Metals are good conductors of thermal energy because energy is transferred…

The idea

In a metal, the giant lattice contains positive metal ions and delocalised electrons. The delocalised electrons are free to move throughout the structure. When one part of a metal is heated, the electrons in that region gain kinetic energy. Because they are mobile, these electrons move quickly through the metal and transfer energy to other parts of the lattice by collisions and interactions with ions and other electrons. This allows thermal energy to pass rapidly through the metal. The same delocalised electrons are responsible for electrical conduction, which is why metals are good conductors of both electricity and thermal energy.

For example: Copper and aluminium are used in cooking pans and heat exchangers because they conduct thermal energy efficiently.

What earns the marks

• Metals contain delocalised electrons that are free to move through the lattice.
• When heated, the delocalised electrons gain kinetic energy.
• The moving electrons transfer energy through the metal to other regions.
• A named example, such as copper or aluminium used in cooking pans, can illustrate the property.

Common mistakes and how to put them right

• Saying that thermal energy is carried only by the metal ions vibrating in place.

  Put it right: The delocalised electrons are the key mobile energy carriers.

• Confusing thermal conduction with electrical conduction and describing current flow when the question asks about heating.

• Stating that electrons carry heat as a substance.

  Put it right: They transfer energy, not matter.

Exam tips

• Refer to delocalised electrons gaining kinetic energy when the metal is heated.
• Explain that the electrons move through the metal and transfer energy to other parts.
• Keep the explanation focused on thermal energy transfer, even though the same electrons also carry electrical charge.