1. Your Thoughts… Spark 02/22/12
On a very warm day at the beach, which heats up faster, the water or the sand?
Once night rolls in, which cools faster?
If some materials heat up faster than others, although exposed to the same energy, then where does the energy go if something is not getting hotter?
Why might some materials heat up faster than others? How is this transferred energy stored in matter?

2. Matter and Energy Questions
Read the Matter document up to “Temperatures in Kelvin”
What is the KMT?
What is the difference between heat and temperature?
Why is the Kelvin temperature scale used?
How does the K scale convert to Celcius?

3. Enthalpy and Heat
The study of energy and its transformations is known as thermodynamics.
Energy is commonly defined as the capacity to do work or to transfer heat.
Work is energy used to cause an object with mass to move.
Heat is energy used to cause the temperature of an object to increase.

4. Enthalpy and Heat
Kinetic energy is the energy of motion, represented by the equation: Ek = 1/2 mv2 Atoms and molecules have mass and are in motion, therefore they have kinetic energy.

5. Enthalpy and Heat The SI unit for energy is the joule: J = 1 kg-m2/s2
A 2 kg mass moving at 1 m/s possesses a kinetic energy of 1 J:
Ek = 1/2 mv2   = 1/2 (2 kg) (1 m/s)2  
= 1 kg-m2/s2   = 1 J
Since a joule is a small amount of energy, the unit kilojoules, kJ, is often used when describing chemical reactions.

7. Enthalpy and Heat
Traditionally, energy changes in chemical reactions have been expressed in calories, a non-SI unit.
A calorie was originally defined as the amount of heat energy required to raise the temperature of 1 g of water from 14.5 oC to 15.5 oC. It is now defined in terms of the joule:
1 cal = J (exactly)

8. Enthalpy and Heat
A related energy unit used in nutrition is the nutritional Calorie (note the capital letter).
1 Cal = 1000 cal = 1 kcal

9. Heat
Changes

10. Enthalpy

11. E N T H A L P Y - H
heat content in matter:

12. heat content in matter:
E N T H A L P Y - H
heat content in matter:
natural systems tend to go from a state of high energy to a state of low energy.

13. E N T H A L P Y The phases of matter represent "classes" of
molecular motion found
at different temperatures.
Solid
Gas
Liquid

14. X E N T H A L P Y Kinetic Energy The phases of matter
represent "classes" of
molecular motion found
at different temperatures.
Kinetic Energy X

15. X HEAT E N T H A L P Y The phases of matter represent "classes" of
molecular motion found
at different temperatures.
HEAT X

16. E N T H A L P Y q = U + P V q = heat gained or lost
U = internal energy
P = Pressure
V = volume
See Energy notes

17. Hot Coffee Thermal E = 4 Internal E = 2 Solids = 1 Chemical = 0
Liquids = 2
Gases = 3
Chemical = 0

18. Coffee Before Coffee After
Missing 2 units of E: Where did they go?
Total Energy = 5 units
Total Energy = 7 units

19. How can we diagram energy flow when a cup of coffee cools?
Energy Flow Diagram
Is energy flowing in or out of the system?
2 units of energy leave causing the coffee to cool. E E
Cup of Hot Coffee
7 units units = 5 units

20. Spark
Does hot water or cold water freeze faster? Explain using the KMT.
Are you aware of the Mpemba Effect?
What are the four conditions that make the Mpemba Effect possible?(p2-3)
Do you have an explanation for the Mpemba Effect?

21. HMMMM… Can water boil if it’s cold? Explain using the KMT.

22. Heat
Matter does not contain heat, it contains energy (kinetic, thermal, internal energy, chemical energy).
Heat is energy that is transferred from hot to cold
Heat is measured in calories or Joules
1 calorie = J
Measure average kinetic energy with a thermometer and call it temperature
How can we measure heat if things don’t heat and cool the same way?

23. Specific Heat Capacity
Think of it as heating ability…
The amount of heat energy that is required to raise the temperature of one gram of a substance by one degree Celsius is called the specific heat capacity, or simply the specific heat, of that substance.
Water, for instance, has a specific heat of
1.0 calorie per gram degree Celsius [1.0 cal / (g x o C)].
Water becomes our standard for studying energy.

24. Specific Heat Capacity Water
So: It takes 1 calorie of heat to raise 1 gram of water 1 degree How many calories are released if 1 gram of water cools 1 degree? How many calories are needed to heat 1 gram of water at OoC to boiling (100oC)?
1 calorie
100 cal

25. HChemLab
Lab Burners and BTUs

26. BTU Inquiry Lab Tips
Rate of BTU production be lab burner. 1 BTU = Nrg to increase 1 lb of 1oF Convert measurable metric masses and temperatures into BTU’s and predict the time to get a hypothetical rate (BTU/sec)

27. Spark 09/27/2011
How much energy is needed to melt a 10 lb bag of party ice at 0o C? (heat of fusion = 334 J/g or 80 cal/g) There are 2.2 lbs/1 kg
Hfus - heat of fusion
The amount of heat needed to change one gram of a solid into a liquid at its melting point.

28. E N T H A L P Y Hfus - heat of fusion
As energy is added to a solid at its melting point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.

29. E N T H A L P Y Hfus - heat of fusion
The amount of heat needed to change one gram of a solid into a liquid at its melting point.

30. Every phase change is
accompanied by a change
in the energy of the system.

31. As the temperature of a solid
increases, its particle
vibration increases.

32. When a solid melts, its
particles are freed to move
with respect to one another.

33. This melting process
is called fusion.

34. The increased freedom of
motion of the molecules or
ions comes at a price...

35. measured by the
heat of fusion, or
enthalpy of fusion, DHfus

36. solid/liquid phase change
q = m Hfus
q = heat gained or lost
m = mass
DHfus = heat of fusion

37. Hfus H2O = 334 J/g Hfus lead = 24.72 J/g
E N T H A L P Y
Hfus H2O = 334 J/g
Hfus lead = J/g

39. As the temperature of a liquid
increases, the molecules move
with increasing energy.

40. When increasing temperature,
the concentration of gas-phase
molecules just above the
surface of the liquid increases.

41. These gas-phase molecules
exert a pressure on the
liquid called vapor pressure.

42. This vapor pressure
increases with temperature
until it equals the
atmospheric pressure.

43. This is the boiling
point of the liquid.

44. The energy required to
cause this transition..

45. is called the heat of
vaporization or enthalpy
of vaporization, DHvap

46. E N T H A L P Y
As energy is added to a liquid at its boiling point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.

47. Hvap - heat of vaporization
E N T H A L P Y
Hvap - heat of vaporization
The amount of heat needed to change one gram of a liquid into a gas at its boiling point.

48. liquid/gas phase change
q = m Hvap
q = heat gained or lost
m = mass
DHvap = heat of vaporization

49. E N T H A L P Y
Hvap H2O = 2260 J/g

51. is used to measure heat change
A Calorimeter
is used to
measure
heat change

52. Lab
Heat of Fusion of Ice

53. Spark q = m x ΔT x s
50.0 grams of hot water (65.0oC) are added to a calorimeter that has 25.0 grams of water at 5.0oC. After mixing the final temperature reached was 44.0oC. 1 cal = J = E to raise 1 g H2O 1oC How much energy was released from the hot water? How much was absorbed by the cold water? Is energy being conserved? Does the nrg released = the nrg absobed?

54. Lab
Calorimeter Constant

55. Lab
Heat of Solutions and Reactions

56. Spark
With your group, calculate your mean calorimeter constant. Send a representative to me with your value for spreadsheet credit. Be sure that all group members know what the calorimeter constant reflects!

57. Specific Heat Capacity
What is
Specific Heat Capacity
How “well” a substance heats up…
How much energy is needed to heat something up…

58. Specific Heat Capacity
The heat required to raise
the temperature of one
gram of a substance by
one Celsius degree.

59. change temp within phase
q = m T Cp
q = heat gained or lost
m = mass
DT = “change in temperature”
Cp = specific heat capacity

60. Specific Heat Capacity
The amount of heat energy involved in changing the temperature of a sample of a particular substance depends on three parameters -- the specific heat of the substance, the mass of the sample, and the magnitude of the temperature change.
The Greek letter delta (Δ) is used to indicate a change.
Δ T = temperature final - temperature initial

61. The General Idea Behind Specific Heat Labs
Both ice or a heated sample will be placed into a crude calorimeter, consisting of water contained in a plastic foam cup. Shortly after mixing, the sample will have come to the same temperature as the water or the water temperature will increase or decrease depending on the change.
Because Styrofoam is a good insulator, heat cannot easily escape from the calorimeter to the surroundings.

62. Specific Heat Labs
The heat lost or gained by the sample should be equal to the heat gained or lost by the water.
The amount of heat energy gained by the water will be calculated in the following manner:
heat gained water = specific heat water X mass water X ΔTwater

63. The heat lost by the sample is given by a similar equation:
heat lostsample = specific heat sample X mass sample X ΔTsample
Because the heat gained must equal the heat lost, a third equation can be written:
specific heat water X mass water X ΔT water = specific heat sample X mass sample X ΔT sample

64. The specific heat of water is known.
The temperature changes of the water, and of the sample, can be measured, as can the mass of the water and the mass of the sample.
Using this data, the specific heat of the sample can be calculated.
Calorimetry values are all determined based on the temperature changes of the water sample.

65. Specific Heat Capacity
Which has the greater?
Specific Heat Capacity
H2O Cu or

66. Specific Heat Capacity
Cp of ice = 2.06 J/g.Co
Cp of water = 4.18 J/g.Co
Cp of steam = 2.02 J/g.Co
Cp of copper = .385 J/g.Co

67. q=mTCp - change temp q=mHvap q=mTCp - change temp q=mHFUS- change
change phase
q=mTCp - change temp
q=mHFUS- change
phase
q=mTCp - change temp

68. How much heat is needed to convert 250 grams of ice at
-30 oC to vapor at 150 oC?
Change temp of ice
Melt ice
Change temp of liquid water
Vaporize water
Change temp of vapor
Add total heat used

69. Step raise temp of ice
q = m DT Cp
q = (250g) (30 Co) (2.06 J/g. Co)
q = 15,450 Joules

70. Step 2 melt ice q = m DHfus q = (250g) (334 J/g) q = 83,500 Joules

71. Step 3 raise temp of liquid water
q = m DT Cp
q = (250g) (100 Co) (4.18 J/g. Co)
q = 104,500 Joules

72. Step 4 vaporize liquid water
q = m DHvap
q = (250g) (2260 J/g)
q = 565,000 Joules

73. Step 5 raise temp of water vapor
q = m DT Cp
q = (250g) (50 Co) (2.02 J/g. Co)
q = 25,250 Joules

74. Step 6
q = 15,450
83,500
104,500
565,000
25,250
q = 794,000 Joules

75. Lab
Specific Heat of a Metal

76. Lab
Heat of Combustion of Wax

77. Spark
Get your materials for the specific heat lab. 3 groups may use burners otherwise use a hot plate. Use 2 foam cups instead of one Calorimeter water should be cold. I will give you your metals once you have everything else.

78. Enthalpy
end

79. Phase Diagram

80. P h a s e D i a g r a m
A g r a p h s h o w i n g t h e p h a s e s o f m a t t e r a s t h e y r e l a t e t o t e m p e r a t u r e a n d p r e s s u r e .

82. M a j o r p o i n t s o n a p h a s e d i a g r a m
Normal Atmospheric Pressure
Triple point
Boiling Point
Melting point
Critical temperature

84. kPa
normal atmospheric pressure

86. TP
Triple Point

88. Tb
Normal
boiling point

90. Tm
Normal
melting point

92. Tc
Critical
temperature

93. V a n d e r W a l l s A t t r a c t i o n
T h e f o r c e o f a t t r a c t i o n b e t w e e n
m o l e c u l e s

94. Nineteenth Lab
Calories in a Peanut

95. Phase Diagram
end