Calculating q

[charliea100]

Hi,
How do we know when to use K or C when calculating q? In some questions of the Achieve HW (#18), we used the delta T using C, but for #19, we used the delta T using K. Does the units of degrees not matter or is there something else to it?

[Tiffany Wang 3L]

Delta t can be either Kelvin or Celsius, but you just have to make sure that the units for c in the equation q=mcΔt match. This way, you can cancel out that temperature unit when calculating q. For example, if Δt is in K, then the units of c must be J/(kg K). If it was in Celsius, then the units of c must be J/(kg °C).

[Elizabeth Park 1B]

When you are calculating delta T, the units of the degrees don't really matter. You will get the same answer either way because in order to change the units from degrees Celsius to Kelvin you use the equation °C + 273 = K. In other words, the final temperature minus the initial temperature will still be the same. However, if you want your work to be technically correct, you should use the right units when applicable.

[Yasmin Moosavy1A]

delta just stands for change, so the Final - Initial of something. So when you do change in temp. the units don't really matter as the difference between the final and initial will be the same for both K and C. Usually you solve using K as it is SI but if the units of your constants involve something else, adjust accordingly.