Lustre Malleability and ductility Electrical conductivity Heat conductivity Physical states General properties of metals

Metals make up about two thirds of the naturally occurring elements. There are many different mixes of metals like bronze and steel, called alloys. In this topic the physical properties of metals will be investigated and matched with their uses.

Lustre
Metals are readily identified by their most common physical property, the ability to reflect light, known as lustre. When polished most metals are silvery grey, with the notable exceptions of gold and copper, with their bright yellow/orange lustre.

Mirrors have a thin layer of metal on the back of the glass giving the mirror its ability to reflect light. The Romans and Greeks used pools of mercury, polished bronze or copper as mirrors.

Malleability and ductility
Metals are also easily distinguished from non-metals and other materials in their ductility (ability to be drawn into a wire) and malleability (the ability to be beaten into a sheet). Some metals like gold can be drawn out into wires or beaten into sheets only a few atoms thick and still retain their strength.

Copper, gold, iron, silver and aluminium are used extensively in flat sheets, foil, and wire because they are highly malleable and ductile.

Electrical conductivity
Metals conduct electricity well, a physical property not shared with most other materials. Most importantly metals can pass an electric current without being affected and changed by the electricity. Electrical conductivity combined with ductility makes metals the most suitable materials for electrical transmission wires.

Copper is used extensively in household electrical wiring, where weight is not a problem. Aluminium is used in high voltage power lines because it is much lighter than copper, while gold is used in computer chips to make electrical circuits because it resists corrosion and very thin connections can be made.

Heat conductivity
Metals also conduct heat well. The metal grid at the back of a refrigerator is made of metal so that it can transfer heat away from the fridge. Pots and pans are made of metals to allow heat from the stove to reach the food being cooked. Metals feel cold because they conduct the heat away from your hand when you touch it.

Physical states
Metals generally have high melting and boiling points and are quite hard solids. There are a few notable exceptions, being gold, silver and lead. These metals are soft and easily worked. Mercury is the only liquid metal at room temperature (25°C).

General properties of metals

• Lustre - Metals reflect light well.
• Malleable - Can be beaten into sheets.
  
• Ductile - Can be drawn out into wires.
  
• Conductors - Conduct electricity.
  
• Have high melting and boiling points - all are solids except mercury.
  
• Most are hard - can scratch softer materials.

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