Latent Heat Chapter

Physics Unit 3

Kinetic Theory Postulate 1

Gases are made of many molecules that are in constant, random motion and are separated by large distances relative to their size.

Kinetic Theory Postulate 2

Collisions between gas molecules or with container walls are perfectly elastic—no energy is lost.

Kinetic Theory Postulate 3

Gas molecules move in straight lines unless disturbed by a collision and follow Newton’s laws of motion.

Kinetic Theory Postulate 4

The volume of individual gas molecules is negligible compared to the total volume of the gas.

Kinetic Theory Postulate 5

The average kinetic energy of gas molecules is directly proportional to the absolute temperature.

Calorimeter

To measure the heat of chemical reactions, physical changes, or specific heat capacity.

Latent Heat

The energy absorbed or released during a substance's phase change at constant temperature.

Formula for latent heat

Q = mL, where Q = heat, m = mass, and L = specific latent heat.

Specific heat capacity.

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

Principle of Mixtures

It equates heat lost by a hotter object to heat gained by a cooler one to find unknown specific heat.

3 forms of Heat Transfer

Conduction, Convection, Radiation

Conduction

Heat transfer through direct contact where particles vibrate in place; mainly in solids.

Convection

Heat transfer through fluid movement, where warmer, less dense regions rise and cooler, denser regions sink.

Radiation

Transfer of heat via electromagnetic waves, even through a vacuum.

Example of Conduction

A metal spoon heating up in a cup of hot tea.

Example of convection

Water circulating in a pot while boiling.

Example of radiation

Feeling the warmth from sunlight or a fire without touching it.

Latent heat of fusion

The heat energy required to change a substance from solid to liquid (or vice versa) at its melting/freezing point without changing temperature.

Example of latent heat of fusion.

Melting ice into water or freezing water into ice at 0°C.

Latent Heat of Vaporization

The heat energy required to change a substance from liquid to gas (or vice versa) at its boiling/condensation point without changing temperature.

Example of latent heat of vaporization.

Boiling water into steam or condensing steam into water at 100°C.

Boiling

A rapid vaporization process that occurs throughout the liquid at a fixed temperature called the boiling point.

Evaporation

A slow vaporization process that occurs only at the surface of a liquid and at any temperature below the boiling point.

Heat

Total internal energy of all molecules in an object