Answer:
If it can change shapes easily.
Explanation:
A fixed volume eliminates gas as a possible state of matter, therefore leaving liquid and solid.
If the substance can easily change shape, it is a liquid. If it cannot change shape, then it is a solid.
Another way to determine the state of matter is through particle movement.
If particles slip past each other, it is a liquid. If particles vibrate in place, it is a solid.