States of Matter, Phase Changes, and Diffusion

Kinetic Particle Theory

The theory stating that matter is made up of tiny, indivisible particles that are in constant, random motion.

Solid State (Particle Characteristics)

Particles are arranged in a regular pattern, closely packed together, and vibrate about fixed positions with low energy and high density.

Liquid State (Particle Characteristics)

Particles are randomly arranged, close together (loosely packed), and able to move around or slide over each other with medium density and greater energy than a solid.

Gas State (Particle Characteristics)

Particles are randomly arranged, far apart, and move quickly in all directions with constant random movement, high kinetic energy, and low density.

Endothermic Process

A process or phase change in which thermal energy is absorbed from the surroundings.

Exothermic Process

A process or phase change in which thermal energy is released to the surroundings.

Melting

An endothermic state change from solid to liquid at a specific melting point, where absorbed thermal energy overcomes attractive forces to transition particles from a closely packed regular arrangement to an irregular loosely packed arrangement.

Melting Point

The specific temperature at which a pure substance converts from a solid into a liquid.

Freezing

An exothermic state change from liquid to solid where thermal energy is released, causing attractive forces to strengthen and particles to move from a loosely packed disorderly arrangement into a closely packed regular arrangement.

Boiling

An endothermic state change from liquid to gas occurring throughout the liquid at a single specific temperature called the boiling point.

Evaporation

An endothermic surface phenomenon where high-energy particles at the surface of a liquid escape as a gas at any temperature below the boiling point.

Condensation

An exothermic state change from gas to liquid where particles lose energy, move from very far apart to close (loosely packed), and change from random movement to sliding over each other.

Sublimation

An endothermic state change directly from a solid to a gas without passing through the liquid phase.

Heating Curve Horizontal Plateau

A flat horizontal region on a heating graph indicating a change of state where temperature remains constant because absorbed thermal energy is used to overcome attractive forces between particles rather than increase kinetic energy.

Impurity Effect on Melting Point

Impurities lower the melting point of a pure substance and cause it to melt over a range of temperatures rather than at a sharp, single temperature.

Gas Pressure

The pressure exerted by a gas due to gas molecules colliding with the inner walls of their container.

Effect of Temperature on Gas Volume

Increasing the temperature increases the kinetic energy of gas particles, causing them to move faster and spread out, which increases the volume when pressure is kept constant.

Effect of Temperature on Gas Pressure

Increasing the temperature in a fixed volume increases the kinetic energy of gas particles, causing them to collide more frequently and forcefully with the container walls, increasing pressure.

Effect of Pressure on Gas Volume

Increasing the external pressure at