\- What is saturation density? How does it change when the temperature increases?

Saturation density is the maximum density that a substance can attain under specific conditions, such as temperature and pressure. It is an important concept in the study of thermodynamics, as it is involved in phase transitions, vapor-liquid equilibria, and other phenomena.

Generally, the saturation density of a substance is highly dependent on its temperature. Here, we're interested in how the saturation density changes when the temperature increases.

When it comes to liquids, as the temperature increases, the saturation density usually decreases. This can be explained by the fact that as the temperature increases, the average kinetic energy of the particles increases as well. This added energy causes the particles to move faster, expanding the liquid and lowering its density.

The relationship between saturation density and temperature for gases is more complex. For an ideal gas, the saturation density is inversely proportional to temperature, since density is proportional to pressure and temperature is directly proportional to pressure. However, real gases exhibit more complicated behavior, notably at higher pressures and lower temperatures, where non-ideal effects become significant and deviate from simple relations. To sum up, the saturation density is highly dependent on the temperature of a substance. In liquids, as the temperature increases, the saturation density generally decreases. In gases, the relationship between saturation density and temperature is more complex, with ideal gases showing an inverse proportionality, while real gases exhibit more complicated behavior.