Here's why:
* Water particles are always the same size. A water molecule (H₂O) is a specific arrangement of two hydrogen atoms and one oxygen atom. This arrangement doesn't change when water changes states.
* Volume change is about spacing, not size. When water changes from a liquid to a gas (water vapor), the individual water molecules spread much further apart. This increased spacing is what leads to the dramatic volume increase, not a change in the size of the molecules themselves.
Think of it like this: imagine a crowd of people packed tightly together in a small room (liquid). If they all spread out and move to a much larger space (gas), the overall volume they occupy increases, but the size of each individual person (water molecule) remains the same.
