Temperature Definition and 1000 Threads

Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder or hotter.
Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have used various reference points and thermometric substances for definition. The most common scales are the Celsius scale (formerly called centigrade, denoted as °C), the Fahrenheit scale (denoted as °F), and the Kelvin scale (denoted as K), the last of which is predominantly used for scientific purposes by conventions of the International System of Units (SI).
The lowest theoretical temperature is absolute zero, at which no more thermal energy can be extracted from a body. Experimentally, it can only be approached very closely (100 pK), but not reached, which is recognized in the third law of thermodynamics.
Temperature is important in all fields of natural science, including physics, chemistry, Earth science, astronomy, medicine, biology, ecology, material science, metallurgy, mechanical engineering and geography as well as most aspects of daily life.

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  1. M

    Radiation - temperature - frequency

    Hi. Dunno if this makes much sense. If radiation is emitted from a star with a certain frequency, does that frequency change, if that radiation travels through areas of different temperatures?
  2. T

    Does internal potential energy affects temperature?

    Hello If I take an extreme case, where a body has only an internal potential energy with zero internal kinetic energy, does this body have a temperature? Another question related to it: if two objects A and B having different temperature: A: having only internal potential energy and B having...
  3. JJD

    Rubber stiffness as a function of temperature?

    I'm aware of the concept of rubber as an entropic spring and how increasing the temperature increases the modulus/stiffness of the rubber. I've seen the experiment of how heating a strip of rubber supporting a load will cause it to shorten. But also a rubber will transition from its glass-like...
  4. O

    Do sound waves increase temperature?

    Do sound waves increase the temperature of the medium they are traveling through?
  5. N

    Diffusion across surface with constant temperature

    Homework Statement A Ti Rod is to be put into a furnace to try and increase the carbon content of the rod. Initially, the carbon content of the rod is 0.2%wt. The carbon content of the furnace is 1.0%wt. What would the temperature have to be in order to get a final carbon content in the Ti rod...
  6. J

    Ideal gas temperature proportional to absolute temperature

    Homework Statement I[/B] have some difficulties proving that the ideal gas temperature is directly proportional to absolute temperature defined by the second law of thermodynamics. Homework Equations The ideal gas temp. is defined by the ideal gas equation: pV=NkTi(T), where k is Boltzmann's...
  7. Titan97

    Thermodynamics problem involving piston and spring

    Homework Statement [/B] Homework Equations $$W=P\Delta V$$ $$\Delta U=nC_v\Delta T$$ The Attempt at a Solution . [/B] The gas is slowly heated. The temperature increases and the pressure increases as well. But since volume increases, the increases in pressure is nullified. The process is...
  8. domainwhale

    Insights High Temperature Low Temperature Duality for the Ising Model on an Infinite Regular Tree - Comments

    domainwhale submitted a new PF Insights post High Temperature Low Temperature Duality for the Ising Model on an Infinite Regular Tree Continue reading the Original PF Insights Post.
  9. R

    Temperature for "melting" vibrational degrees of freedom

    Hello everyone! I recently read some information about the equipartition theorem and degrees of freedom in thermodinamics. I read that for the linear N-atomic and non-linear N-atomic molecules in order to allow the vibrational degrees of freedom to appear we need a really high temperature. I...
  10. G

    B Create Black Hole Through Heat or Fusion?

    Would it be possible that you could create a black hole from heating something really hot. I heard Vsauce said if you heat something hot enough that it's wave length of the light released is smaller than the plank length, it would become a black hole. That means that the energy would be on the...
  11. K

    How is internal energy U(S,V) a function of temperature?

    In my chemical thermodynamics class/notes (and other references I've used) it is stated throughout that internal energy U is a function of entropy and volume , i.e. it's "natural" variables are S and V: U = U(S,V) I suspect that I must take this "axiomatically" and move on. Since U is a state...
  12. L

    Temperature Dependence of Donor Ionization Energies

    Donor ionization energies are calculated via the hydrogen-like model and use the static dielectric constant and effective mass to modify the screening between the electron and the donor. Nice and simple, I get it. But in a material the ionized electron needs to go someplace - presumably the...
  13. L

    Need ideas for high temperature sealed container.

    For my bachelor project, I am in need of an air tight (or very, very near air tight) container, which can withstand 750 C. My original thought was to have a steel container with a lid and gasket, but I was unable to find any gaskets that got anywhere near that. Does anyone know of a gasket...
  14. S

    Adiabatic Expansion Pressure Temperature Relation

    Homework Statement The problem is in the context of convection in the troposphere Show that when an ideal gas expands adiabatically, the temperature and pressure are related by the differential equation \frac{dT}{dP} = \frac{2}{f+2} \frac{T}{P} Homework Equations Ideal gas law PV = nRT...
  15. randini

    High temperature insulating material for new engine concept

    In the past, reciprocating engine platforms have prevented the use of thermal insulating materials like ceramics due to, among other reasons, abrasion and vibration. One of the problems in the past has been the movement of the piston and piston rings over the cylinder wall where the insulating...
  16. Abtinnn

    Is temperature directly linked to movement?

    Hey guys, I have been wondering about this for a long time, and I can't seem to reach a solid conclusion. If temperature of an object is related to the movement of its atoms, then is it true to say that a moving object have a higher temperature?
  17. A

    Liquid refrigerant pressure and temperature

    Consider a sealed can of liquid refrigerant-134a in a room at 25 •C .Now if the lid is opened slowly and some refrigerant is allowed to escape, the pressure and temperature in the can start dropping rapidly.A thermometer inserted in the can will register -26°C when pressure drop to 1 atm. ,which...
  18. Titan97

    Find the change in temperature during adiabatic compression

    Homework Statement Homework Equations $$PV^{\gamma}=\mathrm{constant}$$ The Attempt at a Solution Initially, the piston will get a velocity ##v##. But the chamber will move too because of the forces exerted by the gas. Since total external force is zero, velocity of centre of mass is...
  19. JoAstro

    What Is the Effective Temperature and Luminosity of Star A?

    I am trying to find the temperature of a star given its wavelength in micrometres, but I am not sure if my conversion is right therefore don't know if the answer is correct. Star A has a maximum emission wavelength of 1 μm and Radius 100 Rsun. What is its Effective Temperature and Luminosity...
  20. Absentee

    Wet-Bulb Temperature: Exploring the Science Behind Evaporative Cooling

    Homework Statement Imagine a wet thermometer whose bulb is covered with a wet wick at 1 atm. Temperature of the water happens to drop during the process of evaporation. Homework Equations N/A The Attempt at a Solution Does evaporation lower the temperature of water just by removing...
  21. A

    Could Turbine Exhaust Temperatures Reach Below Zero Celsius?

    Could turbine exhaust temperature be negative Celcius? My calculations yield 176 K. Is that possible? Inlet conditions are 7.8 MPa and 625 K. Exit pressure is 1 atm. (100 kPa.)
  22. Ioana Gherghel

    Water temperature calculation of glass facade

    Hello everybody I am an architecture student working on a facade system and because I do not have much physics knowledge I stumbled across a question I can't answer myself: If my facade is actually a thin parallelipiped glass tank filled with water, how do I measure the temperature changes of...
  23. Ryaners

    Calculating entropy change associated with change in temperature

    Hi folks, This is a question about how to calculate entropy change when there is a temperature change involved. I got the correct answer to this, but I don't actually understand why it's correct..! Any help is much appreciated. Homework Statement One mole of liquid bromine is heated from 30...
  24. Jhon Paul

    Transmittance of Cyclohexane for IR Radiation Through Quartz Viewport

    I am interested to use a pyrometer to measure the temperature of a graphite heater while it is being heated (upto 1200 degC). The heater is located inside a small chamber filled with liquid cyclohexane . For viewing purpose of the pyrometer the chamber is having a viewport of Quartz. The...
  25. Y

    Does Data in Informatics TRULY Have Temperature?

    http://arxiv.org/ftp/cs/papers/0701/0701016.pdf The above is link of Kafri's paper I was just studying at high school when I found this theoretical scientific discovery proposed by an enough notable Israeli physicist Oded Kafri. He made a unique unification or link between second law of...
  26. sandrogiongo

    Why is there no continuity on the temperature of the CMB?

    On the epoch of last scattering, the universe became transparent and the typical CMB photon was "free" to travel the universe. The corresponding radiation was of a black body temperature of ~3000K. My question is: after the last scattering, the universe was still hot and, I presume, emitting...
  27. J

    Using Peltier Plates for heating

    I know that peltier plates are for cooling(mostly :smile:) but I wish to try out heating other substances using peltier plates. I'm planning to use 3 peltier plates (TEC1-12712) [maximum temperature difference of 70 degrees measured at 25 degrees / Maximum temperature difference of 80 degrees...
  28. ChloeYip

    Temperature in Vacuum: Is it Zero or Undefined?

    I have learned that temperature is defined as the vibration of particles. However, in vacuum, there is no particles. In reality, no absolute vacuum can be done, so I can't find answer online. Do you think the temperature (in Kelvin) is zero or undefined? Thank you.
  29. mrspeedybob

    Temperature cycling effects on electronics durability

    I just went out to my car to retrieve my laptop. My car is at about 1 degree C, my house is at about 20 degrees C. I soon noticed condensation forming on the screen and it occurred to me that condensation was probably forming inside as well on the electrical components. The combination of...
  30. terryds

    On what does temperature depend ?

    Does temperature depend on the kinetic energy, or internal energy ?? Does it only depend on the movement of the molecules, or also the potential energy of molecules??
  31. K

    What is the new temperature of the system?

    Homework Statement A liquid is enclosed in a metal cylinder that is provided with a piston of the same metal. The system is originally at a pressure of 1.00 atm (1.013 x 105 Pa) and at a temperature of 30 °C. The piston is forced down until the pressure on the liquid is increased by 50.0 atm...
  32. B

    What Are the Standard Enthalpy and Entropy Changes for the Graphed Reaction?

    Homework Statement My questions are based on a graph. I am trying to figure out the standard ΔH change for the graphed reaction and the standard entropy change. (1) What is the standard enthalpy change for the graphed reaction? (A) -31 KJ/mol (B) 0 (C) +12 KJ/mol (D) +11 KJ/mol (2) What is...
  33. N

    Calculating Fire Temperature from Thermal Energy

    is there a way to calculate the themperture of something like a fire, if you know the thermal energy it produces.
  34. T

    GISS surface temperature - confidence intervals

    The HadCRUT4 global surface temperature anomalies in tabular form include confidence intervals. The GISS surface temperature data is available in tabular text form here http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt - but it doesn't include any confidence intervals. Can...
  35. T

    Finding current and temperature of platinum wire

    I plan on using a 1 ft long, 0.005" diameter platinum wire as part of an electrode. The wire will be bare but will be inside a hollow plastic tube that has an inner diameter of 0.08". It needs to be able to carry a maximum of 1 mA for a length of 10 minutes, while not exceeding 60oC. I'm not...
  36. T

    What effect would one expect if the Critical Temperature is

    The measurement of electrical resistance as a function of the superconductor's temperature yields fundamental insights into its properties. The Critical Temperature, Critical Current Density, and the Critical Magnetic Field, can all be obtained through variations of a basic experiment. I would...
  37. M

    Why Is My Calculated Debye Temperature for Sodium Higher Than Literature Values?

    Homework Statement Na has a bcc structure with molecular mass of 22.99 gr/mol, mass density of 0.971 gr/cm^3. The average speed of sound in Na (at room temperature=300K) is 3200 m/s. Calculate the Debye temperature for Na Homework Equations I worked out this equation to calculate the Debye...
  38. K

    What is the change in entropy ΔS of the gas?

    Homework Statement Two moles of an ideal gas undergo a reversible isothermal expansion from 3.37×10−2m3 to 4.29×10−2m3 at a temperature of 29.6 ∘C. What is the change in entropy ΔS of the gas? Homework Equations pV=nRT The Attempt at a Solution W=∫V2V1pdV, I don't know how to use this...
  39. F

    Why does the temperature is invariant on phase transitions?

    Hello there, this is a fact that I can't understand thinking about it... Energy has to be given so that the inter molecular bonds can be broken, and energy goes in when there are formed (even though that sounds very counter intuitive to me), but why is the energy all distributed to potential...
  40. K

    Thermodynamics, saturated Pressure and temperature

    I wonder why we can find temperature (or pressure )when the other property value is given.Lets say we have a rigid tank, which contains 50Kg of water at 90 degree celsius. If we look up the thermodynamics table, we can find the saturation pressure 70.14 kpa and definite liquid and gas specific...
  41. David Gin

    Automated Chiller Temperature Control System

    Hi All, I'm working on an automated chiller control system for final year project. It is a logic control that automatically set the chill water supply temperature based on current demand load and the chillers performance curve to achieve the best efficiency COP for the system. For a variable...
  42. M

    What is the relationship between heat capacity and temperature?

    Hello, I'm reposting this 'cause I think it's more relevant here than where it was posted before. Not sure how to delete the other one... I'm trying to plot the heat capacity as a function of the temperature from some small temperature to Debye's using numerical summation over the energy (shown...
  43. L

    Temperature & Wind Chill: Why Does It Feel Colder?

    Hi all, so when you heat something up the molecules begin to move faster. This is seen when you steam a tea kettle. So my question is when its very cold outside and there is no wind, it is much more comfortable then when there is cold wind whipping about your body. If molecules moving faster are...
  44. T

    Why is the transition in resistance gradual at the Critical Temperature

    Hello. The measurement of electrical resistance as a function of the superconductor's temperature yields fundamental insights into its properties. The Critical Temperature, Critical Current Density, and the Critical Magnetic Field, can all be obtained through variations of a basic experiment. I...
  45. T

    Phase changes, change of entropy is temperature independent

    Good morning everyone! My chemistry final is approaching and I have a few difficulties in the thermodynamics chapter. One of the things that are bothering me is the calculation of the temperature of phase change. We know that if a mole of ice at 273K melts, the entropy change would be...
  46. AotrsCommander

    Greenhouse effect on planetary equilibrium temperature help

    I am trying to back-calculate the greenhouse effect on planetary equilibrium temperature for Earth (in the hope I can then attempt applying it to other calculations.) I know that the actual equilibrium temperature of Earth is 287.89K, +33K above the calculated equilibrium temperature: Teq = (Q...
  47. rpthomps

    Calculating Core Temperature of a Brown Dwarf

    To begin with, I am an enthusiastic but very amateur physicist. I am working on my knowledge by taking online open courseware, buying textbooks and doing all the questions. I recently bought Astrophysics of Planet Formation which is no doubt out of my league but I like to pick at it from time to...
  48. B

    Temperature of ideal gas in a cylinder

    Qn : https://www.dropbox.com/s/dpcws9q4bjpzvtp/20151123_112037.jpg?dl=0 Why is option A and C wrong or correct? My attempted answer : A :A is plausible as if the piston is suddenly moved inwards, the gas molecules bounce off the piston at higher speeds Since Temp proportional to rms speed...
  49. Msilva

    Final temperature of a gas passed through a porous plug

    Homework Statement A gas has the following equations of state: P=\frac{U}{V} \,\,\,and \,\,\,T=3B\frac{U^{\frac{2}{3}}}{N^\frac{1}{3}V^\frac{1}{3}} where B is a positive constant. The system obeys the Nernst Postulate (S tends to zero as T tends to zero). The gas, at a initial temperature T_i...
  50. Buzz Bloom

    Question about time and/or temperature of GUT symmetry breaking

    I understand there are quite a few GUT candidates. I also understand that among these candidates some are considered by the theoretical physics community to be more likely to be correct than others. I am curious about what each of the various GUT candidates predicts as the time (relative to...
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