# What is celsius: Definition and 55 Discussions

The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale or a unit to indicate a difference or range between two temperatures. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a variant of it in 1742. Before being renamed in 1948 to honour Celsius, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. Most countries use this scale; the other major scale, Fahrenheit, is still used in the United States, some island territories, and Liberia. The Kelvin scale is of use in the sciences, with 0 K (−273.15 °C) representing absolute zero.
Since 1743, the Celsius scale has been based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure. Prior to 1743 the values were reversed (i.e. the boiling point was 0 degrees and the freezing point was 100 degrees). The 1743 scale reversal was proposed by Jean-Pierre Christin.
By international agreement, between 1954 and 2019 the unit degree Celsius and the Celsius scale were defined by absolute zero and the triple point of water. After 2007, it was clarified that this definition referred to Vienna Standard Mean Ocean Water (VSMOW), a precisely defined water standard. This definition also precisely related the Celsius scale to the scale of the kelvin, the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. Until 19 May 2019, the temperature of the triple point of water was defined as exactly 273.16 K (0.01 °C).On 20 May 2019, the kelvin was redefined so that its value is now determined by the definition of the Boltzmann constant rather than being defined by the triple point of VSMOW. This means that the triple point is now a measured value, not a defined value. The newly-defined exact value of the Boltzmann constant was selected so that the measured value of the VSMOW triple point is exactly the same as the older defined value to within the limits of accuracy of contemporary metrology. The temperature in degree Celsius is now defined as the temperature in kelvins subtracted by 273.15, meaning that a temperature difference of one degree Celsius and that of one kelvin are exactly the same, and that the degree Celsius remains exactly equal to the kelvin (i.e., 0 °C remains exactly 273.15 K).

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1. ### Why must we use absolute temperature for the Ideal Gas Law?

For this problem, The solution is, However, why must we use absolute temperature for the ideal gas law (i.e why can we not use Celsius for T) Many thanks!
2. ### Why do we not need to convert from degrees Celsius to Kelvin?

I understand that the Kelvin scale begins at absolute zero and that the Kelvin scale may even be referred to as the absolute scale. As the units begin from a definite zero and increase with equal amounts of energy being added to the particles of the substance being measured (at equal intervals...
3. ### Why does Celsius temperature in degrees have +/- signs, since it's scalar?

Why does Celsius degrees have +/- signs, since it's scalar?
4. ### Adiabatic PVT relationships - why Kelvin and not Celsius?

Homework Statement Here's a derivation of the adiabatic PVT relationships. QUESTION: When solving adiabatic PVT homework problems I found that I needed to express temperature in Kelvin, rather than Celsius, to get the right answers. Where in this derivation should this be specified, and how...
5. ### MHB When the temperature when degree Celsius is equal to degree Fahrenheit

Q7, b is where I got stuck
6. ### B When Difference between Kelvin and Celsius are negligible

This question is more for practicality than anything else, and I realize it may be partly subjective. At what temperatures can the 273 degree difference between Kelvin and Celsius scales be ignored? I'm thinking for examples regarding stars and very high temperatures. Surely once you get to 15...
7. ### Difference between using temperature in Celsius and Kelvin

For one my homework questions I was asked to find the specific heat capacitance of a certain material. The specific heat capacitance has a temperature dependence given by: c = 0.20 + 0.14T + 0.023T2 the units for T is temperature in Celsius and c is measured in cal/gK. 2.0 g of the material was...
8. ### Celsius to Kelvin conversion problem (Kinetic theory)

Homework Statement Find the temperature T that allows the rms speed of a gas to be equal to another gas with T=47°C. The molecular mass of the first gas is 64, and the molecular mass of the second gas is 32. Homework Equations v_{rms}= \sqrt{\frac{3RT}{M}} The Attempt at a Solution The...
9. ### How to heat a plasma to 10^8 degrees Celsius

Recently, Germany broke headlines when they fired up their nuclear fusion reactor. As I'm sure most everyone on this forum knows this, they plan on creating fusion by heating plasma to absurd temperatures while containing it in a magnetic field. What method do they use to heat the gas and...
10. ### Convert Change in Temp from Celsius to Fahrenheit

Homework Statement Consider the apparatus that Joule used in his experiments on the mechanical equivalent of heat, shown in the figure below. Suppose both blocks have a mass of 0.69 kg and that they fall through a distance of 0.45 m. Homework Equations (a) Find the expected rise in temperature...
11. ### C program using functions to convert Fahrenheit and Celsius

Homework Statement Hi i have an assignment that is asking me to convert 3 temperatures in fahrenheit to celcius and vice versa. I am very new to programming only 2 weeks in(and i learn by playing with the program) so I do not know all of the terminology / principles. I am not allowed to use...
12. ### How Does a Glass Beaker Withstand 1000 Degrees Celsius?

The temperature at which the process is carried out is around 120 degree centigrade, however in the interior , the reaction temperature goes to around 1000 degree centigrade. How is it then , that the glass beaker in which the synthesis is carried out does not crack even at such high...
13. ### Celsius to Kelvin Conversion: Solving for T2

Homework Statement At constant volume and number of moles T1/T2=P1/P2 As per ideal gas equation So given data is T1=27 degree celcius P1=80 Cm ,P2=120 Cm T2=? Homework Equations T2=P2/P1 multiplied T1 The Attempt at a Solution :120 cm/80cm multiplied by 27 degree celcius =40.5 degree...
14. ### Celsius and Farenheit question

It's a quick question---just trying to resolve an argument between me and my friend--to convert Celsius temp. to Farenheit, one simply multiplies Celsius temp. with 5/9 and subtract by 160/9, NOT double the Celsius temperature and add 30, right? Please tell me which one is correct, for I think...
15. ### Boiling Water Temp: Celsius vs. Fahrenheit

Homework Statement A Celsius and a Fahrenheit thermometer are dipped in boiling water. The temperature of the water is brought down until the Fahrenheit thermometer reads 140°. So, the fall in temperature registered by Celsius scale is: 30 40 50 80 Homework Equations F=(C*(9/5))+32...
16. ### Calculate equilibrium dissolved oxygen at 19.8 Celsius

Homework Statement 1. Calculate the equilibrium dissolved oxygen concentration for each temperature if PO2 = 21% (this means that if atmospheric pressure is 1 atm then O2 pressure is 21% of that) Homework Equations K19.8/RT = Kp PV=nRT The Attempt at a Solution K19.8/RT = Kp K19.8 =...
17. ### C/C++ C++. Celsius to Fahren. conver; What temp R they = ?

I must write a program that finds the temperature, as an integer, that is the same in both Celsius and Fahrenheit. The formula for this is F=(9/5)C+32 The program should create two integer variables for the temperature in Celsius and Fahrenheit. Initialize the temperature to 100 degrees...
18. ### Best Material to conduct thermal heat from water at 50 degrees celsius

I am trying to figure out what kind of material would be best used in order to transport water through a material that would be the same size/shape/diameter of a conventional pipe inside a home running water. The idea is that the water running through the pipe would be at a temperature of...
19. ### How much warmer is 10 degree Celsius than 5 degrees Celsius?

Hi everyone- this is my first post on the Forum. I'm a H.S. Mathematics teacher with a reasonable understanding of basic Physics for someone with no degree in the subject (Treat me like a solid H.S. Physics student in terms of my understanding). So I was in Canada this past week, and I began...
20. ### Energy required to heat up a 4000 cm^3 of air to 1500 Celsius

Hello, I have been struggling to calculate the joules required to heat a sealed chamber (cuboid shape 20x20x10cm=4000cm^3) filled with Air from room temperature to 1500 Celsius and couldn't get any straight answers from my calculations...! Considering this chamber (which is actually an...
21. ### Find the final Celsius temperature of the aluminum and water

Homework Statement A 2.3kg aluminum pan at 135° is plunged into 3.0kg of water at 15°. The specific heat of aluminum is 900 J/(kg K). Part A Find the final Celsius temperature of the aluminum and water. T_f = °Celsius Part B Find the entropy change of the aluminum pan...
22. ### How much does 1m^3 oxygen at 10 bar weight at 0 degree celsius?

Homework Statement How much does 1m3 air (oxygen) weight with 10 bar pressure at 0 degrees celsius? Homework Statement 0 degrees Celsius = 273.15 kelvin The Attempt at a Solution I saw this formula on another thread: 1 atm = 101,325 pascals ~ 1.2 atm = 121,590 pascals 27oCelsius = 300.15 K...
23. ### Insulated Copper Block Heated to 60 Celsius

Homework Statement An insulated copper block receives energy at a rate of 100 W from an embedded resistor. If the block has a volume of 10-3m3 and an initial temperature of 20°C, how long would it take, in minutes, for the temperature to reach 60°C? Homework Equations Copper specific...
24. ### To increase the temperature of 50 grams of water by 2 Celsius degrees requires

Homework Statement To increase the temperature of 50 grams of water by 2 Celsius degrees requires? Homework Equations The Attempt at a Solution As I understand it takes one caloric to increase 1 gram of water to 1 *C..Correct? since its 50 grams raised by 2*C, I have 50x2= 100 calories?
25. ### Fahrenheit vs Celsius: Should Americans Embrace the Celsius Scale?

A meteorologist friend of mind told me a story about an American who owned a condominium overseas. The owner got an email from the caretaker saying the temperature in his condo was 32 degrees and for asked permission to turn on the air conditioning and set the thermostat to 28. The owner...
26. ### 273 + degree Celsius = Kelvin Why 273?

Temperature conversion: 273 + degree Celsius = Kelvin Actually why is that 273? How does one come up with this? My teacher mentioned gann's law(not sure if this is the one) but i couldn't find anything related to this, which law should it be? Thanks in advance.
27. ### Speed of sound in water at 16 degrees celsius

Homework Statement How do you calculate the speed of sound in water at 16 degrees celsius? Homework Equations Speed at 20 degrees is 1482m/s The Attempt at a Solution I need help getting started... I don't know how to go about trying to work this out (this isn't a homework...
28. ### Temperature change in Celsius from Fahrenheit value

Homework Statement a) One day, the temperature outside changed by 13.7 degrees on a Fahrenheit thermometer. By how much did the temperature change on a Celsius thermometer? Homework Equations F = (9/5)C + 32 The Attempt at a Solution F2 - F1 = 13.7 (9/5)C2 + 32 -(9/5)C1 + 32 = 13.7...
29. ### How can I improve my Celsius to Fahrenheit Converter code?

#include <iostream> using namespace std; int main() { cout<< "Roll Cast's Celsius to Fahrenheit Converter\n Please enter the minimum temperature in celsius\n"; double min; cin>> min; jump: cout<< "Please enter the maximum temperature in celsius\n"; double...
30. ### Why every gas would exert zero pressure at -273.15 degree celsius

I was reading about the experiment of constant volume gas thermometer today. When we extrapolate the presuure -temperature lines, the lines would meet at point -273.15 degree celsius, which is zero presure. I was wondering whether it is a matter of coincidence or some science behind it. The...
31. ### 0 Celsius for ais , 100 Celsius for boiling water ?

0 Celsius for ais , 100 Celsius for boiling water ? As we know that is common for study. But anyone know where is origin ? What i mean is ...is it valid at every country ?
32. ### Will Two Thermometers in Water at 50 Celsius Have the Same Temperature?

I was wondering; if a water is say at a temperature of 50 Celsius and we put two thermometers into it, one which is a mercury in glass and the other which is of alcohol (same mass of both constituents); when we break the thermometers directly after the readings are stabled and we measure what...
33. ### Uncertainties question (Kelvins and Celsius)

Turns out there is a problem with the question. Thanks though.
34. ### MIPS Help. Fahrenheit to Celsius

# Fahrenheit to Celsius .data # following are data prompt: .asciiz "\nPlease input degrees in fahrenheit: " # prompt user for input result: .asciiz "\nDegrees in celsius is: " # display degrees in celsius bye: .asciiz "\nProgram terminated" # display when program terminates...
35. ### RHIC Collider Creates Quark-Gluon Plasma at 4,000,000,000,000 Degrees Celsius

What are your thoughts? Apologies if this is in the wrong place... http://www.popsci.com/science/article/2010-02/rhic-collider-creates-72-trillion-degrees-fahrenheit-quark-gluon-plasma"
36. ### Water vapor at approx. 300 degrees Celsius

Ive heard that at somewhere around 300 degrees Celsius (cant remember the exact number), you can't liquidise it anymore. Is this fact correct? Thanks in advance, fawk3s
37. ### [Thermodynamics] Relative fractional error, Ideal-gas-scale, Celsius scale

Homework Statement http://j.imagehost.org/0069/thermo.jpg Homework Equations The Attempt at a Solution OK, so I tried to derive θ in respect to r as in θ(r): \frac{d\theta}{dr} = \frac{-100}{(r - 1)^2} Then, I multiplied both sides of the equation by 'dr', d\theta = \frac{-100}{(r -...
38. ### Specific Heat Problem in Celsius

Homework Statement The specific heat of substance X is 200 J/g*C, how much heat is required to change the temperature of 2.0 kilograms of substance X from 40 degrees Celsius to 55 degrees Celsius? Homework Equations Q=(m)(c)(change T) The Attempt at a Solution 55 C-40 C= 15 C...
39. ### Doubling Celsius temp also double the pressure?

Does doubling the Celsius temp of a container also double the pressure? I know it's true for Kelvin but I'm not sure about Celsius.
40. ### From Celsius to Kelvin - why +273?

Hi, I am puzzled by the use of the number 273 when converting from Celsius to Kelvin and vice versa. I know that Celsius scale is based on ice point and steam point, whereas Kelvin scale is based on triple point of water, which is very very close to ice point. I am a teacher and i was...
41. ### Why we would 32 in Celsius to Fahrenheit & Vice Versa

Why we would 32 in Celsius to Fahrenheit & Vice Versa. Hey fellows, please tell me why we add 32 to celsius to Fahrenheit conversion and vice versa. According to my mind, I derive C to F formula of my own. I do the following.1)I look and choose the same scale of F and C. The most obvious of...
42. ### Absolute Zero on celsius scale

Hi , Please help me to solve following problem. If 20 KJ are added to a carnot cycle at a temperature 100 degree Celsius and 14.6 KJ are rejected at 0 degree Celsius,determine the location of absolute zero on celsius scale? Ans -270.16 C Please tell me how to solve it Thanks in...
43. ### Temperature scale: When will Celsius and Faranheit scales agree with each other?

Homework Statement Calculate the one temperature at which Fahrenheit and Celsius thermometers agree with each other. Homework Equations TF = TC * (9/5) + 32°C TC = ( TF + 32 ) * (5/9) TK = TC + 273.15 The Attempt at a Solution *Shrug* I can't even understand how to set it up... 4. The...
44. ### Converting Fahrenheit & Celsius: A C Programming Guide

Okay. I need to write a C program to convert between fahrenheit and celsius degrees.
45. ### Converting Celsius to Kelvin Easy but slightly confusing

Homework Statement I'm doing calorimetry, and I have 34.73C and 63C. I need to subtract 63 from 34.73, and get the answer in Kelvin. Homework Equations The Attempt at a Solution I know you add 273 to Celsius values to get Kelvin, but I am not sure which of these methods is correct: 1...
46. ### Achieving -40 to -50 Degrees Celsius: Solutions & Alternatives

Hi, I am doing some undergraduate work in Sweden, and for one of my tests, I need to place a material at -40 to about -50 degrees Celsius for a short period of time for thermal cycling. Unfortunately, my access to equipment is rather limited here The current method we're using is just wrapping...
47. ### Kelvin Temperature - Celsius Temperature Change

Hello, I'm going to post a curious question. Today I found a case where I have no idea what to do. I'm working with the Thermal Conductivity and it's W/(m ºC) or W/(m K) then I don't know how to change from a way to the another one because kelvin and Celsius degrees are not...
48. ### Why Must We Use Absolute Temperature for Ideal Gas Law?

Question Why must we use absolute temperature in the ideal gas law (PV = NkT)? Why using the Celsius scale would give nonsensical results? I am not sure what is the reason, can anyone helps?
49. ### Do Canadians wear short sleeves shirts at 12 degree Celsius?

I am a HongKonger. My chemistry teacher comes from Canada and he wears short sleeves shirt every day, even when the temperarure is 10 degree Celcius. May I know is it true that Canadians still wears short sleeves shirt at 10 degree Celcius? I feel freezing. They are very strong...
50. ### How many grams of water at 20 degrees Celsius can be converted into steam

can someone give me a hand on this one? How many grams of water at 20 degrees Celsius can be converted into steam at 500 degrees Celsius with 10 kJ of energy? wat i know is that this question is 2 parts: Water being heated to 100 C (80 C change)using the specific heat of water n then...