1. Energy and Heat Curves
Chapter 6 part 1

2. Thermodynamics No work work The science of heat and work
Energy is the “ability to do work” or supply heat
No work
Energy makes things happen
Can’t see energy or directly measure energy
All chemical reactions (rx) involve energy changes
Energy is released or absorbed depending on the balance between the bonds broken/formed
Energy is absorbed to break bonds
Energy is released to form bonds
work

3. Forms of Energy Potential - stored energy
Gravitational - due to position
Chemical - energy stored in bonds
Electrostatic - b/w + and - ions

4. Forms of Energy KINETIC ENERGY Energy due to motion
Thermal - molecular motion
Mechanical - an object’s motion
Electrical
Sound

5. Units of Energy
calorie or cal
Joule or J
1 cal = J

6. First Law of Thermodynamics
Conservation of Energy
Energy cannot be created nor destroyed; it just changes form

7. How we look at reactions
System - substances undergoing a change
Surroundings - everything else not part of system

8. Heat, q
Transfer of thermal energy b/w the system & surroundings from high to low temps

9. Exothermic and Endothermic
Heat is absorbed by a substance
Sign: positive
Heat is released from a substance
Sign: negative
Overall energy is conserved!

10. Calorimetry The study of heat transfer b/w system and surroundings
Heat Curve for a Substance T
(°C)
Occurs for any substance
As energy is added a substance warms up, or melts/vaporizes
As energy is removed (cooling curve) from a substance it cools down, freezes/condenses
Heat transfer depends on
1) mass (m); g
2) size of T change (∆T);
3) Specific heat of material (C); J/ g K
Heat added

11. Heat Curves
During a temp change the kinetic energy of a substance increases/decreases
q = mC∆T
During a phase change the potential energy of a substance increases/decreases

12. Phase Changes Heat of fusion or ∆Hfus q supplied (+) for s --> l
q released (-) for l --> s
Heat of vaporization or ∆Hvap
q supplied (+) for l --> g
q released (-) for g --> l
Use ∆Hfus and ∆Hvap as conversions

13. Page 6-3 and 6-4
Energy Problems