Which type of matter has a changeable shape but maintains a definite volume?

Liquids are characterized by having a definite volume while possessing a shape that can change depending on the container they are in. This is due to the unique arrangement of molecules in a liquid state. In liquids, the molecules are closely packed together, which allows them to maintain a constant volume. However, the intermolecular forces are not strong enough to keep the molecules in a fixed position, allowing them to move past one another and take on the shape of their container.

In contrast, solids have a definite shape and fixed volume, while gases have neither a definite shape nor a fixed volume, expanding to fill their container. Plasma, being an ionized gas, also lacks a defined shape or volume in similar ways to gases. Thus, liquids stand out for their ability to retain volume while adapting their shape.