## When to use Kelvin or Celsius

Andrew Nguyen 2I
Posts: 68
Joined: Fri Sep 29, 2017 7:07 am

### When to use Kelvin or Celsius

When T is being used in an equation - is there a set rule for when to use Kelvin or Celsius, or any time it is better to use either of the two?

Mitch Mologne 1A
Posts: 74
Joined: Fri Sep 29, 2017 7:04 am

### Re: When to use Kelvin or Celsius

For the most part, in thermochem we use a change in temperature, which means either kelvin or celsius will work considering they use the same scale. That being said, the ideal gas law uses kelvin.

Shanmitha Arun 1L
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### Re: When to use Kelvin or Celsius

For many cases, Kelvin is used but it really just depends on the problem and the units given.

Harrison Wang 1H
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

### Re: When to use Kelvin or Celsius

It depends on the units of the constants in the problem. For example, in a problem that gives molar heat capacity, you would use kelvin, whereas in a problem that gives specific heat capacity, you would use celsius. If no preference is stated, than either or is fine.

siannehazel1B
Posts: 30
Joined: Fri Sep 29, 2017 7:06 am

### Re: When to use Kelvin or Celsius

when you're doing a problem that calls for the change in temperature it doesn't matter what units you use because the difference in temp will be the same no matter what units you're in, but the problem should specify what units if they are needed.

Angel Ni 2K
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

### Re: When to use Kelvin or Celsius

If the equation requires deltaT, then it doesn't matter whether you use K or C. If the equation requires T and not deltaT, then usually you will need to use K. Make sure to keep track of your units and that after cancelling, your ending units are actually what you are looking for.

Nhan Nguyen 2F
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### Re: When to use Kelvin or Celsius

If no preference stated, I think we should use Kelvin since it's more applicable to a lot of thermodynamic problems.

Naomi Jennings 2H
Posts: 21
Joined: Thu Jul 13, 2017 3:00 am

### Re: When to use Kelvin or Celsius

In addition, for entropy you have to use Kelvin, because in the equation you aren't using delta T, you are using T, so multiplying the other terms by 25 (degrees celsius) will get a much different result than multiplying the other terms by 298 (degrees kelvin). In contrast, for a problem asking for delta T, 25-0 (degrees celsius) = 25 degrees C, and 298K - 273K = 25K, so in both cases you multiply the other terms by 25.

Elizabeth Bamishaye 2I
Posts: 54
Joined: Fri Sep 29, 2017 7:04 am

### Re: When to use Kelvin or Celsius

Yes, I agree with all of the responses above because at some point I was thinking about this as well. It really depends on what you are given in the problem and what you have to look for.

Sarah Wax 1G
Posts: 29
Joined: Sat Jul 22, 2017 3:00 am

### Re: When to use Kelvin or Celsius

Everyone posting in this forum is correct. Usually, when using deltaT, it doesn't matter whether you use K or C because a change in temperature for either will result in the same numbers. However, when using just T in an equation, you need to use the other labels in order to determine whether or not the other units use K or C.

soniatripathy
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am

### Re: When to use Kelvin or Celsius

The most important thing to consider in these cases are the units of the constants and given values. This will help you determine if you need to use K or C because you might need to get some of the units to cancel out. i think for things like deltaT either should be fine because they are both scaled the same so the difference would be the same

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