Gas.
The volume of a gas is subject to change with temperature and pressure.
Solids are the only phase of matter which have a fixed shape and volume.
Solid.
gas
a solide has a shape of its shape and volume
a solide has a shape of its shape and volume
liquid
This is a good working description of the gaseous phase of matter. A sample of gas will assume the shape and volume of its container, so the sample has no shape or volume of its own.
A liquid has a variable shape and a definite volume.
a liquid
liquid
Gas