States of matter study guide

Solid

State of matter with both a fixed (definite) shape and a fixed (definite) volume.

Liquid

State of matter with a fixed (definite) volume but an indefinite (not fixed) shape.

Gas

State of matter with neither a fixed shape nor a fixed volume.

Kinetic Molecular Theory (KMT)

Theory that explains matter's behavior based on particles being in constant, random motion.

Temperature

A measure of the average kinetic energy (energy of motion) of the particles in a substance.

Melting

Phase change: Solid to Liquid. Requires adding heat (Endothermic).

Freezing

Phase change: Liquid to Solid. Requires removing heat (Exothermic).

Vaporization (Boiling/Evaporation)

Phase change: Liquid to Gas. Requires adding heat (Endothermic).

Condensation

Phase change: Gas to Liquid. Requires removing heat (Exothermic).

Sublimation

Phase change: Solid directly to Gas (skips liquid phase). Requires adding heat (Endothermic).

Deposition

Phase change: Gas directly to Solid (skips liquid phase). Requires removing heat (Exothermic).

Endothermic

A process that absorbs (takes in) thermal energy/heat from the surroundings (e.g., melting, boiling).

Exothermic

A process that releases (gives off) thermal energy/heat to the surroundings (e.g., freezing, condensation).

How Adding Heat Works

Heat increases the kinetic energy (speed) of particles, causing them to overcome the attractive forces holding them together, resulting in a change to a less ordered state (Solid -> Liquid -> Gas).

How Removing Heat Works

Heat removal decreases the kinetic energy (speed) of particles, causing them to slow down. This allows the attractive forces between particles to pull them closer, resulting in a change to a more ordered state (Gas -> Liquid -> Solid).

Example: Water at 25°C

Liquid (Indefinite shape, Definite volume)

Example: Ice at -5°C

Solid (Definite shape, Definite volume)

Example: Steam at 105°C

Gas (Indefinite shape, Indefinite volume)

What happens to particles when temperature increases?

They speed up and move farther apart.

What happens to a substance when it is changing phase (e.g., melting)?

Its temperature remains constant.

What is the relationship between the Melting Point and Freezing Point?

They are the same temperature.

The general term for a change in the physical form of matter (e.g., solid to liquid).

Phase Change

The change from a solid to a liquid.

Melting

The change from a liquid to a solid.

Freezing

The change from a liquid to a gas.

Vaporization

The change from a gas to a liquid.

Condensation

The change from a solid directly to a gas.

Sublimation

The change from a gas directly to a solid.

Deposition