Kinetic Theory & Phase Changes: Melting, Boiling, Diffusion, and Brownian Motion

Understanding States of Matter

Matter exists in different states: solid, liquid, and gas. Each state has distinct characteristics based on the arrangement and movement of its particles.

• Solids: Particles are closely packed in a fixed arrangement and vibrate in place.
• Liquids: Particles are close together but can move past each other, allowing liquids to flow.
• Gases: Particles are far apart and move freely, filling any container they are in.

Phase Changes

Phase changes occur when matter transitions from one state to another due to changes in temperature or pressure.

• Melting: The process where a solid turns into a liquid when heated. The temperature at which this occurs is the melting point.
• Boiling: The process where a liquid turns into a gas when heated. The temperature at which this occurs is the boiling point.
• Evaporation: A type of vaporization that occurs on the surface of a liquid as it changes into a gas at temperatures below boiling.

Diffusion

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. This process occurs in gases and liquids and is driven by the kinetic energy of particles.

Example: The smell of perfume spreading across a room is due to diffusion.

Brownian Motion

Brownian motion is the random movement of particles suspended in a fluid (liquid or gas) resulting from collisions with fast-moving molecules in the fluid.

Example: Pollen grains moving erratically in water, observed under a microscope, demonstrate Brownian motion.