For a substance to begin to boil, it must have an increase in kinetic energy, either due to an increase in temperature or a decrease in pressure. Now, by having greater kinetic energy, the average speed of the molecules will be greater, there will also be greater collisions between the molecules and they will begin to move away. Therefore, the correct option will be: The particles move more quickly and spread far apart.
Answer: C. The particles move more quickly and spread far apart.