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Difficulty: MediumThermodynamics and Heat

Different materials transfer thermal energy by conduction at significantly different rates. Arrange the following substances in order of increasing thermal conductivity, starting from the poorest conductor (best thermal insulator) and ending with the best thermal conductor.

  1. 1Trapped air
  2. 2Liquid water
  3. 3Iron
  4. 4Copper

Answer

Trapped air, Liquid water, Iron, Copper
Thermal conductivity measures a material's ability to conduct heat. Gases like trapped air have widely dispersed molecules and are the poorest conductors. Liquids like water have closer molecules and conduct heat moderately better than gases. Solid metals conduct heat rapidly due to free electrons, with copper exhibiting superior conduction compared to iron.

Step-by-Step Solution

1
Identify the state of matter and thermal mechanism for each substance
Trapped air is a gas, liquid water is a non-metallic liquid, while iron and copper are solid metals.
Thermal conduction occurs through particle collisions and free electron movement, which depends heavily on state of matter and atomic bonding.
2
Rank the non-metals based on molecular density
Trapped air has the lowest thermal conductivity (k≈0.026 W/(m⋅K)k \approx 0.026\text{ W/(m}\cdot\text{K)}), followed by liquid water (k≈0.6 W/(m⋅K)k \approx 0.6\text{ W/(m}\cdot\text{K)}).
Gases have large intermolecular distances leading to rare collisions, whereas liquids are denser and transfer kinetic energy more readily.
3
Rank the metals based on electronic thermal transport
Iron has a thermal conductivity of approximately 80 W/(m⋅K)80\text{ W/(m}\cdot\text{K)}, whereas copper has a thermal conductivity of approximately 400 W/(m⋅K)400\text{ W/(m}\cdot\text{K)}.
Both metals conduct heat via free valence electrons, but copper's electronic structure allows significantly higher conductivity.

Key Concept

Thermal Conductivity of Materials
Estimated Time:1m 0s
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Topics

Thermodynamics and Heat

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