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<center>Notes on Heat Calculations</center> 
 
Steps to Calculating Heat (Thermodynamic) Problems: 
 
Before Step 1. Define your system (the substance(s) that are changing).

1.	Write down unknown information (i.e. what you are looking for).

2.	Write down what you know. Remember if you are given heat value (in cal or J) you need to determine the sign of this value:

*What to do with heat term
**If system is losing heat (giving to surrounding), the heat sign is negative
**If system is gaining heat (absorbing from surrounding), the heat sign is positive
**If you are calculating the heat value, you don't determine the sign your calculations will

*What to do with temperature and temperature change
**Show You must show Tinitial and Tfinal
**,Show calculation, &#916;T = Tfinal - Tinitial HERE including sign
**If your unknown is either Tinitial or Tfinal, see special case below

3a. Setting up answer: By equation (Following steps from [[Set-up for Equations Notes]]) 
*Equation for Phase change (called Latent heat) heat equation (equ): In class 
*Equation for Non-phase change (calledSensible heat) heat equ: &#916;H = ( m ) ( &#916;T ) ( c ) 
**where &#916;H is heat change, &#916;T is temperature change and c is specific heat capacity ( J/(g-&deg;C) or cal/(g-&deg;C) )

3b. Setting up answer: By Dimensional Analysis (Following steps from [[Dimensional Analysis Notes]] 
*Important information is that c (specific heat capacity) is conversion: unit for c = J/(g-&deg;C) or cal/(g-&deg;C) )

4.	Do math. (make sure to have units on all numbers and keep appropriate sig fig and scientific notation).

5.	Check answer including correct number of sig figs, scientific notation, and proper units! Remember that the last calculation step determines the method of determining sig figs. 
 
Example of Work 
*[http://www.tmcleod.org/Level1/Chem328IntroEnergy/Chem328HeatCalculationMostBasicExampleofWork.pdf Example of Work for Most Basic Heat Calculations]
*[http://www.tmcleod.org/Level1/Chem328IntroEnergy/Chem328BasicHeatCalculationExampleofWork.pdf Example of Work for Basic Heat Calculations]
*More Complicated or Advanced Problems (Usually Honors Learner) 
**[http://www.tmcleod.org/Level1/Chem328IntroEnergy/Chem328HeatCalculationSignMattersExampleofWork.pdf Example of Work for Heat Calculation where Sign of Heat Matters]
 
 
Special Case When Looking for Tinitial and Tfinal

For these problems, the actual equation/math you are trying to solve is not the heat equation &#916;H = (m)(&#916;T)(c) but &#916;T = Tfinal - Tinitial
 
So, you will need to change the above equation to either: 
* Tfinal = &#916;T + Tinitial or 
*Tinitial = &#916;T - Tfinal 
 
You first need to determine the deltaH. This can be done by either Dimensional Analysis or Equation. Once you have calculated &#916;H, you now all information to calculate the difference above and find answer. 
*Note: since last math step is add/subtract, you will need to do columns/decimal places not number of sig fig to get answer in correct sig figs. 
 
Example of Work 
*[[http://www.tmcleod.org/Level1/Chem328IntroEnergy/Chem328HeatCalculationFinalTempExampleofWork.pdf Example of Work for Heat Calculation for Initial or Final Temperature]]

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