CHEM 121 Chapter 7 Winter

Kinetic Molecular Theory of Matter Explains matter in various states

States of Matter Matter: Physical states: 3 Properties of Matter:

Solids Strong attractive forces ( ) Properties: _________________ density _________________ compressibility _________________ shape _________________ thermal expansion 4

Liquids Medium forces ( ) Properties: _________________ density _________________ compressibility _________________ shape _________________ thermal expansion 5

Gases No attractive forces High kinetic E: Properties: _________________ density _________________ compressibility _________________ shape _________________ thermal expansion 6

Measuring Pressure Pressure (P) _1_1/mercury_barometer.html Barometer: 7

Units of Pressure pascal atmosphere Millimeter of mercury psi, pounds per square inch (engineering) 8

Gas Laws 9 4 Variables: P: T: V: n:

Boyle’s Law volume occupied by a gas is __________ related to its pressure 10

A sample of gas has a volume of mL at 1.0 atm. If we increase the pressure to 2.0 atm, what is the new volume of the gas (T is constant)? 11 3-minute practice

Charles’s Law volume of a gas is __________ related to its temperature (K) 12

A sample of gas has a volume of mL at 27 ˚C. If we heat the gas to 54 ˚C (keeping P constant), what is the new volume of the gas? 13 3-minute practice

Gay-Lussac’s Law At constant volume, pressure is __________ related to temperature Combined Gas Law: 14

Avogadro’s Law The volume occupied by a gas is __________ proportional to the amount (mol) of gas (fixed T & P) At fixed T & P: equal volumes of any ideal gas have… 15

Gas Behavior at STP STP: Standard Molar Volume 16

What is the volume (mL) of 0.10 g of helium gas at STP? 17 3-minute practice

Ideal Gas Law Combine: –Boyle’s Law –Charles’s Law –Avogadro’s Law Solve at STP… 18

A tank filled with methane at 23 ˚C and atm is fitted with a safety valve that opens if internal pressure exceeds 1.00 x 10 3 torr. When the tank is placed in boiling water at exactly 100. ˚C, will the safety valve open? Initial: T = P = n = V = Final: T = P = n = V = 19

A sample of gas occupies 105 mL at atm. If temperature remains constant, what is the volume (in L) at 26.4 kPa? Initial: P = V = n = T = Final: P = V = n = T = 20

Each gas in a mixture acts like it is the only gas present Dalton’s Law of Partial Pressures: Mixtures of Gases Example: When water vapor added to pure air…. Each gas exerts __________________________________ 21

Graham’s Law Effusion: gas leak through hole Diffusion: spontaneous mixing of gases 22

Which will deflate more quickly: a balloon filled with helium or nitrogen? 23 3-minute practice

Changes of State 24 Intermolecular Forces:

dipole-dipole polar molecules acting like magnets if between H and N, O, or F _______________ O Intermolecular Forces 25 H H O H H O H H London Dispersion forces

Vapor Pressure As a liquid evaporates: But if closed container… 26 Vapor Pressure:

Boiling As you increase T, vapor pressure _____________ If vapor pressure reaches atmospheric pressure… 27

Sublimation and Melting Solids have vapor pressures too! –Typically low or high? Sublimation: Melting: Decomposition: 28

Heating and Cooling Curves Plateaus: Slopes: 29

Specific Heat (SH) Amount of heat to raise the T of ___ of a substance by ____ 30 How much energy is needed to raise the temperature of 20.0 g of iron by 14.5 °C?

Changes of State Equations Heat of Fusion: Heat of fusion for water = 80 cal / g Heat of Vaporization: Heat of vaporization for water = 540 cal / g 31

Solid State 32

Solid State 33