C15

• What does iron react with to form rust?

  Oxygen and water
• What is the chemical formula for rust?

  Fe₂O₃
• Why does rust make iron structures weaker?

  Rust is brittle and more porous
• What accelerates the rusting process?

  Presence of salt
• What is the word equation for rusting?

  • Iron + Oxygen + Water → Hydrated Iron(III) Oxide
• What is the symbol equation for rusting?

  4Fe + 3O₂ + 6H₂O → 2Fe₂O₃·3H₂O
• What does gaining oxygen represent in rusting?

  Oxidation
• What is the ionic equation for rusting?

  4Fe → 4Fe³⁺ + 12e^-
• What are methods to prevent rusting?

  • Coat with oil, grease, paint, or plastic
  • Use a less reactive metal
  • Galvanizing with zinc
• What is galvanizing?

  Coating iron with zinc
• How does zinc protect iron in galvanizing?

  Zinc reacts with oxygen first
• What is stainless steel made from?

  Iron, nickel, chromium, and carbon
• Why is stainless steel expensive?

  Due to the alloying metals used
• What was the first alloy produced by humans?

  Bronze
• What metals make up bronze?

  Copper and tin
• What is bronze commonly used for?

  Making statues and ornaments
• What is brass an alloy of?

  Copper and zinc
• What is cupro-nickel used for?

  Manufacturing 'silver' coins
• What are the types of gold and their carat values?

  • 9 Carat: 37.5%
  • 14 Carat: 58.3%
  • 18 Carat: 75%
  • 22 Carat: 91.6%
  • 24 Carat: 100%
• Why is gold often alloyed with other metals?

  To spread it further due to scarcity
• What are the properties and uses of different alloys?

  • Bronze: Hardness, strong; used for axes, needles, sculptures
  • Brass: Bright yellow, hard; used for keys, decorative items
  • Gold: Bright yellow, does not tarnish; used for coins, jewelry, electrical contacts
• What is the process of extracting iron from its ore called?

  Smelting
• What is the main component added to the blast furnace?

  Limestone, coke, and haematite
• What happens when hot air is blasted into the blast furnace?

  Carbon reacts to form carbon dioxide
• What does carbon monoxide do in the blast furnace?

  Reduces iron ore to form iron
• What is the byproduct collected at the bottom of the blast furnace?

  Slag
• What is pig iron?

  Iron with a high carbon content
• Why is pig iron brittle?

  Due to its high carbon content
• How can the brittleness of pig iron be overcome?

  By removing carbon and alloying
• What is carbon steel?

  Alloy of iron with small carbon amounts
• What are the types of steel and their properties?

  • Stainless Steel: Does not rust; used for cookware, cutlery, tools
  • High Carbon Steel: Very hard; used for drills, sword edges, scalpels
  • Low Carbon Steel: Ductile and malleable; used for car panels, structural steel
• What is the most important alloy of iron?

  Steel
• How long has steel production been practiced?

  For thousands of years
• What are the two main factors that determine the final properties of a polymer?

  The monomer from which it is made and the conditions used to make it
• How can polyethene be made into a soft, flexible polymer or a hard, tough polymer?

  By controlling the amount of side branches in the polymer chains
• What are the two main types of plastics based on their behavior when heated?

  Thermosoftening plastics and thermosetting plastics
• How do thermosoftening plastics and thermosetting plastics differ in their behavior when heated?

  Thermosoftening plastics soften when heated and can be remoulded, while thermosetting plastics do not soften and cannot be remoulded
• What are the main raw materials used to make glass?

  • Sand
  • Limestone (Calcium carbonate)
  • Soda (Sodium carbonate)
• Why is the heat energy required to melt the raw materials the expensive part of making glass?

  Because temperatures over 1400°C need to be reached to melt the raw materials
• What is the key difference between the atomic structure of glass and other solids?

  The atoms in glass do not arrange themselves into neat patterns like other solids