Final answer:
During changes from a gas to a liquid state, particles decelerate. This process is associated with a decrease in the average kinetic energy of the particles and a temperature drop, resulting in slower molecular movement. Therefore, the correct option is B.
Step-by-step explanation:
As matter changes state from gas to liquid, the statement 'The particles slow down' is true. In a gaseous state, particles fly about freely at high speed, continually bumping into one another and their surroundings. However, when changing to a liquid state, these particles slow down and can slide smoothly past one another, while still being held together by mutual attraction.
Bigger molecules move slower than lighter ones and increasing or decreasing temperature affects the energy in the medium, hence affecting molecular movement. Thus, the state change from gas to liquid involves a decrease in the average kinetic energy of the particles, causing a decrease in temperature and resulting in a slower pace of molecular movement.
Learn more about State change