Which one among the following statements about thermal conductivity is correct?

Thermal conductivity measures a material's intrinsic ability to conduct heat. Metals, such as steel, are excellent conductors because they allow heat to pass through them easily due to their atomic structure and electron mobility. According to standardized data, steel has a thermal conductivity of approximately 51.0 W/m·K. In contrast, liquids like water have significantly lower thermal conductivity, measured at approximately 0.58 to 0.60 W/m·K. Wood is classified as a poor conductor or insulator because its porous structure, often filled with air, inhibits heat transfer. The thermal conductivity of wood typically ranges from 0.12 to 0.25 W/m·K. Therefore, the correct ranking from highest to lowest thermal conductivity is Steel > Water > Wood, as metals conduct heat much faster than liquids, which in turn conduct better than insulating solids like wood.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 4: The World of Metals and Non-metals > Activity 4.3: Let us investigate > p. 47