Thermal Energy

Milbank High School

Sec. 12.1Temperature and Thermal

Energy

• Objectives– Describe the nature of thermal energy– Define temperature and distinguish it from

thermal energy– Use the Celsius and Kelvin temperature

scales and convert one to the other– Define specific heat and calculate heat

transfer

Thermodynamics

• “The study of heat”

• Kinetic-molecular theory

• Thermal Energy– Overall energy of motion of the particles

that make up an object

• Temperature

Equilibrium/Thermometry

• Conduction

• Thermal Equilibrium

• Thermometer

Celsius and Kelvin

• Celsius– Water freezes at 0°C– Boils at 100°C

• Kelvin– Water freezes at 273 K

• Absolute Zero– -273°C– 0 K

Heat and Thermal Energy

• Heat– The energy that flows between two objects as a

result of a difference in temperature (Q)– Measured in Joules (energy)

• Convection • Radiation• Specific Heat

Q = mCΔT

Calorimetry

• A device used to measure changes in thermal energy

• Insulated• Conservation of Energy in a closed

system• Example Problem

– Heat Transfer in a Calorimeter

Review Concepts…• Temperature is proportional to the average

________________of its particles.• Thermal energy is the measure of ______________.• At absolute zero, ________________.• Can you take the temperature inside of a vacuum?• Which liquid would an ice cube cool faster, water or

methanol?• Why do easily vaporized liquids, such as acetone and

methanol, feel cool to the skin?

Sec. 12.2Change of State and Laws of

Thermodynamics

• Objectives– Define heats of fusion and vaporization– State the first and second laws of thermodynamics– Define heat engine, refrigerator, and heat pump– Define entropy

Change of State

• Melting point• Boiling point• Heat of fusion

Q = mHf

• Heat of vaporization Q = mHv

• Example Problem– Melting a Solid and Warming the Resulting Liquid

The First Law of Thermodynamics

• Thermodynamics

• The total increase in the thermal energy of a system is the sum of the work done on it and the heat added to it

• Heat Engine

RefrigerationRefrigeration-- Cooling by evaporation. Compress & cool to liquefy a gas (outside the fridge) then boil it in a vacuum (inside the fridge) to absorb heat.

The Second Law of Thermodynamics

• Entropy

• Natural processes go in a direction that maintains or increases the total entropy on the universe– Things become more disordered

Review Concepts…

• Can you add thermal energy to an object without increasing its temperature?

• When wax freezes, is energy absorbed or released by the wax?

• You are boiling pasta. Will it cook faster if the water is boiling vigorously or if it is boiling gently?

Review• The second law of thermodynamics states

that natural processes go in a direction that maintains or increases total __________.

• First law of thermodynamics says that _________ + _________=___________

• Heat of fusion• Heat of vaporization• The three types of thermal energy transfer

are _________, _________, and _________.

Review • Entropy!

– How does it relate to creation/evolution?– The entropy of the universe always ___________

(increases or decreases).

• An internal combustion engine converts _________energy to ________ energy.

• _________ ________ is the quantity of heat required to raise the temperature of one kilogram of a substance by one kelvin.

Review• What does the kinetic-molecular theory

state?

• _______________is the study of heat.

• When using a thermometer, energy is transferred via a process called ____________.