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Zorluk: OrtaLatent Heat and Changes of State

When a pure substance undergoes a change of state from liquid to vapor at its boiling point under constant atmospheric pressure, the added thermal energy increases the average kinetic energy of the molecules, causing its temperature to rise continuously until vaporization is complete.

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The statement is False. During a phase change at boiling point, thermal energy acts as latent heat, increasing the potential energy of the molecules to break intermolecular bonds while keeping average kinetic energy and temperature constant.
During boiling under constant atmospheric pressure, all absorbed thermal energy is utilized as latent heat of vaporization to do work against intermolecular forces, increasing molecular potential energy. Because temperature measures average kinetic energy, the temperature remains strictly constant until the phase change is complete.

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1
Identify the nature of heat added during a state change at constant pressure.
The added heat is latent heat of vaporization.
Heat added during a change of phase at boiling point does not produce a temperature change.
2
Relate molecular kinetic energy to temperature.
Temperature is directly proportional to the average translational kinetic energy of the molecules.
If kinetic energy increases, temperature must rise; since temperature remains constant during boiling, average kinetic energy does not change.
3
Determine the destination of the absorbed thermal energy.
Energy is stored as molecular potential energy.
The energy is spent overcoming attractive intermolecular forces to separate molecules from the liquid state into the gaseous state.

Anahtar Kavram

Constant temperature and molecular energy changes during phase transition
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Konular

Latent Heat and Changes of State

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