# Homework Help: Question about Q=mcΔT when doing calorimetry

1. Nov 7, 2011

### deezer

1. The problem statement, all variables and given/known data

When using the equation Q=mcΔT for the substance being tested is it the mass of the substance or the mass of the substance + mass of water.

2. Relevant equations

3. The attempt at a solution

So when I solve calorimetry problems, I usually find Qwater. Then I set Qsubstance=-Qwater. But then I have to use mcΔT, I'm not sure if it's the mass of the substance or the mass of the substance + mass of the water because I've gotten a few questions wrong and the textbook briefly mentioned the sum of masses but gave no examples. Thanks for your input.

2. Nov 7, 2011

### edgepflow

c = $\frac{Q}{mΔT}$

Since 'c' is for the substance, what would 'm' be for?

3. Nov 8, 2011

### deezer

m is for the substance right? Not the sum of the mass of the water and substance.

4. Nov 8, 2011

### edgepflow

Yes, and you can relate to the definition of specific heat: energy required to raise the temperature of one unit mass of the 'substance' on unit degree.

5. Nov 8, 2011

### Staff: Mentor

Like specific heat of brine :tongue: