene is a soft polymer, while high-density polyethylene is harder, both made from the same monomer but under different conditions
• To change the properties of a polymer, one can alter the reaction temperature, pressure, or catalyst
• Thermal softening polymers melt when heated, allowing for reshaping when soft and solidifying upon cooling
• Thermosetting polymers do not melt when heated because their polymer chains are connected by strong cross-links that are not broken by heat
• Potable water is safe to drink, while pure water contains no dissolved solids such as salts and has a pH of 7
• To analyze the purity of a water sample:

  • Check the pH using universal indicator paper; pH of 7 indicates pure water
  • Test for dissolved solids by evaporating the water in an evaporating Basin and weighing it before and after; an increase in mass indicates dissolved solids
• Pure water may still contain dissolved gases, which are not investigated in this practical
• To purify water by distillation:

  • Use a conical flask with a water sample heated gently to form steam
  • The steam travels through a delivery tube into a test tube placed in a beaker with ice and water
  • The steam condenses back into liquid water in the test tube, producing distilled water which is pure with no dissolved solids and a pH of 7
• Corrosion is the destruction of materials by chemical reactions with substances in the environment
• Rusting only applies to iron and alloys of iron like steel; for other metals, use the term corroding
• To test the conditions required for rusting:

  • Test tube 1: iron nail in distilled water open to air
  • Test tube 2: iron nail in distilled water, boiled and covered with oil
  • Test tube 3: anhydrous calcium chloride powder to remove water, with a rubber bung to prevent moist air from entering
• Rusting requires both air and water, as seen by rust forming in test tube 1 but not in test tubes 2 & 3
• To prevent corrosion, use barriers like grease, paint, or electroplating with a metal like aluminium
• Galvanizing involves coating iron with zinc, acting as a barrier against air and water; if the zinc gets scratched, it still prevents corrosion because zinc is more reactive than iron, corroding instead
• Sacrificial protection involves using a more reactive metal like zinc to protect a less reactive metal like iron; zinc corrodes instead of iron, as seen in galvanized nails and zinc bars on a ship's hull
• An alloy contains a metal blended with other elements, making it a mixture
• Alloys tend to be harder than pure metals because the atoms in alloys are different sizes, disrupting the layers and preventing them from sliding
• Bronze is an alloy of copper and tin, used for statues due to its hardness and resistance to corrosion
• Brass is an alloy of copper and zinc, used for musical instruments and door handles
• Gold is alloyed with silver, copper, and zinc to make it harder for jewelry; purity of gold is rated in carats, with 24 karat being 100% pure gold
• Steel is an alloy of iron containing specific amounts of carbon; high carbon steel is extremely hard but brittle, used for cutting tools, while low-carbon steel is softer and more easily shaped, used for car bodies
• Stainless steel, an alloy of iron, carbon, chromium, and nickel, is hard and resistant to corrosion
• Alloys of aluminium are low density, making them useful for aeroplane bodies
• NPK fertilizers contain compounds of nitrogen, phosphorus, and potassium, which improve agricultural productivity by helping plants grow larger and more rapidly
• NPK fertilizers are produced in large industrial facilities where a variety of raw materials are processed together to produce the exact fertilizer required
• Compounds in NPK fertilizers:

  • Nitrogen compound: main compound is ammonium nitrate (NH₄NO₃), produced using the Haber process to create ammonia, then reacting the ammonia with nitric acid
  • Potassium compound: comes from potassium chloride or potassium sulfate, mined from the ground and used directly without further processing
  • Phosphorus compound: phosphate rock is chemically processed with nitric acid, sulfuric acid, or phosphoric acid to create phosphoric acid, calcium phosphate, calcium sulfate, single super phosphate, or triple super phosphate, which are used in NPK fertilizers
• In the lab, the production of ammonium nitrate involves reacting ammonia with nitric acid in a neutralization reaction using dilute solutions for safety, while in industry, concentrated nitric acid and gaseous ammonia are used, with the reaction being highly exothermic and providing energy for later stages
• The Haber process is used for the manufacture of ammonia
• Raw materials for the Haber process are nitrogen and hydrogen
• Nitrogen can be extracted from the air, while hydrogen can be produced by reacting methane with steam
• In the Haber process, purified nitrogen and hydrogen are passed over an iron catalyst at around 450 degrees Celsius and 200 atmospheres pressure
• The Haber process is a reversible reaction, where some of the produced ammonia can break back down into nitrogen and hydrogen
• Le Chatelier's principle is applied to choose the conditions for the Haber process to maximize the yield of ammonia
• In the Haber process, a relatively cool temperature of 450 degrees Celsius is chosen as a compromise to achieve a relatively fast rate and a relatively high yield of ammonia
• The iron catalyst used in the Haber process increases the rate of the reaction, but has no effect on the position of the equilibrium
• High pressure in the Haber process pushes the equilibrium to the right-hand side, increasing the yield of ammonia
• A compromise pressure of 200 atmospheres is chosen for the Haber process, as very high pressures are expensive and dangerous
• Manufacturing plastics

  1. Produced using chemicals from crude oil

  2. Oil extraction, transportation, separation, cracking, and polymer production require large amounts of energy generated by burning fossil fuels