why gases do not have a definite shape but a definite volume
The correct answer and explanation is:
The correct answer is: Gases do not have a definite volume, only a definite shape if confined.
However, this needs clarification because gases do not have a definite shape or volume. They take the shape and volume of their container.
Explanation:
Gases do not have a definite shape because their particles move freely and randomly in all directions. Unlike solids, where particles are tightly packed in a fixed arrangement, or liquids, where particles are close but can flow, gas particles are far apart and move independently. This freedom allows gases to expand and fill the shape of any container they occupy, so their shape is always that of the container.
Similarly, gases do not have a definite volume. The particles in a gas are spaced widely apart with large amounts of empty space between them. Because of this, gases can be compressed or expanded easily. When placed in a container, a gas will expand or compress to fill the entire volume available. This behavior contrasts with solids, which have a fixed volume and shape, and liquids, which have a fixed volume but take the shape of the container.
In summary, gases lack both a definite shape and volume because their particles have high kinetic energy, move independently, and are widely spaced. They respond to the boundaries of their containers by expanding or compressing to fit both shape and volume.
This is why gases are described as having neither a definite shape nor a definite volume. They are highly compressible and take on the shape and volume of their container.