Which best describes why a liquid needs a container when a solid does not?

The difference in the behavior of liquids and solids regarding containment can be attributed to their molecular structure and bonding characteristics.

1. Molecular Arrangement: In solids, molecules are tightly packed in a fixed arrangement, allowing them to hold a definite shape. This rigidity means that solids do not require a container to maintain their form. Conversely, in liquids, molecules are more loosely packed and can move freely, which means they do not have a specific shape and will take the shape of their container.

2. Intermolecular Forces: The forces between molecules in solids are strong enough to keep them in place, allowing solids to maintain a fixed volume and shape. In liquids, however, these intermolecular forces are weaker, allowing molecules to slide past one another, which results in a lack of a definitive shape.

3. Volume and Shape: While both solids and liquids have a definite volume, only solids maintain a definite shape without the aid of confinement. Liquids will expand to fill the shape of their container, demonstrating their fluid nature.

In summary, the need for a container for liquids arises from their molecular structure, which allows for movement and lack of fixed shape, whereas solids retain their shape due to their tightly packed molecular arrangement.