HEAT Miller. Introduction: Temperature = a measure of the AVERAGE kinetic energy in a substance....

HEATHEATMiller

Introduction:Introduction:Temperature = a measure of

the AVERAGE kinetic energy in a substance.

Heat energy is measure in Joules

ExpansionExpansionDef: When objects are heated up

and their temperature increases, they will normally expand .◦The molecules move farther apart.

ContractionContractionDef: When objects cool down

they will normally contract. ◦The molecules come closer together.

Absolute Zero:Absolute Zero:0K or -273 ˚C

◦All molecular motion stops◦Is only a theory◦The basis for the Kelvin scale

Temperature Scales:Temperature Scales:Kelvin

◦0 K is the lowest temp possible This is absolute zero

Fahrenheit ◦Freezing point of water 32◦ F, and the

boiling point is 212◦F.Celsius

◦Freezing point of water is 0◦C, and the boiling point is 100◦C.

◦Scientists use the Celsius scale

Converting Fahrenheit to Converting Fahrenheit to CelsiusCelsiusTo convert temp from ◦F to ◦C:◦C= (5/9) (◦F-32)

To convert temp from ◦C to ◦F: ◦F= (9/5) (◦C ) + 32

To convert temp from ◦C to K:K = ◦C + 273

Example:Example:To convert 68 ◦F to ◦C, first subtract

32 , multiply by 5 and then divide by 9. The result is 20 ◦C.

*Remember: ◦C= (5/9) (◦F-32)

◦C= (5/9) (68◦F-32)

◦C= (5/9) (36)◦C=180/9◦C= 20

Heat:Heat:Def: The transfer of energy

between objects that are at different temperatures;

Energy is always transferred from higher-temperature to lower-temperature objects, until thermal equilibrium is reached.

3 Types of Heat Transfer:3 Types of Heat Transfer:

Conduction

Convection

Radiation

Heat Transfer #1:Heat Transfer #1:

Conduction = transfer of heat by direct contact (molecule to molecule)◦Ex- metal spoon in a hot bowl of soup

◦Conductors- conduct thermal energy very well Ex- Iron, steel, gold

◦Insulators- Do NOT conduct thermal energy well Ex – rubber, plastic, wood

Examples:Examples:Conductor(metal)

Insulator (rubber)

Heat Transfer #2:Heat Transfer #2:Convection = Transfer of

energy by convection currents in liquids

and gasesWarmer fluids are less dense

than colder fluids, thus warm fluids rise and cold fluids fall.◦ fluid = anything that flows (liquids & gases)◦ not possible in solids◦ hot air balloons, “convection” ovens

Example:Example:The water at the bottom of a pot on

a stove burner gets hot because of contact with the pot itself (conduction).

As a result, the hot water becomes less dense because its higher-energy particles have spread apart.

As the warm molecules rise to the top of the pot the cooler molecules sink back down into the pot.

This circular motion creates a convection current.

Heat Transfer #3:Heat Transfer #3:

Example:Example:The coils of an open heater warm

a room by radiating visible light and infrared waves.

Thermal Energy:Thermal Energy:Def: The total energy is equal to

the particles that make up a substance.

An object at a high temperature has more thermal energy than the same object at a lower temperature.

The more moving particles that you have, the greater the thermal energy!!

Example:Example:When you hold an ice cube in

your hand, thermal energy is transferred from your hand to the ice cube.

The ice cube’s thermal energy will increase and your hand’s thermal energy will decrease!!◦THIS MAKES YOUR HANDS FEEL

COLD!!

Thermal Conductivity:Thermal Conductivity:Def:

The amount of energy at which a substance conducts thermal energy.

Specific Heat Capacity:Specific Heat Capacity:Def: The amount of energy

needed to change the temperature of a 1kg object by 1˚C.

The law of conservation of The law of conservation of energy:energy:States that; energy cannot be

created or destroyed.

Review:Review:What are the 3 types of

temperature scales?

Kelvin, Fahrenheit, and Celsius

Review:Review:List the three types of thermal

energy transfer and give an example of each.

Conduction- molecules have to be touching!!

Convection- thermal heat currents

Radiation- travels is waves

Review:Review:What is the difference between

heat and temperature?

Temperature = a measure of the AVERAGE kinetic energy in a substance.

Heat=The transfer of energy between objects that are at different temperatures.

Review:Review:What is absolute zero?

0K or -273 ˚C◦All molecular motion stops◦Is only a theory◦The basis for the Kelvin scale

Review:Review:If it is 62 ◦F outside today, what would

the temperature be in ◦C?◦16.66 ◦C

What would it be in K?◦289.66 K