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⚛️ Physics  ·  Thermal Properties of Matter  ·  NEET & JEE

A liquid cools from 70°C to 60°C in 5 minutes and from 60°C to 50°C in 8 minutes, with the room temperature constant. Using Newtons law of cooling (approximate form), this tells us that:

Answer: The room temperature is below 50°C, consistent with the slower cooling rate at lower temperature difference.

  • A The room temperature is around 70°C, equal to the liquid's starting temperature in typical laboratory settings
  • B The room temperature is below 50°C, consistent with the slower cooling rate at lower temperature difference
  • C The specific heat capacity of the liquid changed partway through cooling under usual circumstances according to most researchers
  • D The given data is inconsistent with Newton's law of cooling largely in the majority of cases studied as widely reported

Correct answer: B. The room temperature is below 50°C, consistent with the slower cooling rate at lower temperature difference

Explanation: Since the cooling slows down as the liquid temperature approaches the surroundings, the smaller temperature drop in a longer time (60 to 50 in 8 min vs 70 to 60 in 5 min) is expected behaviour consistent with Newtons law of cooling, with room temp below 50°C.

Heating Curve: Ice → Water → SteamHeat added (Q)T (°C)ice warms (-ve→0°C)melting (0°C, latent heat)water warms (0→100°C)boiling (100°C, latent heat)FLAT regions = phase change (all heat goes into breaking bonds, NOT raising temperature)

During a phase change (melting or boiling), temperature stays constant while heat is absorbed entirely as latent heat (Q=mL); temperature only rises again once the substance is fully in its new phase.

Concept context

Temperature scales, thermal expansion, calorimetry, and the three modes of heat transfer including radiation laws.

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