AQA GCSE · Question 07.1 · Bonding structure and the properties of matter
This question is about iron.
Iron is a metal.
Describe how iron conducts thermal energy.
How to approach this question
1. Recall the structure of metals. What kind of particles are present and how are they arranged?
2. What specific particles are responsible for the conduction of heat (and electricity) in metals?
3. Describe how these particles transfer energy when one part of the metal is heated.
Full Answer
Iron has a giant metallic structure containing delocalised electrons. These electrons are free to move throughout the structure. When heated, the electrons gain kinetic energy and move faster, transferring this energy by colliding with other electrons and ions.
Metals like iron have a giant metallic lattice structure. This structure consists of a regular arrangement of positive metal ions surrounded by a 'sea' of delocalised electrons. These electrons are not associated with any single atom and are free to move throughout the entire structure.
When one end of an iron bar is heated, the delocalised electrons at that end gain kinetic energy and move faster. They then travel through the lattice, colliding with other electrons and the positive ions, transferring the kinetic energy rapidly. This process allows thermal energy to be conducted efficiently from the hot end to the cold end.
Common mistakes
✗ Mentioning ions vibrating - this happens, but the main mechanism for thermal conduction in metals is the movement of delocalised electrons.
✗ Confusing metallic bonding with ionic or covalent bonding.
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