Which state of matter would you find individual molecules in a fixed structure?

In a solid state of matter, individual molecules are arranged in a fixed, orderly structure. This arrangement is characterized by strong intermolecular forces that keep the molecules closely packed together, allowing them to vibrate but not move freely. This fixed structure is what gives solids their definite shape and volume. Examples of solid substances include ice, metals, and crystals, where the molecular organization contributes to the material's stability and rigidity.

In contrast, liquids have more freedom of movement among molecules, allowing them to flow and take the shape of their container while maintaining a fixed volume. Gases consist of molecules that are widely spaced with minimal intermolecular forces, resulting in them filling the entire volume of their container and assuming its shape. Plasma is a high-energy state of matter where electrons are free from their nuclei, leading to ionized gas behavior with charged particles. Therefore, among the options provided, the solid state is the only one where individual molecules exist in a fixed structure.