Question

During segment D, the temperature is not changing even though the heat source is still going. Is this process endothermic or exothermic? Explain why the heat is not changing the temperature of the substance.

Answer 1

This is the heating curve of water. at segment D the water is boiling. Boiling is an endothermic process because energy is absorbed. The temperature isn't changing because heat is used to break intermolecular bonds instead of increasing the kinetic energy of the particles and raising the temperature.