Temperature v. Heat. Celsius & Kelvin Temperature Scales Boiling point of water Freezing point...

Temperaturev.

Heat

Celsius & Kelvin Temperature Scales

Boiling pointof water

Freezing pointof water

Absolutezero

Celsius

100Celsiusdegrees

100oC

0oC

-273oC

Kelvin

100Kelvins

373 K

273 K

0 K

Temperature is Average Kinetic Energy

Fast Slow“HOT” “COLD”

Kinetic Energy (KE) = ½ m v 2

*Vector = gives direction and magnitude

Temperature Scales

Fahrenheit

212 oF

180 oF

32 oF

Celcius

100 oC

100 oC

0 oC

Kelvin

373 K

100 K

273 K

Boiling point of water

Freezing point of water

Notice that 1 kelvin degree = 1 degree Celcius1 kelvin degree = 1 degree Celcius

Temperature Scales

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 136

Compare Celsius to Fahrenheit

oF – 32 = 1.8 oC

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 139

Temperature Scales

• Temperature can be subjective and so fixed scales had to be introduced.

• The boiling point and freezing point of water are two such points.• Celsius scale (oC)

– The Celsius scale divides the range from freezing to boiling into 100 divisions.

– Original scale had freezing as 100 and boiling as 0.

– Today freezing is 0 oC and boiling is 100 oC.

• Fahrenheit scale (oF)• Mercury and alcohol thermometers rely on thermal expansion

Thermal Expansion

• Most objects e-x-p-a-n-d when heated• Large structures such as bridges must be

built to leave room for thermal expansion• All features expand together

COLDHOT

Cracks in sidewalk.

Equal Masses of Hot and Cold Water

Thin metal wall

Insulated box Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Water Molecules in Hot and Cold Water

Hot water Cold Water90 oC 10 oC

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Water Molecules in the same temperature water

Water(50 oC)

Water(50 oC)

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 291

Heat versus Temperature

Kinetic energy

Fra

ctio

ns o

f pa

rtic

les

lower temperature

higher temperature

TOTALKinetic ENERGY

= Heat= Heat

Temperature vs. Heat

Measuredwith a

Calorimeter

TotalKineticEnergy

Joules(calories)

Measuredwith a

Thermometer

AverageKineticEnergy

oCelcius(or Kelvin)

Alike Different

A Propertyof

Matter

HaveKineticEnergy

Heat

Different

Topic Topic

Temperature

thermometercalorimeter

Conservation of Matter

Reactants yield Products