1. THERMODYNAMICS
Courtesy of lab-initio.com

2. Units for Measuring Heat
The Joule is the SI system unit for measuring heat:
The calorie is the heat required to raise the temperature of 1 gram of water by 1 Celsius degree
1 L atm = J

3. Definitions #1 Energy: The capacity to do work or produce heat
Potential Energy: Energy due to position or composition
Kinetic Energy: Energy due to the motion of the object

4. Definitions #2
Law of Conservation of Energy: Energy can neither be created nor destroyed, but can be converted between forms
The First Law of Thermodynamics: The total energy content of the universe is constant

5. State Functions depend ONLY on the present state of the system
ENERGY IS A STATE FUNCTION
A person standing at the top of Mt. Everest has the same potential energy whether they got there by hiking up, or by falling down from a plane 
WORK IS NOT A STATE FUNCTION
WHY NOT???

6. E = q + w E = change in internal energy of a system
q = heat flowing into or out of the system
-q if energy is leaving to the surroundings
+q if energy is entering from the surroundings
w = work done by, or on, the system
-w if work is done by the system on the
surroundings
+w if work is done on the system by the
surroundings

7. Energy Change in Chemical Processes
Endothermic:
Reactions in which energy flows into the
system as the reaction proceeds.
+ qsystem qsurroundings

8. Energy Change in Chemical Processes
Exothermic:
Reactions in which energy flows out of the system as the reaction proceeds.
- qsystem qsurroundings

9. Work, Pressure, and Volume
Expansion
Compression
+V (increase)
-V (decrease)
-w results
+w results
Esystem decreases
Esystem increases
Work has been done by the system on the surroundings
Work has been done on the system by the surroundings

10. Enthalpy
H is a state function – ΔH doesn’t depend on the pathway between the two states
H = E + PV,
E is internal energy of the system,
P is pressure of the system, and V is volume of the system.
At constant pressure and knowing only P-V work is allowed (w=-PΔV), we can derive:
-ΔH = q, at constant pressure
ΔH = Hρroducts - Hreactants

11. Example 6.4
When 1 mole of methane is burned at constant pressure, 890 kJ of energy is released as heat. Calculate ∆H for a process in which a 5.8 g sample of methane is burned at constant pressure.
Given: Find: ∆H of the rxn (KJ)
Mass = 5.8 g CH₄
Molar mass CH₄ = g
q of the product = ΔH = -890 kJ/mol CH₄
Find moles of methane:
5.8 g 1 mole = 0.36 mol
16.04g
∆H = .36 mol kJ = -320 kJ, exothermic
1 mol

12. Calorimetry
The amount of heat absorbed or released during a physical or chemical change can be measured, usually by the change in temperature of a known quantity of water in a calorimeter.

13. Specific Heat
The amount of heat required to raise the temperature of one gram of substance by one degree Celsius.
Substance
Specific Heat (J/g·K)
Water (liquid)
4.18
Ethanol (liquid)
2.44
Water (solid)
2.06
Water (vapor)
1.87
Aluminum (solid)
0.897
Carbon (graphite,solid)
0.709
Iron (solid)
0.449
Copper (solid)
0.385
Mercury (liquid)
0.140
Lead (solid)
0.129
Gold (solid)

14. Catalyst (10 mins)
In book: P.277 #49

15. Calculations Involving Specific Heat at constant pressure
q = Heat lost or gained
s = Specific Heat Capacity
T = Temperature change
Assumption: that the density of the solution is the same as pure water, 1 g/mL. Otherwise, a different density will be given.

16. NaOH(aq) + HCl(aq) -> NaCl(aq) + H₂O (l)
Example 1
1.00 x 10² mL of M HCl was mixed with 100. mL of M NaOH in a constant pressure calorimeter. Initially, both solutions are at 22.5˚C. Find the heat change on a molar basis for the rxn.
NaOH(aq) + HCl(aq) -> NaCl(aq) + H₂O (l)
Qcal (surrounding): qrxn (∆H)(system):
100. mL HCl soln = 100g .05 mols HCl
100 mL NaOH soln = 100 g .05 mols NaOH
s = 4.18 J/g C
Ti: ˚C
Tf: 25.86˚C

17. 2NH₄NO₃(s) -> 2NH₄⁺(aq) + 2NO₃⁻(aq)
Example 2
A 3.53 g sample of ammonium nitrate (NH₄NO₃) was added to 80.0 mL of water in a coffee cup calorimeter. The water temp decreased from 21.6 C to 18.1 C. Find the ∆Hrxn for:
2NH₄NO₃(s) -> 2NH₄⁺(aq) + 2NO₃⁻(aq)
Qcal (surroundings) ∆Hrxn (system)
3.53 g NH₄NO₃ g NH₄NO₃
80.0 mL water = 80.0g
Total mass=83.5g
S= 4.18 J/g C
Ti= 21.6 ˚C
Tf= 18.1 ˚C

18. Classwork Do #54, then 53, which will be a little different
Review sec 6.2 in packet, then work on 39, 41, 43, 49, 51, 57.
Recommended reading: Calorimetry p , then