1. Chapter 11 Thermo chemistry Heat and Chemical Change The Flow of Energy – Heat Measuring and Expressing Heat Changes Heat in Changes of State Calculating Heat Changes

2. Ch 11.1 The Flow of Energy – Heat Energy and Heat Exothermic and Endothermic Processes Heat Capacity and Specific Heat

3. Energy and Heat Thermochemistry – heat changes that occur during chemical reactions Energy – the capacity to do work or supply heat Chemical Potential Energy – energy stored within the structural units of chemical substances

4. Energy and Heat Heat (q) energy that transfers from one object to another because of temperature differences between them Heat flows from a warmer object to a cooler object –Add heat – temperature increases –Give off heat – temperature decreases

5. Exothermic and Endothermic Processes The Law of Conservation of Energy – in any chemical or physical process, energy is neither created nor destroyed All energy in a process can be accounted for as work, stored energy or heat

6. Exothermic and Endothermic Processes Endothermic Processes – a process that absorbs heat from its surroundings, q is positive Exothermic Processes – a process that releases heat to its surroundings, q is negative

7. Heat Capacity and Specific Heat Calorie – quantity of heat needed to raise the temperature of 1g of pure water 1ºC 1 Calorie = 1000 calories = 1kilocalorie Joule (J) = SI unit of heat and energy 1 J = 0.2390 cal 4.184 J = 1 cal

8. Heat Capacity and Specific Heat Heat Capacity – the amount of energy needed to increase the temperature of an object 1ºC –The larger the object, the higher the heat capacity

9. Heat Capacity and Specific Heat Specific Heat Capacity (Specific Heat) – the amount of heat it takes to raise the temperature of 1 g of the substance 1ºC q = mC T

10. Ch 11.2 Measuring and Expressing Heat Changes Calorimetry Thermochemical Equations

11. Calorimetry The accurate and precise measurement of heat change for a chemical or physical processes The heat released by the system is equal to the heat absorbed by the surroundings

12. Calorimetry Calorimeter – insulated device used to measure the absorption or release of heat in a chemical or physical processes

14. Enthalpy (H) The heat content of a system at constant pressure Heat = Enthalpy q = H Therefore: q = H = m C T

15. Thermochemical Equations Heat of Reaction ( H)– the heat change for the equation exactly as written Standard Conditions –101.3kPa (1atm) –25ºC

16. Ch 11.3 Heat in Changes of State Heats of Fusion and Solidification Heats of Vaporization and Condensation Heat of Solution

17. Heats of Fusion and Solidification Molar Heat of Fusion ( H fus ) – the heat absorbed by one mole of a substance melting from a solid to a liquid at a constant temperature Molar Heat of Solidification( H solid ) – the heat absorbed by one mole of a substance solidifying from a liquid to a solid at a constant temperature

18. Heats of Vaporization and Condensation Molar Heat of Vaporization( H vap ) – the heat absorbed by one mole of a substance vaporizing from a liquid to a gas Molar Heat of Condensation( H cond ) – the heat absorbed by one mole of a substance condensating from a gas to a liquid

19. Heat of Solution Molar Heat of Solution ( H soln ) - the heat change caused by one mole of a solute dissolving in a solvent

20. Ch 11.4 Hess’s Law

21. If you add two or more thermochemical equations to give a final equation, then you can also add the heats of reactions to give the final heat of reaction.

22. Example: Diamond to Graphite –C (s, graphite) + O 2 (g)  CO 2 (g)  H = -393.5kJ –C (s, diamond) + O 2 (g)  CO 2 (g)  H = -395.4kJ Reverse the first equation then add both equations together CO 2 (g)  C (s, graphite) + O 2 (g)  H = 393.5k (sign change) C (s, diamond) + O 2 (g)  CO 2 (g)  H = -395.4kJ Final Reaction (add  H) C (s, diamond)  C (s, graphite)  H = -1.9kJ

23. Standard Heats of Formation – (  H 0 f ) The change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states.