What is Temperature: Definition and 1000 Discussions

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. E

    Compression due to temperature rise vs volume reduction

    If I have 2 sealed tanks A and B of 1 cu ft volume that contain air at atmospheric pressure and are at 300 deg K. temp absolute. For tank A I raise the temperature from 300K to 600K and I suppose the pressure will double due to this and would be 14.7 * 2 = 29.4psi absolute For tank B I use a...
  2. T

    Ice in water question - what is final temperature?

    Homework Statement An ice cube melts in a 10oC glass of water (mass of water is 225g). If the ice is allowed to melt completely, what will the final temperature of the water be? (we're told that the mass of ice can be ignored) Ti = 10oC Latent heat of fusion = Lf = 334000 J/kg specific heat...
  3. V

    Neutron star warm matter - temperature?

    In calculations of quantities in Neutron stars with degenerate matter is usual to set temperature zero. If I'm right it means that pressure of this matter is negligible against pressure due to Pauli principle. But what about situation when the matter is in neutron star locally compressed. How...
  4. P

    Estimating power required to get heat exchanger up to temperature

    Hi, I am working on a fuel delivery system with multiple heat exchangers, piping, etc. I am trying to determine how much power I will need to heat up the gas in the system at the inlet so that all of the components of my system will reach the operating temperatures. For example, I am looking at...
  5. vetgirl1990

    Equilibrium temperature of three different substances

    I've been asked to find the final temperature of different in an insulated container. A combination of 0.25kg water at 20C, 0.4kg aluminum at 26C, and 0.1kg copper at 100C are combined, and allowed to come to thermal equilibrium. Finding the equilibrium temperature for two substances is...
  6. 1

    Why the wire burns in short current with flow of current?

    In short circuit it is said that there is no resistance. So the current produce heat and wire is burnt. But as the rise in temperature increase the resistance then in short circuit heat must rise the resistance. How can we say there is no resistance in short circuit?
  7. E

    Calculating Luminosity and Temperature of the Sun from Pluto

    Hey all, I think that I'm doing this problem correctly but I'm getting an answer that's a couple thousand Kelvins off. Sorry if I should have posted this in the "advanced" section. 1. Homework Statement Part of a flat region of Pluto has the Sun directly overhead. Its surface temperature is 58...
  8. W

    Power and rate of photon emission with a given temperature

    Assuming that your surface temperature is 99.1 F and that you are an ideal blackbody radiator (you are close), find (a) the wavelength at which your spectral radiancy is maximum,(b) the power at which you emit thermal radiation in a wavelength range of 1.0 nm at that wavelength, from a surface...
  9. T

    Heat transfer through finite temperature difference

    Hello, Heat transfer through finite temperature difference is known a irreversible process because heat cannot be transferred from cold to hot temperature without doing any additional work. But, how this transfer affect the efficiency of the system? How this heat transfer decrease the amount of...
  10. S

    What would happen if an object of 689 degrees was in a room

    I was just thinking, If suddenly an object goes about 689 degrees Fahrenheit (365 degrees celsius) in a room, about which perimeter would human life be impossible ?
  11. B

    High Temperature electrochemical measurements

    Hi all, I'm interested in high temperature sample holders of electrochemical measurements especially for Li-ion batteries. But I couldn't find one. Does anyone use it before? Best regards
  12. J

    Equilibrium temperature with 2 states of matter

    35g of h2o(g) at 380K flows into 300g of h2o(l) at 300K. Cp(l)=4.18kJ/K*kg and ΔH(condensation)= -2257kJ/kg. I need to calculate the final temperature when the system reaches equilibrium. Is the heat capacity for the h2o gas different than h2o liquid? Can you calculate heat capacity using...
  13. H

    Pair instability supernova pressure and temperature question

    I read a scientific journal article that discusses pair instability supernova - I am puzzled about something discussed in the article. If the collision of atomic nuclei and energetic gamma rays produces electron and positron pairs which reduces the pressure inside a supermassive star's core -...
  14. yousaf nasir

    What type of pressure and temperature sensors should I use?

    hello. My FYP is to observe the behavior of a valveless pulse jet by changing shape and dimensions of combustion chamber( i am keeping the volume of combustion chamber constant). i need to know what type of sensor should i use for temperature and pressure measurement. I mean temperature should...
  15. Charles CL

    Exit temperature of cooling pond

    Dear All, Referring to the subject above, I have found the calculation of heat load based on [Lawrence,K.W., Norman, C. P. & Yung, T. H. (2005). Advanced Air and Noise Pollution Control. Totowa: Humana Press.] My cooling pond system: 1. Purpose: cooling POME temperature from 70 to 40 degree C...
  16. H

    How to find equilibrium temperature of a system

    Homework Statement A gas is in an insulated box, which is divided into two portions by an insulated partition. There are n1 moles of the gas at temperature T1 in volume V1, and likewise n2 moles of the (same) gas at temperature T2 in volume V2. The partition is composed of two layers; one...
  17. I

    Decrease in temperature and pressure of closed container

    Homework Statement Helium is stored in a tank initially at temperature To and pressure Po. It starts coming out through an opening (pipe outlet) at a constant mass flow rate of mdot. Calculate the decrease in temperature and pressure of the tank (assuming no heat loss to the surroundings) as a...
  18. R

    High temperature spiral sleeves

    Hi. I want use high temperature spiral sleeves which should withstand around 300 deg C and I want wrap these sleeves around power cables which are passed in enclosure having thermal block and we will heat this block up to 400 deg C Please suggest me how to overcome and suggest best suitable...
  19. D

    Dimensional Analysis? Involving Temperature

    I was trying to convert a quantity in BTU/(ft*hr*F) to W/(m*C) and I can do it just fine by using a conversion factor from a table online, but what I want to know is how to come up with that conversion factor. The conversion factor I looked up and have been using is 1 BTU/(ft*hr*F) = 1.73...
  20. jeremyskate

    Thermodynamics resistance temperature scale

    Homework Statement IMPORTANT:There is an error in the statement.α and β are in C not K 2. Homework Equations R=Ro(1 +αt+βt2) The Attempt at a Solution I really don't know what to do because if I isolate t in the equation it will give me the temperature on the ideal gas scale whereas the...
  21. Chrono G. Xay

    Tension (and Frequency) with Change in Temperature

    At one point I had been trying to construct an equation which would calculate the tension on a tuned string with a change in temperature (and therefore the fundamental frequency), but found my calculations were wrong. By extension, the purpose of the project was to be able to calculate what...
  22. Paulene Gueco

    Change in temperature determine the viscosity of honey

    Have you ever tried to eat honey that has been in the refrigerator - hopeless huh? Both the viscosity and the density of honey change with temperature and water content and I'm told the viscosity and temperature follow a inverse cube relationship. Honey is mostly sugar (glucose/fructose and...
  23. J

    How to calculate surface temperature of earth?

    Assumption: Earth is a perfect blackbody. This means that the emissivity (ε) is 1. Earth’s radius = 6371 km Incident solar radiation = 1367 W/m2 Temperature in space = 0 K I'm given the above data. I tried using the E= σεTe4 but that doesn't include the radius of the Earth :S Im really...
  24. Mnemonic

    Thermodynamics relating to temperature and phase changes V.2

    Homework Statement Suppose a room with 75 m3 of air also contains 80 kg of glycerol and the initial temperature in the morning is 16 °C. If 1.2 kWh of heat is added to the room between morning and afternoon, calculate the final temperature of the air in the room in the afternoon. Use 18 °C for...
  25. Mnemonic

    Thermodynamics relating to temperature and phase changes

    Homework Statement Suppose a room with 75 m3 of air also contains 80 kg of glycerol and the initial temperature in the morning is 16 °C. If 1.2 kWh of heat is added to the room between morning and afternoon, calculate the final temperature of the air in the room in the afternoon. Use 18 °C for...
  26. dykuma

    Mass, Temperature, and Relativity?

    By how much (in picograms) does the mass of 1 mol of water at 0° c differ from the mass of 1 mol of ice at 0° c? 1 mol of water = (assuming) 1 mol of ice = 18 g = 1.8E13 pg So, is this a trick question? The logic of a trickster would tell you that there would be no difference, if one assumes...
  27. Pouyan

    Final temperature of ice mixed with water

    What will be the final temperature of 3.00 kg of crushed ice with temperature -3.0 C mixed with 4 liters of water with temperature 10.0 C? We can ignore all the energy exchange with the environment What I do know and I do: the weight of the ice = 3 kg Ice temprature = -3 C melting energy = 3...
  28. Rectifier

    Nitrogen in a cylinder - temperature, work and volume

    This problem was translated from Swedish, sorry for any grammatical errors. The problem A cylinder with nitrogen gas inside is closed by a tight piston (that can slide without friction against the walls of the cylinder). The piston weighs ##s=12.5 kg## and holds the ##m=28## grams of nitrogen...
  29. C

    Standard Temperature Notation for Phase Change

    °Thought just occurred to me.. Is there a standard way of referring to temperature either of a phase change? For example if I write.. "1kg of water is cooled from 20°C to 0°C, how much energy was removed?" ...then potentially two answers might be considered correct depending if you include...
  30. D

    How can i measure the plasma temperature

    Hi there i wonder how can i measure the plasma temperature ? and what is magnetic field have the impact to plasma or not? Thank you all.
  31. W

    Find the equilbrium temperature

    Homework Statement The thermal conductivites of the materials are 2k,k,4k respectively. Find the equilibrium temperature at X-Y Y-Zhttps://scontent-kul1-1.xx.fbcdn.net/hphotos-xpt1/v/t34.0-12/11950919_10204794824222021_851218095_n.jpg?oh=c15562066e063b2b164fbe7255d7d5d2&oe=55E9175C Homework...
  32. C

    How Does Temperature Relate to Thermal Energy and Kinetic Energy?

    Is the following correct? Temperature is the measure of how hot or cold something is; not how much thermal energy it has. Examples; 1 kg of boiling water has a temperature of 100 degrees C and has heat energy of 4.184 kJ (the specific heat capacity of water). 1 kg of lead heated to a...
  33. P

    How to maintain commercial scale CSTR temperature?

    I'm currently doing a design for my final year studies and it's regarding esterification process. My proposed reactor is CSTR, operating at a temperature of 60C and 400 kPa. Reactants are methanol and jatropha oil with sulphuric acid catalyst. For a commercial scale production of biodiesel...
  34. C

    Thermodynamics of mercury thermometers

    The space above the mercury column in a thermometer ordinarily is evacuated, but due to faulty manufacture, a particular thermometer has a pressure of 2 mmHg of air in this space when the whole thermometer is immersed in a bath at 0 degrees Celsius. Calculate the pressure of the air when the...
  35. Borek

    Melting Nickel Ball: Temperature & Radius Effects

    How far down can a nickel ball of radius r and temperature Tn melt into the ice block of temperature Ti? Watch the video and state your assumtpions...
  36. Andre

    Average surface temperature independent of radiative gasses?

    http://www.sciencedirect.com/science/article/pii/S0273117715005712 from the abstract: Obviously, the most prominent missing 'forcing' parameter here, is "concentration of greenhouse gasses". There is probably some food for thoughts here, especially when the analysis of Den Volokin and Lark...
  37. Nantes

    If the air temperature were the same as the human body's....

    Damn title character limits. I just had the weirdest thought while rearranging my computer's case fans. I put my hand in front of one of them and felt a light breeze of air, telling me it was working. This is due to the local cooling produced where the fan's airstream comes in contact with the...
  38. P

    Air flow from large to small tube.What happens to pressure?

    I would like to know what happens to air pressure when it flows from large tube to small tube. I would like to know the basic science behind this though I am pursuing my B.E. Moreover, does PV=mRT law apply here or some other principle applies here. What happens to temperature and other...
  39. Rodwen

    Light absorbtion and change in temperature of liquids

    Hi hi, Sorry if this is awful and boring. Basically what I want to work out is a way to differentiate two different liquids by touch (specifically, temperature) after shining a light on them. A thermometer cannot be used. The variables open here are the compositions of the liquid (I'm going...
  40. P

    Thermodynamics -- Calculate the pressure and temperature

    Homework Statement A rigid vessel of volume 5m^3 contains 1.0 kg of water and steam at 19 degree C.Find the pressure and the mass of liquid and vapour in the vessel. The vessel is now heated unit the water is just evaporated. Calculate the the pressure and temperature of this process. The...
  41. kester

    Effect of temperature on the heat of combustion

    Like in a topic. I just got this question and I am looking for some help. I found this one http://wikieducator.org/The1stLawofThermodynamicsLesson5 I don't know, is the heat of combustion is the same as entalphy?
  42. A

    Hydrogen/Helium Emission Spectra Temperature Dependence

    Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...
  43. Stephanus

    Earth Core Temperature: Causes & Impact

    Dear PF Forum, Does the Earth core produces its own energy? If it is true, how? Radioactive decay? Gravity? Earth core temperature is around 4000 Celcius. Almost like the sun surface temperature. How can that temperature kept for 4 billions of year? Can the temperature heat the mantle and Earth...
  44. D

    Temperature increase in a fixed volume when adding mass

    Hello, I'm interested to know if that in a fixed insulated volume (e.g. 500ml), at some temperature (e.g. 293K) and pressure (e.g. 1 atmosphere), and you increase the pressure by a specific amount by pumping more gas (e.g. air at 293K) into the volume can you work out the expected increase in...
  45. A

    Interpreting Kinetic Temperature for Solids / Liquids

    Hi all, I'm brushing up on some thermodynamics, and having been reading up on the interpretation of temperature as derived from kinetic theory. I can follow the derivation for an ideal, monatomic gas which relates temperature to the average, translational kinetic energy of the molecules. Most...
  46. B

    How room temperature will change in 1 hour

    Hello, having the following data can I somehow calculate how will the temperature in room change in 1 hour time? room length = 6m room width = 6m room height = 3m lets say radiator is 0.5m x 1.5m and has 2000W and it can be in 2 states: on/off I have also the current air temperature and...
  47. A

    Axial Deformation due to Temperature Change and Load

    Homework Statement A 100 kN load is applied to a flange positioned midway (at B) along a 50 mm diameter steel bar (ABC). The bar is placed between two rigid supports and is thus constrained. Determine the position of the flange (distance from the left support) if the temperature of the bar...
  48. R

    Temperature for 3 or 4ft underground

    There are often talks of ground temperature being a constant 55F at 6ft or so. But some also said that in very hot and dry climate, say Arizona desert, temperature is much higher at the same depth. Anyone has any idea of underground (4ft? under) temperature in dry hot desert? Thanks
  49. C

    Questions on keeping a house cool

    Hi guys, I have a question on cooling the house. So at night, I usually open windows to let all of the cold air come in and open the 2nd floor windows to let the hot air out. The 2nd floor is a large open area and has windows in the front and windows in the back. Now, I normally open all the...
  50. Y

    Thermally insulating tape at high temperature (350C)

    Hi all, I am looking for a tape or gel that is very thermally insulating and apply that on my glass slide to serve as a thermally insulating material. The work temperature is 100C to 350C and it should be able to work with clean water. Any recommendations?
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