CHEM 121 Chapter 7 Winter 2015

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

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

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

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

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

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

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

3-minute practice A sample of gas has a volume of 100.0 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)?

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

3-minute practice A sample of gas has a volume of 100.0 mL at 27 ˚C. If we heat the gas to 54 ˚C (keeping P constant), what is the new volume of the gas?

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

Avogadro’s Law At fixed T & P: equal volumes of any ideal gas have… 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…

Gas Behavior at STP STP: Standard Molar Volume

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

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

A tank filled with methane at 23 ˚C and 0 A tank filled with methane at 23 ˚C and 0.991 atm is fitted with a safety valve that opens if internal pressure exceeds 1.00 x 103 torr. When the tank is placed in boiling water at exactly 100. ˚C, will the safety valve open?

A sample of gas occupies 105 mL at 0. 903 atm A sample of gas occupies 105 mL at 0.903 atm. If temperature remains constant, what is the volume (in L) at 26.4 kPa?

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

Changes of State Intermolecular Forces:

Intermolecular Forces dipole-dipole polar molecules acting like magnets if between H and N, O, or F _______________ H O H H O O H H H All intermolecular forces are weaker than bonds (ionic, covalent, metallic) London Dispersion forces

Vapor Pressure As a liquid evaporates: Vapor Pressure: But if closed container… Stronger intermolecular forces  lower vap pressure Vapor Pressure:

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

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

Heating and Cooling Curves Plateaus: Slopes:

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