Final answer:
The representation of a molecular liquid at low and high temperatures involves showing molecules with short arrows for their velocities at lower temperatures due to less kinetic energy, and longer velocity arrows at higher temperatures due to increased energy. As temperature increases, the energy level diagrams and PV diagrams reflect the increased average kinetic energy and spacing between molecules.
Step-by-step explanation:
To visualize the representation of a molecular liquid at different temperatures, let's consider the molecular motion. At lower temperatures, molecules move more slowly and are closer together. If we were to draw this, we would have molecules with shorter arrows representing their velocities, as the kinetic energy is lower. At higher temperatures, the opposite occurs: the molecules move faster and are spaced further apart, which would be represented by longer arrows indicating greater velocities due to increased kinetic energy.
For example, taking the kinetic energy distribution curve graph, shown at temperatures 300 Kelvin (purple line) and 400 Kelvin (green line), we can understand that as temperature increases, a larger fraction of molecules has higher kinetic energy. This increase in energy can lead to changes in phase from solid to liquid (melting) or from liquid to gas (vaporization), depicted by the purple arrows which indicate heating. Conversely, the green arrows signify the cooling processes, such as gas condensing into liquid or freezing into a solid.
Another representation could be through energy level diagrams or PV diagrams. In the case of a liquid heating up (as represented in Figure 13.28 and 2.8 pV diagrams), the spacing between molecules increases and the kinetic energy distribution shifts to represent a higher average kinetic energy amongst the particles, while the opposite occurs when the liquid cools down.