Alloys

• What is an alloy?

  An alloy is a mixture of two or more elements, at least one of which is a metal.
• How can the properties of a metal be modified?

  By mixing it with another substance to form an alloy.
• What explains the high melting and boiling points of metals?

  The structure of metals.
• Why are many pure metals too soft for many uses?

  Because they can be made harder by adding another element to form an alloy.
• What happens when a small amount of tungsten is added to iron?

  It makes tool steel, which is harder than pure iron.
• What are the three types of steel mentioned?

  • Mild steel: Carbon and iron, easy to bend and pull into wires.
  • Tool steel: Tungsten and iron, hard, can be heated to high temperatures.
  • Stainless steel: Chromium and iron, hard, does not rust easily.
• What is the structure of a pure metal in the solid state?

  A pure metal has a giant metallic structure with atoms arranged in layers.
• What happens to the layers of atoms in a pure metal when a force is applied?

  The layers may slide over each other.
• Why are pure metals considered soft?

  Because a small force is needed to make the layers slide over each other.
• How does the presence of different sized atoms in an alloy affect its hardness?

  It distorts the layers of atoms, requiring a greater force to slide them over each other.
• What is the reason steel is harder than pure iron?

  Steel contains atoms of other elements that distort the layers of atoms in pure iron.
• What is the effect of adding different elements to pure metals in terms of their properties?

  • Increases hardness and strength.
  • Alters melting and boiling points.
  • Enhances resistance to corrosion.