1. Goals This should all be review for you from unit one …
You should be able to describe 3 states of matter
You should be able to explain the difference between temperature and heat

2. What is matter? What is matter made of?
The stuff that makes up all things
What is matter made of?
Atoms, molecules, particles that are always moving

3. Intermolecular Forces
Inter- between or among
Molecular- refers to molecules (which are the building blocks of all things!)
Intermolecular forces = forces between molecules

4. States or Phases of Matter
Solid
Energy of Molecules: Little, not a lot
Intermolecular Forces: STRONG! (keep it together!)
Volume: Definite (cannot be changed)
Shape: Definite (cannot be changed)

5. States or Phases of Matter
Liquid
Energy of Molecules: Medium, more than solid
Intermolecular Forces: Not as strong
Volume: Definite (cannot be changed)
Shape: Not definite (can be changed)

6. States or Phases of Matter
Gas
Energy of Molecules: Lots!
Intermolecular Forces: Weak (don’t really need to be held together)
Volume: Not definite (can be changed)
Shape: Not definite (can be changed)

7. States Of Matter
What do they look like on a molecular level?

8. States or Phases of Matter
Plasma
We don’t know much about it
Found in space
NOT the same as plasma in TVs

9. Q: How does matter go from one state to another?
Solid  Liquid
Energy: Added
Called: Melting
Example:

10. Q: How does matter go from one state to another?
Liquid  Gas
Energy: Added
Called: Vaporization (boiling or evaporation)
Example:

11. Q: How does matter go from one state to another?
Liquid  Solid
Energy: Removed
Called: Freezing
Example:

12. Q: How does matter go from one state to another?
Gas  Liquid
Energy: Removed
Called: Condensation
Example:

13. Q: How does matter go from one state to another?
Solid  Gas (no stop at liquid)
Energy: Added
Called: Sublimation
Example:

14. Q: How does matter go from one state to another?
Gas  Solid (no stop at liquid)
Energy: removed
Called: deposition
Example:

15. Eureka Movies Eureka: Molecules in a Solid
Eureka: Evaporation & Condensation
Eureka: Molecules in a Liquid
Eureka: Expansion & Contraction

16. Q: What is a phase change diagram?
Shows the temperatures at which different changes of phase take place
Also shows how much energy is required to make certain changes in phase occur

17. Phase Change Diagram Gas Condensation Vaporization Freezing Liquid
Melting
Solid

18. Q: What do you need for a change of phase?
Energy
- Energy must be transferred in order for a phase change to occur!

19. Q: What do you need for a change of phase?
Heat of vaporization-
- the amount of energy needed to change something from l  g or g  l (amount of energy to turn something into a VAPOR)
Heat of fusion-
- the amount of energy needed to change something from s  l and l  s

20. Q: Compare and Contrast evaporation and boiling.
- Both are change from liquid to gas
- Both are COOLING processes (occur in order to cool something off)
*Think of when you sweat!*

21. Q: Compare and Contrast evaporation and boiling.
- Boiling occurs throughout the liquid AND at the surface; evaporation occurs only at the surface of a liquid
- Boiling can only happen when there is correct pressure from the surrounding atmosphere; evaporation isn’t affected by pressure

22. Eureka: Measuring Temperature
Eureka: Temperature vs Heat
Eureka: Heat as Energy

23. Q: What does this have to do with energy transfer or heat flow?
Energy can be transferred when….
Molecules bump into each other
Hotter, FASTER molecules bump into cooler, SLOWER molecules
Energy lost by one object is equal to energy gained by the other object (1st law of thermodynamics)
As a result, the cooler molecules speed up and become warmer
Energy never moves cold to hot!!!
2nd law of thermodynamics

24. Temperature Measure of the AVERAGE kinetic energy in a substance
Does not depend on the number of molecules/particles
If we add all KE for all molecules, and divide by the total number of molecules, that will tell us the temperature
Measured in degrees (F, C, K= Kelvin)

25. Heat
Measure of the movement of thermal energy from one object to another (thermal energy - total potential and kinetic energy in an object)
Depends on number of molecules/particles
More particles means more thermal energy
there can be more movement of energy
there is more heat
Thermal energy flows from something with more energy (hotter) to something with less energy (cooler)
Measured in JOULES or Calories

26. Q: How fast can thermal energy move to cause heat?
Rate of thermal energy being transferred is determined by two things:
Separation of molecules
Freedom of molecules to move

27. So, which state of matter is best for energy transfer?
Solid
Separation: Little
Freedom: Little
Energy Transfer: Great (molecules can bump into each other easily!)

28. So, which state of matter is best for energy transfer?
Liquid
Separation: Medium
Freedom: Medium
Energy Transfer: Ok (molecules can bump into each other sometimes)

29. So, which state of matter is best for energy transfer?
Gas
Separation: Lots
Freedom: Lots
Energy Transfer: Bad (molecules don’t bump into each other a whole lot)

30. Q: What does all of this have to do with temperature and heat?
Temperature is a measure of AVERAGE kinetic energy
To cause heat and to measure temperature, thermal energy flows between a substance and the thermometer (this causes the material inside the thermometer to EXPAND)
Thermal energy flows until “thermal equilibrium” is reached

31. Q: What does all of this have to do with temperature and heat?
Thermal Equilibrium-
Equal movement of thermal energy from one substance to the other
If 100 J of energy leaves substance, 100 J will enter from surroundings
“give and take”

32. Q: What does all of this have to do with temperature and heat?
When the temperature of a PHASE CHANGE is reached, the substance will remain at that temperature until all energy is used to make the phase change occur
Intermolecular forces need to be broken or put back in…

33. Energy in Reactions
Exothermic reactions: release heat; feels hot to the touch
Endothermic reactions: absorb heat; feels cool to the touch

34. Limits on Temperature Upper limit: none
Lower limit: -273 C or 0 K (called absolute zero)
At this point, molecules have no energy, so no movement (not possible!)
Third Law of Thermodynamics
Kelvin Scale: another temp scale, based on absolute zero being coldest temperature, 1 Kelvin degree = 1 Celsius degree

35. What is cold?
Not a lot of kinetic energy so you will not be able to transfer energy (heat) to an object around you

36. Eureka
Conduction
Convection
Radiation Waves

37. Q: What are some ways heat energy can be transferred from one place to another?
Conduction
Occurs when particles collide (bump) with each other
- Generally occurs with solids

38. Q: What are some ways heat energy can be transferred from one place to another?
Good conductors
Have “free electrons” that are able to jump around like in a pinball machine
- Things that are metals: silver, iron, aluminum, etc

39. Q: What are some ways heat energy can be transferred from one place to another?
Bad conductors
- Called insulators (they actually hold on to energy, don’t pass it around)
Air is a bad conductor, so insulation has lots of AIR in it
Things like: wood, Styrofoam, wool, water (within a container), etc

40. Q: What are some ways heat energy can be transferred from one place to another?
Convection
- Occurs in fluids (gases and liquids)

41. Convection Continued…
Fluid is heated from below and the molecules on the bottom start moving faster.
The molecules on the bottom spread apart and become less dense.
The less dense molecules move up to the top, as the denser, cooler fluid moves to the bottom
This creates “convection currents”.
(The warmer fluid will always move away from the heat source and the colder will move towards it.)

43. Convection Continued…
Gases will rise until they reach the air with the same density
- When air expands, it cools.
- When air is compressed (pushed together), it heats

44. Q: What are some ways heat energy can be transferred from one place to another?
Radiation
Occurs when electromagnetic waves travel through space
These waves travel through “nothingness”
- Ex. Sun heats the planet in this way

45. Emission of Radiant Energy
The effects of radiation increase with larger size and closer range.
Earth also emits radiant energy (called terrestrial radiation)

46. Absorption of Radiant Energy
Good emitters are good absorbers & bad emitters are bad absorbers
Dark objects absorb and emit radiation better than lighter objects (which is why dark things heat up and cool off faster than light things)

47. Q: What are some ways heat energy can be transferred from one place to another?
Convection
- Occurs in fluids (gases and liquids)

48. Convection Continued…
Fluid is heated from below and the molecules on the bottom start moving faster.
The molecules on the bottom spread apart and become less dense.
The less dense molecules move up to the top, as the denser, cooler fluid moves to the bottom
This creates “convection currents”.
(The warmer fluid will always move away from the heat source and the colder will move towards it.)

50. Convection Continued…
Gases will rise until they reach the air with the same density
- When air expands, it cools.
- When air is compressed (pushed together), it heats

51. Q: What are some ways heat energy can be transferred from one place to another?
Radiation
Occurs when electromagnetic waves travel through space
These waves travel through “nothingness”
- Ex. Sun heats the planet in this way

52. Emission of Radiant Energy
The effects of radiation increase with larger size and closer range.
Earth also emits radiant energy (called terrestrial radiation)

53. Absorption of Radiant Energy
Good emitters are good absorbers & bad emitters are bad absorbers
Dark objects absorb and emit radiation better than lighter objects (which is why dark things heat up and cool off faster than light things)

54. Q: Why is water such a special chemical?
In this unit, one important thing we need to know about water is its specific heat.
- Specific heat capacity- tells us how likely something is to gain/hold or lose heat. (how much heat energy does it take to raise the temperature of 1 g by 1 oC)

55. Specific Heat
High specific heat capacity- it takes LOTS of energy to increase the temp and LOTS of energy has to be lost in order for temp to decrease.
(ex. Water- takes a long time to heat up and cool down, lots of energy req’d and lots of energy lost)

56. Specific Heat
Low specific heat capacity- it doesn’t take a whole lot of energy to increase the temp and not a lot of energy has to be lost in order to decrease the temp
(ex. Sand- doesn’t take too long to heat up and cool down, desert sand gets hot fast and cools fast)

57. Q: Why is water such a special chemical?
Another important characteristic of water is the fact that it EXPANDS when it gets cold really cold
At 4°C, water is at its most dense (has smallest volume).

58. Q: Why is water such a special chemical?
This is why ice floats.
If water behaved like other substances, ice would become too dense to float.
Particles are all crammed together, no empty space to allow buoyancy (floating)

59. Practice Problem #1
A 445 g sample of ice at –58oC is heated until its temperature reaches –29oC. Find the change in heat content of the system (c for ice = 2.03 J/goC)
26, 197 J

60. Practice Problem #2 .61 J/g°C
What is the specific heat of an unknown element (in J/g°C) if it takes 190 J to raise the temperature of 52.0g by 6.0oC?
.61 J/g°C

61. Practice Problem #3 .52 J/g°C
What is the specific heat of titanium (in J/g°C)if it takes 89.7 J to raise the temperature of a 33.0g block by 5.20°C?
.52 J/g°C

62. Practice Problem #4 1.45 J/g°C
What is the specific heat of an unknown element (in J/g°C) if it takes 210 J to raise the temperature of 63.0g by 2.3oC?
1.45 J/g°C

64. Answers 1) Sublimation 2) Melting 3) Vaporization 4) Freezing
5) Condensation
6) Deposition

65. How much heat is absorbed when 500 g of water goes from 25 ⁰C to 35 ⁰C
How much heat is absorbed when 500 g of water goes from 25 ⁰C to 35 ⁰C? (Cp of water (l) = 4.18 J/g⁰C)
20,920 J

66. A 445 g sample of ice at –58oC is heated until its temperature reaches –29oC. Find the change in heat content of the system (c for ice = 2.03 J/goC)
26, 197 J

67. What is the specific heat of an unknown element (in J/g°C) if it takes 190 J to raise the temperature of 52.0g by 6.0oC?
.61 J/g°C

68. What is the specific heat of titanium (in J/g°C)if it takes 89
What is the specific heat of titanium (in J/g°C)if it takes 89.7 J to raise the temperature of a 33.0g block by 5.20°C?
.52 J/g°C

69. Concepts… Heat of vaporization Heat of fusion Thermal energy
Specific Heat
Thermal equilibrium
Absolute zero