Final answer:
To have a constant boiling point in steam distillation, maintaining a constant pressure is necessary. The normal boiling point, which is a constant, is defined for a liquid based on the standard atmospheric pressure. Boiling points can vary with changes in external pressure, which is why they are not always the same as the normal boiling point.
Step-by-step explanation:
To ensure the boiling point in steam distillation remains constant, the requirement necessary is constant pressure. The boiling point of a liquid at which it turns into vapor is determined by the pressure of the environment. The normal boiling point is the temperature at which the vapor pressure of the liquid equals the standard atmospheric pressure of 760 mm Hg or 1 atm. In a steam distillation setup, maintaining constant pressure ensures that the boiling point remains stable.
It is important to note that the boiling point and normal boiling point are not always the same. The boiling point of a substance changes with external pressure and can be different depending on the atmospheric pressure, which may vary with location or weather conditions. However, the normal boiling point is a constant, as it is defined relative to a standard pressure.
Moreover, in the kinetic molecular theory, a solid is described as composed of particles that are closely packed together, vibrating in place, with very little movement relative to each other. This is in contrast to liquids and gases, where particles move more freely.