Answer: 40°C.
- A 35°C
- B 40°C
- C 45°C
- D 50°C
Correct answer: B. 40°C
Explanation: T = (100·20 + 50·80)/150 = (2000 + 4000)/150 = 40°C.
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.