Ch. 13 - Energy II. Thermal Energy Temperature Thermal Energy Heat Transfer.

Ch. 13 - EnergyCh. 13 - Energy

II. Thermal Energy Temperature Thermal Energy Heat Transfer

A. TemperatureA. Temperature

Temperature A measure of the

average kinetic energy of an object’s atoms or molecules

A measure of how hot (or cold) something is.

Temperature & KETemperature & KEThe higher the temperature the

more kinetic energy the particles in the substance have.

The lower the temperature the less kinetic energy the particles in the substance will have.

B. Thermal EnergyB. Thermal EnergyThermal Energy

the sum of the kinetic and potential energy of all the atoms in an object

Thermal energy increases as temperature increases

At constant temperature, thermal energy increases if mass increases.

B. Thermal EnergyB. Thermal EnergyWhich beaker of water has more

thermal energy? B - same temperature, more mass

200 mL

80ºC

A400 mL

80ºC

B

C. Heat TransferC. Heat TransferHeat- the energy transfer

between objects that are at different temperatures.

Energy is always transferred from higher temperature objects to cooler temperature objects.

C. Heat TransferC. Heat TransferWhy does A feel hot and B feel cold?

80ºC

A10ºC

B

Heat flows from A to your hand = hot. Heat flows from your hand to B = cold.

Heat TransferHeat TransferTransformations of energy usually

produce heat!In all Energy transfers, the energy is

spread out uniformly.There are 3 types of energy transfers:

1. Conduction2. Convection3. Radiation

Heat TransferHeat Transfer1. Conduction

The movement of heat through material.

The heat energy is passed from molecule to molecule

Conduction requires direct contact in order for heat to transfer.

Conduction Example: When you grab the handle of a

hot pan on the stove, conduction transfers some of the heat in the pan to your hand resulting in a pain or burn.

Heat TransferHeat Transfer

2. Convection The transfer of

thermal energy by the fluid (gas or liquid) of heated matter particles• Convection

currents transfer heat from warmer to cooler parts of a fluid

Convection Example:A convection oven utilizes a fan to

better move the heated air around the food so that it cooks faster.

Heat Transfer Heat Transfer 3. Radiation

energy transfer by electromagnetic waves

Electromagnetic waves do NOT require a medium in order to travel, therefore, solar radiation can travel through outer space to warm the earth!

Radiant energy can be absorbed, reflected, or transmitted depending upon the properties of the material receiving the energy.

Some forms of radiation (radiant energy) can pass through solids, liquids and gases.

All objects give off radiant energy! Yes, even us!

D. Conductors and InsulatorsD. Conductors and InsulatorsConductor – any material through

which energy can be easily transferred as heat Examples – metals (copper)

Insulator – any material through which energy cannot be easily transferred as heat – a poor conductor

Let’s review…Let’s review…

https://www.youtube.com/watch?feature=player_detailpage&v=7Y3mfAGVn1c