Imagine that you move a substance from one container to another and its volume changes.

What state of matter is that substance?

liquid

gas

solid

That depends on the specific substance and the conditions under which it is being moved. If the substance changes its volume easily and flows, it is likely in the liquid state. If the substance expands to fill its container completely and does not have a fixed shape or volume, it is in the gas state. If the substance maintains a fixed shape and volume, it is in the solid state.