In problem 31 we use the formula nCdT=nCdT. Why is it that for dT for water at 0 degrees we find change in Temp using Tfinal-Tinitial whereas for water at 100 degrees we use Tinitial-Tfinal. Aren't the initial Temps. of the water 0 and 100 degrees and then the 100 degree water cools down to the final temperature of the solution of water. Why don't we use 100-Tfinal? I think I am probably making the wrong assumptions about this, but I have managed to become confused by it. Sorry if I am not making sense here!....

-- Anonymous, February 29, 2000

Answers

The reason you switch around Tintial and Tfinal is to keep both answers positive. I think if you do final minus intial both times you will get the same answer but you have to be careful and watch your signs. Since it is a difference you are measuring the absolute value does not change.

I hope that clears things up. feel free to ask if you need more explaination.

-- Anonymous, February 29, 2000