[AfronPie]

Hello,
I was trying to do my chemistry lab whose aim was to find a Calorimeter constant. As a calorimeter, we used two styrofoam coffee cups with a cap on top. We mixed hot and cold water to find the constant. My teacher wrote the equation:
Q(hot water)= Q(cold water) + Q(cal).
For Q(hot) I got -2910J, and for Q(cold) I got 3130J.
Therefore, Q(cal)= -6040J.
When dividing by change in temperature, I got a Calorimeter constant of -241 J/C
I know that Q(cal) should not be negative, and I am pretty positive that I calculated the numbers right. I am confused which numbers are positive or negative. Also, when I looked this up online I found a different formula than what my teacher used which was
-Q(hot water)= Q(cold water) + Q(cal), with a negative
 Which equation is right? Am I messing up something else? Also I tried finding something to compare my number too, but I couldn't. Has anyone found the Calorimeter constant for a styrofoam cups and can post the number they got for it.
Thanks in advance for your time,
Aaron

[Corribus]

It helps if you clearly describe everything you did and especially if you take care to format your posts.

Typically, q_cal = -(q_hot + q_cold)

Where the "hot" and "cold" refer to the substance that starts off hot (usually a piece of metal or something but in your case hot water) and the cold refers to the substance that starts off cold (usually cold water).

You may find the problem here similar enough to your problem to help you out:

http://resources.seattlecentral.edu/faculty/ptran/experiments/chem140/Fall%2005/Experiment%2021%20Calorimeter%20Constant%20Determination.pdf

[AfronPie]

Thank you for your response. I now better understand which numbers are negative.
However, I am still wondering if someone else has done this lab and what they're results were (I have a feeling that I'm either close to the value, or extremely off)
If anyone has calculated the Calorimeter constant for 2 styrofoam cups with a cover and thermometer please share your the number.