Ch. 18 Phases & Energy

Vocabulary flashcards covering phases, energy forms, phase changes, and heat calculations from the lecture notes.

Phase

A distinct form of matter (solid, liquid, or gas) with characteristic particle arrangement and properties.

Solid

A phase where particles form crystals, vibrate mainly in place, and maintain volume and shape.

Liquid

A phase where particles are close together, can vibrate, rotate, and move past one another while staying near each other.

Gas

A phase with large distances between particles, making it easily compressible due to empty space.

Phase Change

Transition between phases (solid ↔ liquid ↔ gas) that involves absorption or release of energy.

Endothermic

A process that absorbs energy from the surroundings.

Exothermic

A process that releases energy to the surroundings.

Vapor Pressure

The pressure of the gas directly above a liquid as it evaporates; increases with temperature and is lowered by stronger particle attractions.

Boiling Point

Temperature and pressure at which a liquid boils; occurs when vapor pressure equals atmospheric pressure.

Melting (Fusion)

Phase change from solid to liquid; energy is absorbed to overcome attractions.

Freezing (Solidification)

Phase change from liquid to solid; energy is released as attractions form.

Vaporization

Phase change from liquid to gas; energy is absorbed to separate particles.

Sublimation

Phase change from solid directly to gas; energy is absorbed.

Kinetic Energy

Energy of motion; for particles this relates to temperature.

Potential Energy

Stored energy due to particle interactions or chemical bonds; changes during phase changes.

Energy

The ability to do work or transfer heat; cannot be created or destroyed, only transformed.

Heat

Transfer of energy between objects due to a temperature difference; flows from warmer to cooler.

Specific Heat Capacity

The amount of heat required to raise the temperature of 1 g of a substance by 1°C (or 1 K).

q (Heat energy)

The energy transferred as heat during a process; positive for gain, negative for loss; used with msΔT.

ΔT

Final temperature minus initial temperature (Tf − Ti).

Mass (m)

Mass of the substance used in heat calculations (in grams in the examples).

Specific Heat (s)

The amount of heat required to raise 1 g of a substance by 1°C; units J/g°C.

Joule

SI unit of energy.

Kilojoule

1000 joules.

Calorie (cal)

Amount of energy required to raise 1 g of water by 1°C; equal to 4.184 J.

Calorie (Cal) / kcal

Unit used in nutrition; 1 kcal = 1000 cal = 4.184 kJ.

Single Phase

A state where energy can change temperature but the substance does not change phase.

Boiling Point vs Vapor Pressure

Boiling point is reached when vapor pressure equals atmospheric pressure; vapor pressure is the pressure of vapor above a liquid.