Temperature:Fahrenheit, Celsius, and Kelvin

Temperature vs. Heat

With your neighbor, try to distinguish between temperature and heat.

(Qualitatively and Quantitatively)

Thermal Energy (Heat) & Temperature

• How would you describe the temperature of a steaming cup of coffee?

• If you said it is “hot” do you mean: A) It has high temperatureOr B) It has a large amount of thermal energy?

• Let’s think about Temperature and Thermal Energy and see if there is a difference.

Temperature

• Operational Definition: Defined in terms of how a property is measured.

-Thermometers have a liquid that when placed in contact with another body either expands or contracts.

-To be useful, a thermometer needs a scale with major and minor delineations

Celsius

• 1742 Swedish astronomer, Anders Celsius used a mercury thermometer and defined his scale in terms of critical points of pure water.

Advantages:-Reproducible-Scale of 10

Disadvantages:-Arbitrary zero value-Negative numbers

TC (TF - 32°)CONVERSION

Kelvin

• 1848, British scientist, William Thomson Lord Kelvin developed a scale that relies on the average kinetic energy of atoms.

Advantages:-Absolute scale-Empirical-No Negatives-Still a scale of 10

TK = TC + 273CONVERSION

Temperature

• Roughly speaking, temperature is a comparative measure of hot and cold

• Kelvin is based on measuring the average kinetic energy of atoms in a sample…

Thermal Energy

• The sum of the kinetic and potential energies of the atoms/molecules in a body. Thermal Energy is also referred to as INTERNAL Energy.

• Temperature in the basic sense, is a measurement of hot and cold.

• Specifically, temperature gives us a measure of the average kinetic energy of particles in a sample

• Heat represents the total kinetic energy of particles in a sample

Temperature vs. Heat

Temperature

Peak emittance wavelength[65]

of black-body radiationKelvin Degrees Celsius

Absolute zero(precisely by definition) 0 K −273.15 °C cannot be defined

Coldest temperatureachieved[66] 100 pK −273.149999999900 °C 29,000 km

Coldest Bose–Einsteincondensate[67] 450 pK −273.14999999955 °C 6,400 km

One millikelvin(precisely by definition) 0.001 K −273.149 °C 2.89777 m

(radio, FM band)[68]

Water's triple point(precisely by definition) 273.16 K 0.01 °C 10,608.3 nm

(long wavelength I.R.)

Water's boiling point[A] 373.1339 K 99.9839 °C 7,766.03 nm(mid wavelength I.R.)

Incandescent lamp[B] 2500 K ≈2,200 °C 1,160 nm(near infrared)[C]

Sun's visible surface[D][69] 5,778 K 5,505 °C 501.5 nm(green-blue light)

Lightning bolt'schannel[E] 28 kK 28,000 °C 100 nm

(far ultraviolet light)Sun's core[E] 16 MK 16 million °C 0.18 nm (X-rays)

Thermonuclear weapon(peak temperature)[E][70] 350 MK 350 million °C 8.3×10−3 nm

(gamma rays)

Sandia National Labs'Z machine[E][71] 2 GK 2 billion °C 1.4×10−3 nm

(gamma rays)[F]

Core of a high-massstar on its last day[E][72] 3 GK 3 billion °C 1×10−3 nm

(gamma rays)Merging binary neutronstar system[E][73] 350 GK 350 billion °C 8×10−6 nm

(gamma rays)

Relativistic HeavyIon Collider[E][74] 1 TK 1 trillion °C 3×10−6 nm(gamma rays)

CERN's proton vsnucleus collisions[E][75] 10 TK 10 trillion °C 3×10−7 nm

(gamma rays)Universe 5.391×10−44 safter the Big Bang[E] 1.417×1032 K 1.417×1032 °C 1.616×10−27 nm

(Planck Length)[76]

Physical Properties that Depend on Temperature

Temperature Scales

• Fahrenheit (oF)*Introduced in 1724*Defined by 2 fixed points based on the properties of water (32-

freezing pt/212-boiling point)*First modern thermometer (Hg)

• Celsius (oC)*Introduced 18 years later (1742)

*Defined by setting boiling point of water to 0o and boiling point to 100o

*Absolute zero in Celsius is -273.15o

• Kelvin*Introduced 1848*Zero point set to Absolute Zero

Converting Between ScalesCelsius and Fahrenheit

oC = 5/9(oF – 32)

oF= 9/5o + 32

K= oC + 273

Converting Between ScalesCelsius and Kelvin

Practice

• Convert 32oF into Celsius (Proof of Concept)

Practice

• Convert 32oC into K

Practice

• Convert 580oF into K