In which state of matter are particles most tightly packed together?

In a solid state of matter, particles are packed together most tightly compared to liquids, gases, and plasmas. This close packing occurs because the particles in a solid are in a fixed position and can only vibrate about these positions. This arrangement allows solids to maintain a definite shape and volume.

In contrast, in liquids, the particles are still close together but can move past one another, which allows liquids to take the shape of their container while still retaining a fixed volume. In gases, the particles are much farther apart and move freely, filling the volume of their container. Plasma consists of ionized particles and also has a high degree of spacing between particles due to the high energy levels, allowing them to move independently. Thus, the solid state is characterized by the tightest packing of particles, which directly contributes to its structural integrity and resistance to compression.