Conceptual PhysicsConceptual Physics

Notes on Chapter 21-22Notes on Chapter 21-22

Temperature, Heat, Temperature, Heat, Heat TransferHeat Transfer

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

This is going to be a This is going to be a REVIEWREVIEW of last of last years chemistry class.years chemistry class.

However, we are going to look at this from However, we are going to look at this from a a PHYSICS perspectivePHYSICS perspective. .

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

All matter is composed of “jiggling” atoms. All matter is composed of “jiggling” atoms. This matter has This matter has kinetic energy kinetic energy (Ch.8).(Ch.8).

This kinetic energy causes an effect we This kinetic energy causes an effect we call warmth or call warmth or TEMPERATURETEMPERATURE. .

Cold objectsCold objects have Less kinetic energy. have Less kinetic energy. Hot objectsHot objects have More kinetic energy. have More kinetic energy.

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Most objects Most objects expandexpand when it gains energy and when it gains energy and contractscontracts when it losses energy. A when it losses energy. A

Thermometer is a good exampleThermometer is a good example..

Celsius ScaleCelsius Scale Fahrenheit ScaleFahrenheit Scale Kelvin ScaleKelvin Scale

Celsius Scale – named in honor of astronomer Andres Celsius (1701 – 1744).Celsius Scale – named in honor of astronomer Andres Celsius (1701 – 1744). Fahrenheit Scale - named in honor of German physicist Gabriel Fahrenheit (1686 – 1736).Fahrenheit Scale - named in honor of German physicist Gabriel Fahrenheit (1686 – 1736). Kelvin Scale - named in honor of British physicist Lord Kelvin (1824 – 1907).Kelvin Scale - named in honor of British physicist Lord Kelvin (1824 – 1907).

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

The energy that transfers from one object to another The energy that transfers from one object to another because of a temperature difference between them is because of a temperature difference between them is called called HEATHEAT..

Note: Matter Note: Matter DOES NOTDOES NOT contain heat. contain heat.• Matter contains Matter contains ENERGYENERGY in the form of heat. in the form of heat.

The grand total of all energies inside a substance is called The grand total of all energies inside a substance is called INTERNAL ENERGYINTERNAL ENERGY..

A substance that does not contain heat, still contains internal A substance that does not contain heat, still contains internal energy (atoms vibrating).energy (atoms vibrating).

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Measurement of HeatMeasurement of Heat

The most common unit of heat The most common unit of heat is the is the CALORIECALORIE. The calorie is . The calorie is defined as the amount of heat defined as the amount of heat required to raise the required to raise the temperature of 1 gram of water temperature of 1 gram of water by 1by 1°C.°C.

IMPORTANT: IMPORTANT: CalorieCalorie and and caloriecalorie are both units of energy. are both units of energy. CalorieCalorie is the Food version. is the Food version.

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Specific Heat CapacitySpecific Heat Capacity

Different objects have Different objects have different capacities for storing different capacities for storing internal energy.internal energy. Aluminum foil cools very Aluminum foil cools very

rapidly…food in container does rapidly…food in container does not!not!

We call this We call this Specific heat capacitySpecific heat capacity..

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

ApplicationsApplications This leads to increased “jiggle” of atoms which tend This leads to increased “jiggle” of atoms which tend

to move apart. The result is to move apart. The result is EXPANSION EXPANSION of the of the substance.substance.

Bimetallic strip … ThermostatBimetallic strip … Thermostat

Bridge GapsBridge Gaps

Jar lidsJar lids

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Conduction, Convection, RadiationConduction, Convection, Radiation Conduction Conduction

The direct transfer or movement of warmth and energy from one The direct transfer or movement of warmth and energy from one molecule to another molecule by collision.molecule to another molecule by collision.

Convection Convection The organized motion or movement of large groups of molecules based The organized motion or movement of large groups of molecules based

on their relative densities or temperatures.on their relative densities or temperatures.

Radiation Radiation The method by which the sun's energy reaches the earthThe method by which the sun's energy reaches the earth

Temperature, Heat, Heat TransferTemperature, Heat, Heat TransferNewton’s Law of CoolingNewton’s Law of Cooling

Newton's Law of Cooling states that the rate of Newton's Law of Cooling states that the rate of change of the temperature of an object is change of the temperature of an object is proportional to the difference between its own proportional to the difference between its own temperature and the ambient temperature (i.e. temperature and the ambient temperature (i.e. the temperature of its surroundings). the temperature of its surroundings).

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Global Warming & the Global Warming & the Greenhouse EffectGreenhouse Effect

Earth’s atmosphere is Earth’s atmosphere is transparent to solar transparent to solar energy. This traps the energy. This traps the energy…the energy…the greenhouse effectgreenhouse effect..

Temperature, Heat, Heat TransferTemperature, Heat, Heat Transfer

Global Warming & the Global Warming & the Greenhouse EffectGreenhouse Effect

This is good in that it This is good in that it helps heat the earth. helps heat the earth. HOWEVERHOWEVER…to much …to much

heating leads to heating leads to global global warming.warming.