Which factor does not change when heat is added or removed during a phase change?

Which factor does not change when heat is added or removed during a phase change?

• A. Heat content
• B. Temperature
• C. Pressure
• D. Total energy

Answer: (B)

During a phase change, the temperature remains constant even as heat is added or removed. This phenomenon occurs because the energy being supplied or removed is used to overcome intermolecular forces rather than raising the temperature of the substance. For instance, when ice melts to form water, the temperature remains at 0 degrees Celsius until all the ice has melted, despite the addition of heat. Similarly, during boiling, water remains at 100 degrees Celsius until it has all turned to steam, even though heat is continuously being applied. In contrast, the heat content, pressure, and total energy of the substance will change during a phase transition. Heat content reflects the total amount of thermal energy present, which increases as heat is added. The total energy changes as the system transitions between states, while the pressure might change depending on the conditions surrounding the phase change. However, the defining characteristic of a phase change is that its temperature does not vary until the phase transition is fully completed.

During a phase change, the temperature remains constant even as heat is added or removed. This phenomenon occurs because the energy being supplied or removed is used to overcome intermolecular forces rather than raising the temperature of the substance. For instance, when ice melts to form water, the temperature remains at 0 degrees Celsius until all the ice has melted, despite the addition of heat. Similarly, during boiling, water remains at 100 degrees Celsius until it has all turned to steam, even though heat is continuously being applied.

In contrast, the heat content, pressure, and total energy of the substance will change during a phase transition. Heat content reflects the total amount of thermal energy present, which increases as heat is added. The total energy changes as the system transitions between states, while the pressure might change depending on the conditions surrounding the phase change. However, the defining characteristic of a phase change is that its temperature does not vary until the phase transition is fully completed.