Students want to impress their physics teacher by writing an essay that describes the heating of ice at a temperature below 0°C to steam at a temperature above 100°C. Write such a paragraph using the terms energy, temperature, and phase change. Be sure to include a description of the five major stages.

Energy is required to change the phase of a substance, such as the energy to break the bonds between molecules in a block of ice so it may melt.

During a phase change energy my be added or subtracted from a system, but the temperature will not change. The temperature will change only when the phase change has completed.

The heat Q required to change the phase of a sample of mass m is given by

Q

=

mL

f

(melting or freezing) and

Q

=

mL

v

(evaporating or condensing), where Lf and Lv are the latent heat of fusion and the latent heat of vaporization, respectively.

Key Terms

latent heat of fusion: the energy required to transition one unit of a substance from solid to liquid; equivalently, the energy liberated when one unit of a substance transitions from liquid to solid.

latent heat of vaporization: the energy required to transition one unit of a substance from liquid to vapor; equivalently, the energy liberated when one unit of a substance transitions from vapor to liquid.

sublimation: the transition of a substance from the solid phase directly to the vapor state such that it does not pass through the intermediate, liquid phase

The Danes were enjoying prosperity, after having conquered many other tribes through battle, Shield Sheafson as their leader. He is described as a 'scourge of many tribes, / a wreaker of mead-benches, rampaging among foes' (lines 4-5).

Explanation: