1. How Does Thermodynamics apply to reactions and nutrition?

2. Chemical Calorimetry

3. It Heats Up Coffee!!!!

4. Chemical Calorimetry Calorimeter – a device used to measure the heat absorbed or heat released in a chemical or physical change – Data acquired using a calorimeter is changes in temperature which is then used to calculate heat

5. Types of Calorimeters Simple Calorimeter Coffee Cup Calorimeter

6. Bomb Calorimeter

7. Calorimetry for determining ΔH Adiabatic Calorimetry – method of measuring the heat absorbed or released in a chemical or physical change in which no heat is allowed to enter/leave the system Using calorimeters scientists test substances for their combustion – after combustion the increase in temperature causes an increase in temperature for the surrounding area and with this temperature increase the molar enthalpy ΔH is determined

8. Hess’s Law allows us to combine enthalpy changes Hess’s Law – the overall enthalpy change in a reaction is equal to the sum of the enthalpy changes of the individual steps in the process If the heats of reaction for the partial reactions are known, then they can be combined to give the heat change for the overall reaction

9. Lets Practice that stuff

10. Hess’s Law can also be applied to entropy calculations Table A-13 in your book also have the molar entropy values. All entropy values can be determined and all values are given at standard temperature (25* C)

11. Practice:

12. Gibbs Free Energy Gibbs Free Energy – can be calculated in 2 ways – Using the eqn. - ΔG⁰ = ΔH ⁰ - TΔS⁰ – Or using Hess’s Law – Sum of Products – Sum of Reactants If ΔG is….. PositiveNot Spontaneous ZeroNeither Direction is Favored NegativeSpontaneous

13. ΔHΔHΔSΔSΔGΔGIs it Spontaneous? Negative (Exo)Positive (disorder) NegativeYes Negative (exo)NegativeEither + or -Only at T < ΔH/ΔS Positive (endo)PositiveEither + or -Only at T > ΔH/ΔS Positive (endo)NegativePositiveNope

14. Homework Practice Problem 1 on page 408, except use BOTH methods!