A change of ______ will always occur with a change of phase.

A change of ______ will always occur with a change of phase.

• A. State
• B. Temperature
• C. Volume
• D. Density

Answer: (A)

A phase change is a change in the state of matter (solid, liquid, or gas). That change in state is what defines a phase change, because the arrangement and interaction of molecules shift as the substance moves from one phase to another. Temperature does not have to change during the transition—during melting or boiling, heat goes into breaking or forming intermolecular bonds (latent heat) while the temperature stays constant until the phase change completes. Volume and density can vary with different substances and conditions, but they do not change universally with every phase change, so they aren’t guaranteed indicators. Therefore, the aspect that always accompanies a phase change is a change of state.

A phase change is a change in the state of matter (solid, liquid, or gas). That change in state is what defines a phase change, because the arrangement and interaction of molecules shift as the substance moves from one phase to another. Temperature does not have to change during the transition—during melting or boiling, heat goes into breaking or forming intermolecular bonds (latent heat) while the temperature stays constant until the phase change completes. Volume and density can vary with different substances and conditions, but they do not change universally with every phase change, so they aren’t guaranteed indicators. Therefore, the aspect that always accompanies a phase change is a change of state.