Thermal Energy

Thermal Energy vs. Temperature• TEMPERATURE: Measure of the AVERAGE kinetic

energy in the particles of a substance.– how fast the particles are moving

• THERMAL ENERGY: Measure of the TOTAL amount of energy in ALL of the particles in an object or substance.– Add the energy of each particle together

Thermal Energy vs. Temperature• Objects with the same thermal energy do NOT

necessarily have the same temperature.– Think of an example…

• Objects with the same temperature do NOT necessarily have the same thermal energy.– Think of an example…

Thermal Energy vs. Temperature• Compare the thermal energy and temperature of

the water in beaker X and beaker Y.

1) Beaker X: 50mL at 22°CBeaker Y: 100mL at 22°C

Beaker X and Beaker Y have the same temperature. Beaker Y has more thermal energy (more molecules).

2) Beaker X: 60mL at 5°CBeaker Y: 60mL at 25°CBeaker Y has more thermal energy because it has a higher temperature (same number of molecules).

Heat• The movement of thermal energy from a

substance with a higher temperature to a substance with a lower temperature.

• 3 types of heat:– Conduction– Convection– Radiation

Conduction

• Energy is transferred by contact between particles– The particles of one substance bump into the particles

of another substance• How did we observe conduction in the Heat Lab?

Convection• Energy is transferred by the

movement of CURRENTS within a fluid (liquid or gas)– Convection Current – The

flow of heat through a fluid. Warmer less-dense fluid rises while cooler more-dense fluid sinks, creating a flow or current

• How did we observe convection in the lab?

Radiation• Energy is transferred through

electromagnetic waves– Ex: heat from sunlight…mainly

infrared waves– Does not require matter to

transfer energy (can transfer heat through “outer space”)

• How did we observe radiation in the lab?

“Heat flows in one direction.”• Heat flows from

WARMER objects to COOLER objects until both have the SAME temperature.– “EQUILIBRIUM”

temperature

“Heat flows in one direction.”• Which direction will heat flow?

• Your pillow and your head– Head Pillow

• Your seat and your body– Body Seat

• Hot food and the room– Food Room

“Heat flows in one direction.”

• If you hold an ice cube in your hand, your hand will feel cold; explain why.– Thermal energy flows from warmer substances

to cooler substances. Your hand is warmer than the ice cube, so energy flows from your hand to the ice. As your hand loses energy, your body perceives this sensation as “cold”.– There is no such thing as “cold”…only an

absence of heat.• Like dark is the absence of light.

“Heat flows in one direction.”

• You place a can of soda in the freezer. You forget about it until the next day, only to discover it has frozen. Explain the transfer of heat in this case.– The soda is warmer than the freezer, so heat

flows out of the soda into the freezer (air/shelf) until the soda and the air reach the same temperature, which is below the freezing point of soda.