Answer: joule.
- A joule
- B calorie
- C kelvin
- D watt
Correct answer: A. joule
Explanation: Heat is energy, measured in joules (J).
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.