Final answer:
The physical state of a substance is determined by the interplay of kinetic energy and intermolecular forces (IMFs). Temperature changes affect the kinetic energy of particles, leading to changes in state as IMFs are either overcome or enforced. Increasing pressure also affects these forces, hence the physical state.
Step-by-step explanation:
The relation between the intermolecular forces present within a substance and the temperatures associated with changes in its physical state is paramount to understanding kinetic molecular theory. The physical state of a substance (solid, liquid, or gas) reflects the balance between the kinetic energy (KE) of its particles and the intermolecular forces (IMFs) that attract them together.
At low temperatures, IMFs can dominate, holding particles in a fixed arrangement (solid), whereas at higher temperatures, the increased KE can overcome the IMFs, allowing particles to move past each other (liquid) or completely overcome these forces (gas).
Changes in physical state can thus be induced by altering the temperature, which affects the kinetic energy of the particle. For example, heating a substance increases its kinetic energy, which can lead to a phase change from solid to liquid (melting) and from liquid to gas (vaporization) as the IMFs are overcome.
Conversely, cooling a substance reduces the kinetic energy, enabling the IMFs to take over and potentially turn a gas to a liquid (condensation) or a liquid into a solid (freezing).
Increasing the pressure on a substance can similarly change its physical state by forcing the molecules closer together, which increases the strength of the intermolecular forces, thereby affecting the phase of the substance.