Assertion (A) : In summer a block of iron is hotter than a block of wood. Reason (R) : The relative density of iron is more than the relative densi ty of wood

Assertion (A) is true because iron has a lower specific heat capacity (approx. 450 J/kg°C) compared to wood (approx. 1700-2000 J/kg°C) [t1, t4]. Under identical solar radiation, iron absorbs heat more efficiently and experiences a higher temperature rise for the same amount of energy [t1, t5]. Additionally, iron's high thermal conductivity makes it feel hotter when touched as it transfers heat to the skin faster [t3, t7]. Reason (R) is also true; iron is significantly denser than wood, and relative density is a measure of this heaviness [c2, t2]. However, (R) is not the correct explanation for (A). The temperature difference is primarily governed by specific heat capacity and thermal conductivity, not density itself [t1, t5]. While density is a component of volumetric heat capacity, it does not directly explain why iron reaches a higher temperature than wood under sunlight [t1, t2].

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 9: The Amazing World of Solutes, Solvents, and Solutions > 9.4 Why Do Objects Float or Sink in Water? > p. 140
2. [2] https://www.yourhome.gov.au/passive-design/thermal-mass