Which statement best describes a sample of gas?
A) A gas has a definite volume and a definite shape.
B) The volume and the shape of a gas are determined by its container.
C) A gas has a definite volume, but its shape is determined by its container.
D) The volume of a gas is determined by its container, but it has a definite shape.
The correct answer and explanation is :
The correct answer is:
B) The volume and the shape of a gas are determined by its container.
Explanation:
In the context of the behavior of gases, we need to understand their fundamental properties in relation to their shape, volume, and the influence of external factors such as containers.
- Shape of a Gas: Unlike solids and liquids, gases do not have a definite shape. Instead, they take the shape of whatever container they are placed in. This happens because gas molecules are in constant motion and have much more space between them compared to solids and liquids. The lack of attractive forces between gas molecules allows them to spread out and fill the container completely, regardless of its shape. Therefore, a gas adopts the shape of the container it occupies.
- Volume of a Gas: Similar to shape, the volume of a gas is also determined by the volume of the container it is in. A gas will expand to fill any space available to it. The gas molecules move freely in all directions, and as they collide with the walls of the container, they distribute themselves throughout the entire space. Therefore, the volume of the gas is directly dependent on the volume of its container, and not the intrinsic properties of the gas itself. This is a key characteristic that differentiates gases from solids and liquids, which have fixed volumes.
- Comparison to Other States of Matter: In contrast, solids have both a fixed volume and a fixed shape due to the tightly packed arrangement of their molecules. Liquids, while having a fixed volume, do not have a fixed shape and take the shape of their container, similar to gases, but their molecules are still closer together than those in gases, which means their volume remains constant while the shape adapts to the container.
In summary, B is the correct choice because gases do not have a definite shape or volume on their own; both are determined by the shape and volume of the container they occupy.