ThermodynamicsUnit 6

TemperatureTemperature – A measure of the average

kinetic energy of the particles in an object (how hot or cold).There are three common temperature scales:

Fahrenheit (water freezes at 32° and boils at 212°). Celsius (water freezes at 0° and boils at 100°). Kelvin (water freezes at 273° and boils at 373°).

Thermometer – A device used to measure temperature.

Thermal Equilibrium – When no energy flows from one object to another that are in contact with each other.

Kinetic TheoryThe Kinetic Molecular Theory of Matter

is a concept that basically states that:

ATOMS and MOLECULES

possess an energy of motion (kinetic energy)

that we perceive as temperature.

Kinetic TheoryIn other words

ATOMS and MOLECULES

are constantly in motion

and we measure the energy of these movements

as the temperature of that substance.

Kinetic Theory

This means

if there is an increase in temperature

the atoms and molecules

will gain more energy (kinetic energy)

and move even faster.

Heat TransferHeat – The energy that is transferred from

one body to another because of a difference in temperature.Heat is not a property of an object.Example:The iron is hot, so it's reasonable to say it must

have a lot of heat in it. Reasonable, but wrong. It's more appropriate to say that it has a lot of energy in it (i.e. it has a high temperature), and touching it will cause that energy to transfer to your hand ... in the form of heat.

Heat TransferHeat continued:Heat always flows from high temperature to

low temperature.The SI unit of heat is the joule ( J ).

Types of Heat Transfer:Conduction – Energy transfer from particle to

particle within a substance, or from one material to another when the two are in direct contact. Requires a medium. Example: A spoon left in a pan of soup on the stove.

Heat Transfer (cont.)Convection – A means of heat transfer by movement

of the heated substance itself, such as currents in a fluid. Requires a medium. Example: Air near the surface of the Earth being heated

by the Sun and rising in the atmosphere.Radiation – Energy transmitted by electromagnetic

waves. Does not require a medium. Example: The heat you feel when you stand in front of a

fireplace.

Conductor – A material through which heat can be transferred easily.

Insulator – A material through which heat is not transferred easily.

The Laws of ThermodynamicsThermodynamics – The study of processes in

which energy is transferred as heat and as work.

The Zeroth Law of Thermodynamics - If body A is in thermal equilibrium with body B and body B is in thermal equilibrium with body C, then body A is in thermal equilibrium with body C.

The First Law of Thermodynamics – The law of conservation of energy. A change in the internal energy of a system is equal to the sum of the heat added to the system and the work done on it.

The Laws of ThermodynamicsThe Second Law of Thermodynamics –

Heat cannot be transferred from a colder to a hotter body within a system.

Entropy – (Physics definitions) The quantitative measure of disorder in a system.

a measure of the amount of energy which is unavailable to do work.