It is a gas because the particles of the substance have the highest speeds.
There are three states of matter and these are;
The difference between the states of matter lies in;
Solid particles have the greatest magnitude of intermolecular forces and consequently a negligible average speed of particles.
In liquids, the magnitude of intermolecular forces is less than in solids hence the average speed of liquid particles is greater than that of solids.
In gases, the intermolecular forces are negligible hence the speed of gas particles is maximum.
Therefore, Y is a gas because the particles of the substance have the highest speeds.
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