Answer:
When 1 mole of water undergoes a change in state from liquid to gas, it means that the water molecules transition from a liquid phase to a gaseous phase. This change in state is known as vaporization or evaporation.
In the liquid phase, water molecules are closely packed together and have sufficient intermolecular forces to maintain their cohesive properties. These intermolecular forces, such as hydrogen bonding, hold the water molecules in a relatively fixed arrangement.
However, when heat energy is supplied to the system, it increases the kinetic energy of the water molecules. As the kinetic energy increases, the water molecules gain enough energy to overcome the intermolecular forces holding them together. This leads to the molecules becoming more mobile and transitioning into the gaseous phase.
In the gas phase, the water molecules are widely dispersed and have much higher kinetic energy compared to the liquid phase. They move independently of each other, filling the available space and spreading out to occupy a larger volume.
During this phase transition, the temperature remains constant until all the liquid has converted into gas. This constant temperature is known as the boiling point, and for water at standard pressure, it is 100 degrees Celsius (212 degrees Fahrenheit).
Overall, the qualitative explanation for the change in state from 1 mole of liquid water to 1 mole of gaseous water involves the absorption of heat energy, an increase in molecular kinetic energy, and the breaking of intermolecular forces to allow the water molecules to transition from a liquid to a gas.