Final answer:
Molecules or atoms in a solid are closely packed and vibrate around fixed positions due to strong intermolecular forces, giving solids a fixed shape and volume. The kinetic molecular theory describes this behavior and the effect of temperature changes on particle motion.
Step-by-step explanation:
Describe the Motion of Molecules in a Solid:
In a solid state, the molecules or atoms are closely packed, often in an orderly arrangement, which results in a definite structure. These particles are not static; instead, they undergo vibrational motion around their fixed positions. Despite the motion, the particles in a solid do not have enough energy to move past one another due to the strong intermolecular forces holding them in place. This restricted movement is why solids have a fixed shape and volume and are incompressible and the most dense of the three states of matter.
The kinetic molecular theory explains the behavior of particles in different states of matter and is particularly useful in understanding how the motion of particles changes as a solid transforms to a liquid (melting) or a solid gains heat (temperature increase).
As more heat is applied to a solid, the vibrational motion increases until the particles have enough energy to overcome the intermolecular forces and move freely, leading to a phase change into a liquid. Conversely, when the temperature is low, the motion of particles is minimized, and they remain in a solid form, with a fixed and defined shape independent of the container they occupy.