Answer: Particles are farther apart in gases so substance X is water vapor.
Step-by-step explanation:
Liquid state : It is a state in which the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another and thus have higher kinetic energy as compared to solids. This state has a definite volume but does not have a fixed shape. They occupy lesser volume than gases. Example: Liquid water
Gaseous state : It is a state in which the particles are loosely arranged and have a lot of space between them. They have highest kinetic energy. This state has indefinite volume as well as shape. They occupy the most volume. Example: Water vapor
As it is given that substance X has higher volume as compared to substance Y, thus we can conclude that substance X represents water vapor and substance Y represents water.