Phase Change and Thermodynamics

Absolute Zero

The temperature at which a substance has no kinetic energy per particle (thermal) to give up. This temperature corresponds to 0K or to -273 degrees C.

Boiling

The change of phase from liquid to gas that occurs beneath the surface in the liquid. The gas forms bubbles that rise to the surface and escape.

Boiling Point

The temperature at which the pressure of the vapor of a liquid is equal to the external pressure acting on the surface of the liquid.

Condensation

The change of phase of a gas into a liquid; the opposite of evaporation.

Entropy

A measure of the amount of disorder in a system.

Evaporation

The change of phase from liquid to gas that takes place at the surface of a liquid.

First Law of Thermodynamics

States that if the mechanical energy of a system is constant, the increase in the thermal energy of the system equals the sum of the thermal energy transferred into the system and the work done on the system.

Freezing

Change in phase from liquid to solid.

Heat Engine

A device that converts some thermal energy into mechanical energy.

Heat of Fusion

The amount of energy required to change a substance from the solid phase to the liquid phase.

Heat of Vaporization

The amount of energy required for a liquid at its boiling point to become a gas.

Internal Combustion Engine

A heat engine that burns fuel inside the engine in changes or cylinders.

Kinetic Theory

An explanation of the behavior of particles in gases; states that matter is made of constantly moving particles that collide without losing energy.

Melting Point

The temperature at which a solid begins to liquefy.

Phases

One of the four possible forms of matter: solid, liquid, gas, and plasma. Often called state.

Plasma

Matter with enough energy to overcome the attractive forces within its atoms, composed of positively and negatively charged particles.

Pressure

The amount of force exerted per unit area; SI unit is the pascal (Pa).

Regelation

The phenomenon of ice melting under pressure and freezing again when the pressure is reduced.

Saturated

Term applied to a substance, such as air, that contains the maximum amount of another substance, such as water vapor, at a given temperature and pressure.

Second Law of Thermodynamics

States that energy spontaneously spreads from regions of higher concentration to regions of lower concentration.

Sublimation

The process of a solid changing directly to a vapor without forming a liquid.

Thermal Expansion

An increase in the volume of a substance when the temperature is increased.

Thermodynamics

The study of the relationship between thermal energy, heat, and work.

Third Law of Thermodynamics

No system can reach absolute zero.