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 temperature
Or
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
CONVERSION
TC =
5
(TF
9
- 32°)
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
CONVERSION
TK = TC + 273
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 vs. Heat
• 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
Kelvin
Degrees Celsius
Peak emittance wavelength[65]
of black-body radiation
0K
−273.15 °C
cannot be defined
100 pK
−273.149999999900 °C
29,000 km
450 pK
−273.14999999955 °C
6,400 km
0.001 K
−273.149 °C
273.16 K
0.01 °C
Water's boiling point[A]
373.1339 K
99.9839 °C
Incandescent lamp[B]
2500 K
≈2,200 °C
Sun's visible surface[D][69]
5,778 K
5,505 °C
28 kK
28,000 °C
16 MK
16 million °C
350 MK
350 million °C
2 GK
2 billion °C
3 GK
3 billion °C
350 GK
350 billion °C
1 TK
1 trillion °C
10 TK
10 trillion °C
1.417×1032 K
1.417×1032 °C
Absolute zero
(precisely by definition)
Coldest temperature
achieved[66]
Coldest Bose–Einstein
condensate[67]
One millikelvin
(precisely by definition)
Water's triple point
(precisely by definition)
Lightning bolt's
channel[E]
Sun's core[E]
Thermonuclear weapon
(peak temperature)[E][70]
Sandia National Labs'
Z machine[E][71]
Core of a high-mass
star on its last day[E][72]
Merging binary neutron
star system[E][73]
Relativistic Heavy
Ion Collider[E][74]
CERN's proton vs
nucleus collisions[E][75]
Universe 5.391×10−44 s
after the Big Bang[E]
2.89777 m
(radio, FM band)[68]
10,608.3 nm
(long wavelength I.R.)
7,766.03 nm
(mid wavelength I.R.)
1,160 nm
(near infrared)[C]
501.5 nm
(green-blue light)
100 nm
(far ultraviolet light)
0.18 nm (X-rays)
8.3×10−3 nm
(gamma rays)
1.4×10−3 nm
(gamma rays)[F]
1×10−3 nm
(gamma rays)
8×10−6 nm
(gamma rays)
3×10−6 nm
(gamma rays)
3×10−7 nm
(gamma rays)
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 (32freezing 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 Scales
Celsius and Fahrenheit
oC
= 5/9(oF – 32)
oF=
9/5o + 32
Converting Between Scales
Celsius and Kelvin
K= oC + 273
Practice
• Convert 32oF into Celsius (Proof of Concept)
Practice
• Convert 32oC into K
Practice
• Convert 580oF into K