Ch10.4 Attractive Forces

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1 Ch10.4 Attractive Forces Intermolecular Forces are the forces holding molecules to each other. Solids have strong forces Gases (vapor) have weak forces

2 Intermolecular forces determine the phase of matter.

4 Types: Intermolecular Forces 1. Dipole Dipole Attraction are strong. (ex. Hydrogen bonding) 2. Dispersion forces are weaker (nonpolar)

6 STRONG INTERMOLECULAR FORCES High melting and boiling points Higher molar masses Low vapor pressure Nonvolatile Substances High viscosity High surface tension

7 WEAK INTERMOLECULAR FORCES Low melting and boiling points Lower molar masses High vapor pressure Volatile Substances Low viscosity Low surface tension

8 Solids Definite volume Definite shape Orderly arrangement of particles Particles constantly vibrating

9 Liquids Definite volume no definite shape (takes shape of container) Difficult to compress disorderly arrangement of particles Flowing motion of particles

10 Liquid Properties Viscosity- the resistance of a fluid to flow Thick fluids have high viscosity Ex. Syrup

13 Liquid Properties Surface Tension- Ability of liquid molecules to hold on to each other.

15 Ch Changing States

16 Changes of State Endothermic Process solid liquid Gas/vapor Exothermic Process

17 Melting and Freezing Points Temperature which substances freeze and melt is the same. Each substance has an unique Melting/freezing point

20 Evaporation Conversion of a liquid to a vapor below its boiling point. It occurs only at the surface. Remember the difference between a vapor and gas. Vapor is normally a liquid or solid at room temperature

22 Ch 11.5 Vapor Pressure Vapor pressure measures how easily a liquid changes into vapor Liquids with high vapor pressures turn into vapors very easily. (Volatile liquids) Ex. Gasoline, perfume

23 Dynamic Equilibrium Once equilibrium is reached, the vapor particles will begin to condense back to a liquid at the same rate they change into a vapor.

24 Vapor Equilibrium reached

26 Ch. 10.5, 11.5 Boiling Point The temperature at which the vapor pressure of the liquid equals the atmospheric pressure The entire liquid is changing state, not just the surface. Liquids with low boiling points are considered volatile

28 Difference between Evaporation and Boiling

29 Super Heated Water

30 Ch Condensation The changing of a gas/vapor to a liquid

31 Distillation A method of separating the substances of a mixture with different boiling points. Used in desalinating sea water.

33 Heating/Cooling Curve Used to show how much enthalpy energy (Heat transfer) is needed to change phase. Enthalpy (heat) of Fusion- energy required to change from solid to liquid Enthalpy (heat) of Vaporization- energy required to change from liquid to vapor/gas

34 Enthalpy of Vaporization Enthalpy of Fusion

35 Heating Curve

37 Sublimation Process where solid goes directly to a gas (vapor), because the vapor pressure is so high, liquid phase does not exist. Ex. Iodine, Dry Ice Deposition is a gas back to solid

39 Ch 11.1 Gases Definite volume Definite shape (takes shape and volume of container) Easy to compress Particles are far apart

40 Ch Kinetic Theory of Gases Describe Ideal Gas Behavior 1.Gases consist of tiny particles that move randomly at high velocities. 2.All collisions between gas molecules are perfectly elastic

42 Kinetic Theory of Gases 3.There are no attractive forces between gas particles. 4. The KE of gas molecules is proportional to the Kelvin temperature.

43 Real Gas Behavior At high pressures and low temperatures, gases can not behave ideally. Particles will attract Nonpolar gases, and gases will little mass, almost always behave ideally

45 Temperature The higher the temperature the greater the particle speed. Temperature helps measure kinetic Energy SI base unit is Kelvin (K)

46 Converting from Celsius 0 degree Celsius is equal to 273 K K = 0 C C = K 273 Convert 191 K to Celsius 0 C = = C

49 Ch 11.2 Gas Pressure The result of simultaneous collisions of billions of gas particles with an object. The more collisions, the greater the pressure

52 Vacuum A controlled condition where no gas particles are present. So no gas pressure can exist.

55 Atmospheric Pressure Results from collisions of air molecules with objects. Decreases as you climb a mountain because the air thins out at higher elevations Measured by a barometer

57 Measuring Pressure STP (Standard Temp. Pressure) Standard Temperature at sea level is 0 0 C or 273 K Standard Pressure is kpa, 760 torr, 760 mm Hg, or 1 atm

58 Pressure Conversions How many kpa s are in 1.50 atm? 1 atm = kpa 1.50 atm x 101.3kPa = 152 kpa 1 atm How many kpa s are in 690 mm Hg? 690 mm Hg x kpa = 92 kpa 760 mm Hg

59 Ch 11.3 Gas Relationships Relationships between pressure, volume, temperature and number of moles (amount of particles) While examining relationships, two measurements will always be constant (unchanged)

60 Pressure vs Volume Real Gas

62 Pressure vs Volume Boyle s Law P 1 V 1 =P 2 V 2 For a given mass of gas at a constant temperature, the volume of the gas varies inversely with pressure. Pressure increases, volume decreases Reason:

63 Practice Problem You had a gas that exerted 202 kpa of pressure and took up a space of ml. If you decided to expand the tank to 7.00 L, what would be the new pressure? (Assume constant temperature) P 1 V 1 =P 2 V 2 Check units 202 kpa x liters = P 2 x 7.00 liters 606 kpa L = P 2 x 7.00 liters P 2 = 86.6 kpa

64 Peeps and Boyle s Law

65 BOYLES LAW: DP and DV

66 Ch 11.4 Ideal gas

67 Temperature vs Volume Charles Law- V 1 /T 1 =V 2 /T 2 or V 1 T 2 =V 2 T 1 For a given mass of gas at a constant pressure, the volume of the gas varies directly with its Kelvin temperature. Temperature increases, volume increases Reason:

68 Practice Problem If you took a balloon outside that was at C at 2.0 liters and heated up to C, what volume would the balloon occupy now? (Assume constant pressure) V 1 /T 1 =V 2 /T 2 Check units(remember KELVIN) 2.0 L / 293 K = V 2 / 302 K 604 L K= V 2 V 2 = 2.1 L 293 K

70 FUN WITH ANIMAL BALLOONS

71 Ch.11.5 Temperature vs Pressure Gay-Lussac s Law - P 1 /T 1 =P 2 /T 2 or P 1 T 2 =P 2 T 1 For a given mass of gas at a constant volume, the pressure of a gas varies directly with its Kelvin temperature. Temperature increases, pressure increases Reason:

72 Ostrich Egg in Microwave

73 Ch Combined Gas Law Combines all three gas laws into one expression. (only moles is constant)

74 Practice Problem You have a 2.0 liter balloon that was at C and 1.5 atm. If you take this balloon and place it in a room at STP conditions, what volume would the balloon occupy? P 1 V 1 /T 1 =P 2 V 2 /T 2 (Remember KELVIN) 1.5 atm x 2.0 L / 293 K = 1atm x V 2 / 273 K 819 atm L K = V 2 V 2 = 2.8 L 293 K x 1 atm

75 Ch Avogadro s Law 1 mole of gas at STP= 22.4 liters of any gas Amount (moles) is directly proportional to the space occupied. Density of a gas is measured at STP. Molar mass / molar volume

77 Practice Problem How many liters of Hydrogen gas are in 6.2 grams of hydrogen gas at STP? Molar of mass of is H 2 2 gram/mole 6.2 grams H 2 x 22.4 L H 2 / 2 gram of H 2 69 L of H 2

78 Moles (amount) vs Temp moles increases, temp. decreases Inverse relationship Reason: Ex. Compress tanks become colder as you fill them

79 Ideal Gas

80 Moles (amount) vs pressure moles increases, pressure increases Reason: Ex. Think of a super soaker or simply filling your tire

82 Ch Ideal Gas Law PV = nrt R = constant (L*atm)/(mol*K) 8.31 (L*kPa)/(mol*K)

83 Practice Problem A propane tank holds g of C 3 H 8. How much larger a container would be needed to hold the same amount of propane if the gas is at 25 0 C and a pressure of 3.0 atm?

84 Solution PV=nRT. Check for any units to convert First solve for n g of C 3 H 8. x 1 mole = 44 grams C 3 H moles V*3.0 atm= moles x x298K V = 560 L of propane

85 Practice Problem 2.0 grams of Nitrogen gas is kept under a pressure of 722 torr, and a temperature of C. What is the density of the gas under these conditions?

86 Solution PV=nRT. Convert units first 2.0 g of N 2 x 1 mole = 28 grams N moles 720 torr x 1 atm/760 torr = 0.95 atm V*0.95 atm= moles x x303K = 1.9 L of nitrogen D=m/v D =2.0 g / 1.9 L = 1.1g/L of nitrogen

87 Ch Gas Laws and Reactions Gas Stoichiometry Most check to see if reaction is occurring at STP or not. If not, you most use the Ideal Gas Law Examples on page

88 Ch

89 Dalton s Law Law deals with mixtures of gases. SCUBA tanks

90 LAST LAW! I PROMISE (ch18)

91 Graham s Law of Diffusion Diffusion is the random scattering of gas molecules. The longer they diffuse the more evenly distributed they will become in the container. The heavier the gas the slower the rate of diffusion.

93 Gas Law Review

Ch Kinetic Theory. 1.All matter is made of atoms and molecules that act like tiny particles.

Ch Kinetic Theory. 1.All matter is made of atoms and molecules that act like tiny particles. Ch. 15.1 Kinetic Theory 1.All matter is made of atoms and molecules that act like tiny particles. Kinetic Theory 2.These tiny particles are always in motion. The higher the temperature, the faster the