The shape and volume of a gas are variable. Unlike solids and liquids, gases do not have a definite shape or fixed volume. This means that a gas will expand to fill the container it occupies, taking on the shape of that container as well.
To understand why, we need to consider the behavior of gas particles. Gas particles are spread far apart and move freely at high speeds. This freedom of movement allows gases to disperse and fill any available space. When a gas is placed in a container, it expands to fill the entire container, regardless of its size or shape.
In contrast, solids have a fixed shape and volume because their particles are closely packed together in a structured arrangement, while liquids have a fixed volume but take the shape of their container because their particles are close but can slide past each other. Therefore, gases are unique in that both their shape and volume are flexible and adaptable to their environment.