Using materials

• What happens when metals oxidise in air?

  They react with oxygen to form metal oxides
• What is the reaction equation for sodium oxidising?

  4Na(s) + O2(g) → 2Na2O(s)
• Which metal does not oxidise in air at all?

  Gold
• What happens to a metal during corrosion?

  The metal becomes weaker and may turn to oxide
• What three components are needed for rusting to occur?

  Iron, oxygen, and water
• What does the rusting experiment demonstrate about rusting conditions?

  • Oxygen and water are both required for rusting
  • Rusting does not occur without either component
• What is the key fact about rusting of iron or steel objects?

  They only rust if oxygen and water are present
• What happens to iron when it forms rust?

  Iron is oxidised
• What is one method to prevent rusting?

  Removing substances that cause rusting
• How can rusting be prevented by keeping oxygen away from iron?

  Store metal in unreactive nitrogen or argon
• What is a desiccant?

  A substance that absorbs water vapor
• What are the physical barriers to prevent rusting?

  • Painting
  • Oiling and greasing
  • Coating with plastic
• Why is oiling a bike chain preferred over painting for rust prevention?

  Oiling allows movement and prevents rust
• What does electroplating involve?

  Using electrolysis to apply a metal layer
• What is the role of the cathode in electroplating?

  The iron or steel object being plated
• What is the anode in the electroplating process?

  The plating metal used in the process
• What does the electrolyte contain in electroplating?

  It contains ions of the plating metal
• How does electroplating improve corrosion resistance?

  By adding a protective metal layer
• What is sacrificial protection in rust prevention?

  Using a more reactive metal to protect iron
• Why does a more reactive metal protect iron from rusting?

  It oxidizes more readily than iron
• What happens to the sacrificial metal after it corrodes?

  It can be replaced easily
• Why does the nail wrapped in magnesium not rust?

  Magnesium is more reactive than iron
• Why does the nail wrapped in copper rust more than the nail alone?

  Iron oxidizes more readily than copper
• What is galvanization?

  Coating iron with zinc for protection
• How does the zinc layer in galvanization protect iron?

  Stops oxygen and water from reaching iron
• What happens if the zinc layer is scratched?

  Zinc still protects iron as sacrificial metal
• Why does the inside of a steel food can rust quickly if the tin layer is broken?

  Oxygen and water reach the iron directly
• What is an alloy?

  A mixture of two or more elements
• Why are most metals in everyday use alloys?

  Alloys have enhanced properties for various uses
• What is bronze made of?

  Copper and tin
• What was the first alloy made by humans?

  Bronze
• What are some common uses of bronze?

  Statues, bells, and coins
• What is brass made of?

  Copper and zinc
• What are some uses of brass?

  Musical instruments, door knobs, locks, taps
• What is a key property of gold?

  It is very soft and malleable
• Why does gold resist corrosion?

  It is very unreactive
• Why are visors on space helmets coated with gold?

  To reflect sunlight while allowing visibility
• What is the purpose of alloying gold for jewellery?

  To make it stronger while staying shiny
• How is the proportion of gold in an alloy measured?

  In carats
• What percentage of gold is in 24 carat gold?

  100%