1. Chapter 6: The States of Matter
Suggested Problems:

2. States of Matter ______ _______ Definite volume and shape
Definite volume but not shape
Takes the shape of its container
_______
No definite volume or shape
Will not only take the shape of its container it will fill it completely

3. Solids A __________ state of matter
Atoms (or molecules) are “touching”
Strongest intermolecular forces
Hold atoms (or molecules or ions, etc.) rigidly in a 3D crystalline lattice

4. Liquids Also a __________ state of matter
Atoms (or molecules) are “touching”
Intermolecular forces hold atoms (or molecules) in contact, but not rigidly in place…molecules can slide past each other

5. Gases Virtually ___ intermolecular forces
Gaseous molecules (etc.) comprise a very small percent of the sample volume
Gaseous molecules are in constant random motion…the velocity is related to temperature
Molecules collide with walls of container and with each other and bounce off with no loss of energy

6. Properties of Gases
Gases are the best understood state of matter, because we ignore intermolecular forces
The volume a gas sample occupies is a function of three variables:
___________

7. Pressure Pressure is force per unit area Units of pressure:
Pounds per square inch
Torr or mmHg
Atmosphere
1 atm = 760 torr = 760 mmHg = 14.7 psi

8. Measuring Pressure: Barometer
gravity pulling down
air pushing down

9. Pressure Conversion Example
The gauge on an oxygen gas cylinder reads 1272 psi. Express this in atm and torr. (1 atm=14.7 psi)

10. Volume of a Gas
Imagine a fixed amount of air at a given temperature and pressure in a balloon
What will happen to the volume if we add more air?

11. Volume of a Gas
Imagine a fixed amount of air at a given temperature and pressure in a balloon
What will happen to the volume if we squeeze the balloon (increase pressure)?

12. Volume of a Gas
Imagine a fixed amount of air at a given temperature and pressure in a balloon
What will happen to the volume if we increase the temperature?

13. The Combined Gas Law P is pressure V is volume
T is ________ temperature
n is number of moles

14. The Empirical Gas Laws Boyle’s Law Charles’s Law Avogadro’s Law
Volume is inversely proportional to pressure (constant n and T)
Charles’s Law
Volume is directly proportional to the Kelvin temperature (constant n and P)
Avogadro’s Law
The volume of a gas is directly proportional to the number of gas moles (constant T and P)

15. Boyle’s Law: Example
15 liters of argon is collected at an initial pressure of 1.05 atm. If the gas is compressed to a new pressure of 1510 torr, what is the new volume?

16. Charles’s Law: Example
The temperature of 35.6 mL of neon is increased from –35.4ºC to 75.2ºC. What is the new volume?

17. Combining Boyle’s and Charles's Laws
A bubble of air having a volume of 75.0 mL is released from 35 feet under the sea (where the pressure is 2.07 atm and the temperature is 18 ºC). What will the new volume be at the surface, where P=0.967 atm and T=23 ºC?

18. The Ideal Gas Law
Combines the elements of the ________ gas laws

19. Standard Conditions STP = standard temperature and pressure
T = _____ K (_____ ºC)
P = _____ atm = ____ torr

20. Example
What volume will 2.0 grams of helium occupy at a temperature of 290K and a pressure of 800 torr?

21. Which Gas Law to Use?
Use the combined gas law when the problem describes two sets of conditions
the pressure and/or temperature changes
Use the ideal gas law when there are a single set of conditions

22. Dalton’s Law of Partial Pressures
The ______ pressure of a gaseous mixture is the sum of the partial pressures
Nitrogen
0.75 atm
Oxygen
0.25 atm
Empty
container
Nitrogen
0.75 atm
Oxygen
0.25 atm
Ptotal =

23. Graham’s Law
__________ is net movement of a gas from an area of high concentration (pressure) to an area of lower concentration
__________ is the movement of a gas through a pinhole
Both Diffusion and Effusion follow Graham’s Law
Rate is an amount per time

24. Graham’s Law Example
Oxygen Molecules weigh 16 times as much as hydrogen molecules. Which molecule will diffuse faster and how much faster?

25. What do all of these changes
Changes of State
Gas
condense
vaporize
sublime
condense
freeze
Liquid
Solid
melt
What do all of these changes
in state have in common?

26. Energy Energy is the ability to do work
Kinetic Energy: energy due to motion
_________ Energy: stored energy
Heat Energy: the sum of the kinetic and potential energies of molecules in a sample

27. Energy and Its Units
calorie (cal): is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius at 15 oC
kilocalorie = 1000 cal
A food Calorie = 1000 cal
Joules (J): are the metric unit of energy
1 cal = J

28. Energy Conversion Example
A candy bar has 350 Calories. How many joules does one candy bar contain?

29. Heat and Temperature
__________: is a measurement of the average kinetic energy of the molecules in a sample
___ is measured in degrees with a thermometer
_______: is the sum of the kinetic (and potential) energies in a sample
_____ is measured in calories with a calorimeter

30. Calorimeters
Bomb Calorimeter
Coffee Cup Calorimeter

31. Specific Heat
Specific heat (SH) is the amount of heat needed to raise the temperature of 1 gram of material by one degree Celsius

32. Specific Heat Example
A 10.0 gram sample of copper at 25 ºC has a final temperature of 100 ºC when 289 J of heat are added. What is the specific heat of copper? (SH of liq water = 4.18 J/goC)

33. Distribution of Energy
In a sample of material, the kinetic energies of the molecules follow a Boltzman Distribution:
Average KE
# Molecules
Kinetic Energy

34. Kinetic Energy Distribution
Thigh
Tlow
# Molecules
Kinetic Energy

35. Changes of State Gas Liquid Solid condense vaporize sublime condense
freeze
Liquid
Solid
melt

36. Vaporization
The most energetic molecules in a liquid have sufficient kinetic energy to escape into the ____ phase
Once the molecules are free as gases, they exert a pressure
This is called the ______ pressure
How does vapor pressure depend on temperature?

37. Vapor Pressure of Water and Ethanol

38. Boiling Point
The boiling point of a liquid is the temperature where the vapor pressure equals the ambient pressure.
The _______ boiling point of a liquid is the temperature where the vapor pressure equals 760 torr.
How does boiling point depend on pressure?

39. What do all of these changes
Changes of State
Gas
condense
vaporize
sublime
condense
freeze
Liquid
Solid
melt
What do all of these changes
in state have in common?

40. Freezing/Melting Point
The melting point of a substance is the temperature at which a crystalline solid changes to a liquid.
What is the difference between melting point and freezing point?

41. Energy Changes and Changes of State
Imagine recording the temperature of an 18 gram (i.e., 1.0 mole) sample of ice at -40ºC as heat is added
heat added, kJ
temperature
0.0
-40
1.5
7.5
15.0
100
55.7
56.5
120
No T
No T

42. Heating Curve for 1 Mole of Water
Water is boiling:
Heat of vaporization
40.7 kJ/mol
Ice is melting:
Heat of fusion
6.02 kJ/mol

43. Molar Heat of Fusion
DHºfus is the heat required to convert one mole of solid to a liquid at at its normal melting point
DHºfus represents the energy needed to break down intermolecular forces and allow molecules to slide around the liquid phase

44. Molar Heat of Vaporization
DH°vap is the heat required to convert one mole of liquid to a gas at at its normal boiling point
DH°vap represents the energy needed to break intermolecular forces and allow molecules to escape into the gas phase

45. Putting it all Together
How much heat is required to convert an 18 gram piece of ice at -40 oC to steam at 120 oC?

46. Heating Curve for 1 Mole of WaterD E
Heat of vaporization
40.7 kJ/mol C
q = m(SH)(T)
SH ice = 2.1 J/goC
SH liq = 4.18 J/goC
SH gas = 2.0 J/goC B
Heat of fusion
6.02 kJ/mol A

47. Question
Explain why orange growers spray their trees with water when there is a threat of freezing temperatures.

48. Question
Why does steam at 100ºC cause more severe burns than water at the same temperature?