1. 5/2 Opener
What is the difference between a dissolution and a chemical reaction?

2. Define Heat Compare Endothermic and Exothermic reactions Know units
Thermochemistry
Define Heat
Compare Endothermic and Exothermic reactions
Know units

3. Energy Transformations
Thermochemistry – the study of energy changes that occur during chemical reactions and changes in state
Chemical potential energy – energy stored in the chemical bonds of a substance

4. Heat
Represented by q
One effect of adding heat to an object in an increase in its temperature
Heat always flows from a warmer object to a cooler object

5. Processes
System – the part of the universe on which you focus your attention
Surroundings – everything else in the universe
Law of Conservation of Energy – in any chemical and physical process, energy is neither created or destroyed

6. Endothermic Process
The system gains heat as the surroundings cool down

7. Exothermic Process
The system loses heat as the surroundings heat up

9. Units for Measuring Heat Flow
Calorie (cal) – the quantity of heat needed to raise the temperature of 1 g of pure water 1°C
Joule (J) – the quantity of heat needed to raise the temperature of 1 g of pure water °C
1J = cal J = 1cal

10. Heat Capacity and Specific Heat
Heat capacity depends on the mass and chemical composition of the object
Specific heat is the amount of heat it takes to raise the temperature of 1g by 1°C
C = q ___ or = ________heat__________
m x ∆T mass(g) x change in °C

11. Plicker Review In what direction does heat flow?
A. Forward B. High to Low C. Low to High D. Up
The part of the universe on which you focus your attention is called:
A. Surroundings B. Earth C. System D. Energy Region
In what process does the system gains heat as the surroundings cool down?
Endothermic B. Caloric C. Exothermic D. Potential
In what process does the system lose heat as the surroundings heat up?
A. Endothermic B. Caloric C. Exothermic D. Potential

12. Ch 17.2 Measuring and Expressing Enthalpy Changes
SWBAT:
Describe Calorimetry
Use Thermochemical Equations

13. Calorimetry
The precise measurement of the heat flow into or out of a system for chemical or physical processes.
Enthalpy (H) of the system is the heat content of a system at constant pressure
A calorimeter is an insulated device used to measure the absorption or release of heat in chemical or physical processes
Constant-Pressure Calorimeters – foam cups which do not let much heat in or out, open to the atmosphere.
Measures enthalpy (H), q = ∆H
qsys = ∆H = -qsurr = -m x C x ∆T
Negative ∆H values are exothermic reactions, while positive ∆H values are endothermic
Constant-Volume Calorimeters, or bomb calorimeter

14. Complete Model 3

15. Enthalpy Calculation
When 25ml of water containing .025mol of HCL at 25*C is added to 25.0 ml of water containing .025mol of NaOH at 25*C in a calorimeter a reaction occurs. Calculate the enthalpy change in joules if the highest temperature observed is 32*C.

16. Thermochemical Equations
In a chemical equation, the enthalpy change for the reaction can be written as either a reactant or a product
A thermochemical equation includes the enthalpy change
The heat of reaction is the enthalpy change for the chemical equation exactly as it is written
The heat of combustion is the heat of reaction for the complete burning of one mole of a substance.

17. Using Heat of Reaction to Calculate Enthalpy Change
2NaHCO3(s) + 129KJ Na2CO3(s)+H2O(g)+ CO2(g) Is this reaction exothermic or endothermic? Calculate the amount of heat required to decompose 2.24 mol NaHCO3.

18. Ch 17.4 Calculating Heats of Reaction

19. Hess’s Law
Hess’s law allows you to determine the heat of reaction indirectly
Hess’s law of heat summation states that if you add two or more thermochemical equations to give a final equation, then you can also add the heats to give a final heat.
Useful in calculating the heat of formation for just one of multiple products

20. Calculating Enthalpy Change
Find the enthalpy change for the conversion of diamond to graphite. C(s, graphite) + O2(g)CO2(g) ΔHf=-393.5KJ C(s, diamond) + O2(g)CO2(g) ΔHf=-395.4KJ
CO2(g) C(s, graphite) + O2(g) ΔHf=393.5KJ
C(s, diamond) + O2(g) CO2(g) ΔHf=-395.4KJ
C(s, diamond) C(s, graphite) ΔHf= -1.9KJ

21. Standard Heats of Formation
The standard heat of formation (∆Hf0) of a compound is the change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states at 25˚C
For a reaction that occurs at standard conditions, you can calculate the heat of reaction by using standard heats of formation
∆H0 = ∆Hf0(products) - ∆Hf0(reactants)

22. Calculating Standard Heat of Reaction
What is the standard heat of the reaction for :
2CO(g) + O2(g)CO2(g)
CO(g) ΔHf=
O2(g) ΔHf= 0
CO2(g) ΔHf=