1. Chapter 10
Energy

2. Energy What is energy? The potential to do work What is work?
Change in self or surroundings
Both work and energy are in units of joules (J)
What are the forms of energy?
Kinetic, Potential, Chemical, Electrical, Nuclear, Sound, Electrochemical, Thermal
What is the formula for nuclear energy?

3. E = m c2

4. Energy calorie The law of conservation of energy
Non-SI unit of energy
1 calorie of energy can raise the temperature of 1 gram of water by 1o C
1 calorie = joules
1 cal = J
1 Calorie = 1kcalories = 1000 calories
The law of conservation of energy
Energy cannot be created out of nothing, but it can be changed from one form to another
Where does electrical energy come from?

6. Thermal Energy What is thermal energy? How is thermal energy measured?
Internal kinetic energy
How fast the particles are moving or vibrating
How is thermal energy measured?
thermometer

7. Heat Heat: transfer of thermal energy
Thermal energy flows from high to low
(high temperature objects transfer thermal energy to objects with lower temperature)
Thermal energy is transferred by conduction, convection or radiation

8. First Law of Thermodynamics
The change in the internal energy of a system is equal to the heat added to the system and the work done on the system
ΔU = q + w

9. Second Law of Thermodynamics
Heat always from high temperature to low temperature.

11. Entropy The state of disorder of the particles.
Particles are more organized at lower temperatures, therefore less entropy
Particles are less organized at higher temperatures, therefore greater entropy
Solids Liquids Gasses

12. Conduction: direct contact

13. Convection: requires a fluid (liquid or gas)

14. Radiation: via electromagnetic waves

15. Radiation: via electromagnetic waves

17. Change in thermal energy
The amount of change in thermal energy can be estimated by determining the change in temperature.
Change in Temp = final temp – initial temp
ΔT = Tf – Ti
also
ΔT = T2 – T1

18. Questions?

19. Check for understanding
1 calorie = _______ joules
A typical 8.0 oz soda could have 110 Calories. That is equivalent to ________ joules.
What is the change in temperature of a soda taken from a refrigerator (at 4o C) and consumed (normal body temp = 37o C)?
In Antarctica, the temperature can drop from a high in the summer of 288 K to a low of 183 K in the winter. Calculate the temp change from summer to winter.
4.184
460000
33o C
-105 K

21. Heat Capacity
When energy is put into or taken away from an object, it can increase or decrease the object’s internal kinetic energy.
Not all objects change temperature at the same rate as energy is added or taken away.

22. Heat Capacity

23. Specific Heat Capacity
The specific heat capacity is the amount of heat per unit mass required to raise the temperature by one degree Celsius. Specific heat can be measured in units of joules per gram oC (J/goC)
q = m x C x ΔT
C is the specific heat, q is the heat required and ΔT is the change in temperature.

24. Heat Capacity
How much energy is absorbed when 88.0 g of water is heated from 5.00o C to 37.0o C? 
q = m x C x ΔT
C (of H2O) = J/ g oC m = 88.0 g C = J / g x C ΔT = 37o C - 5o C = 32o C)
q = (88.0g)( 4.184J/go C)(32oC)
q = 1.18 x 104 J or J

25. Latent Heat
What do you expect to see as you add energy to a substance?

28. Latent Heat
Latent heat is the heat released or absorbed by a chemical substance during a change of state that occurs without a change in temperature
a change of state, e.g. the melting of ice or the boiling of water

29. Heat of Vaporization (ΔHvap)
Problem Solving
Specific Heat (Cp)
Latent
Heat of Fusion (ΔHfus)
Heat of Vaporization (ΔHvap)
Water (H2O)
4.18 J/g °C
334 J/g
2257 J/g
How much heat (energy transfer) is required to melt 100. g of H20? 
Q = m x ΔH
Q = 100g x 334 J/g
= J
= 33.4 kJ

30. Review How is internal kinetic energy measured? Thermometer
What units are used for temperature?
Celsius, Kelvin, Fahrenheit
the transfer of thermal energy is
Heat
What are the units for heat
Joules
What are the units for specific heat?
J/goC

31. Review What is a calorie? Unit of measure for energy & work
The energy required to raise the temp of one gram of water by 1oC
What device did we use in the lab to measure heat?
Calorimeter
How is specific heat calculated?
Heat/(mass x temperature change)

32. Chapter 10 (in a nutshell)
1 cal = ____ joules
4.184
3 Cal = ____ joules
12552.

34. Thermal expansion
In general, if the temperature of a substance increases, so does its volume. This phenomenon is known as thermal expansion.
The notable exception to this rule is water

35. Thermal expansion
The most common thermometers use a glass tube containing a thin column of mercury, colored alcohol, or colored mineral spirits.
When the thermometer is heated, the volume of the liquid expands.
The change in length of the liquid column is proportional to the temperature.

36. Thermal expansion

37. isobaric process
a thermodynamic process in which the pressure stays constant
The addition or removal of energy or any work done on or by the system can alter the total internal energy

38. isobaric process ΔU = q - w
U = internal energy, q = heat, and w = work
If the material is able to expand or contract, work is equal to change in volume, w = p x Δv, where p is pressure and v is volume
Therefore ΔU = q – (p x Δv)

39. Heat Engines
systems that perform the conversion of thermal energy to mechanical work.
A heat source generates thermal energy that brings a substance (e.g. air, water) to a high temperature
The heated substance expands and generates work in the engine and transfers the remaining energy as heat to the colder "sink"

40. Heat Engines

41. Heat Engines
Combustion Engines

42. Heat Engines Combustion Engines

43. Isovolumetric process
Also an isochoric process
A thermodynamic process in which the volume remains constant
Since the volume remains constant, no work can be done by expansion or contraction
Therefore ΔU = q

44. Adiabatic process a process that occurs without the transfer of heat
ΔU = w
w = p x Δv
Therefore ΔU = -(p x Δv)

45. Adiabatic process
Adiabatic heating occurs when the pressure of a gas is increased from work done on it by its surroundings, e.g. compressing a piston
Adiabatic cooling occurs when the pressure of a substance is decreased as it does work on its surroundings.

46. Refrigeration (adiabatic heating and cooling)

47. Air conditioning

48. Santa Ana winds

49. Efficiency of Heat Engines
A measure of how well an engine operates is given by the engine’s efficiency
In general, efficiency is a measure of the useful energy taken out of a process relative to the total energy that is put into the process.

50. Efficiency of Heat Engines
The net work of a heat engine can be calculated by comparing the energy put into the work generating part of the engine to the energy put into the cold sink

51. Efficiency of Heat Engines
The efficiency of the heat engine can be calculated by comparing the net work to the amount of energy that had to be put into the engine to do that amount of work