Final answer:
Gases and plasma are the forms of matter that lack a definite volume and shape. Solids have fixed shapes and volumes, while liquids have fixed volumes but take the shape of their containers.
Step-by-step explanation:
The physical forms of matter that have neither a definite volume nor a definite shape are gases and plasma. These states of matter are fluid in nature, meaning that their molecules can move freely and will fill the container in which they are held. Solids, on the other hand, have both a definite shape and volume, while liquids have a definite volume but no definite shape, conforming to the shape of their container.
Based on this information, we can determine that gases, such as O₂(g), fully expand to fill a container regardless of its size or volume. This property of gases is markedly different from solids, which have their molecules packed closely together, maintaining a fixed shape and volume, and from liquids that have closely packed molecules but take on the shape of their container. Plasmas are similar to gases in that they also have neither a definite shape nor a definite volume.