Behaviors of Solids, Liquids, and Gases Source Behaviors of Solids, Liquids, and Gases Video 1 Video 2 LO 2.3: The student is able to use particulate models to reason about observed differences between solid and liquid phases and among solid and liquid materials.

Properties of Gases Gases expand to fill any container. random motion, no attraction Gases are fluids (like liquids). particles flow easily Gases have very low densities. lots of empty space; particles spaced far apart Gases are easily compressible. empty space reduced to smaller volume Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Kinetic Molecular Theory (KMT) Source Kinetic Molecular Theory (KMT) Video 1 Video 2 IF the temperature is not changed, no matter what else is listed in the problem, the average kinetic energy of a gas does not change. That is the definition of temperature! All gases begin to act non-ideally (aka real) when they are at low temperatures and/or high pressures because these conditions increase particle interactions Under the same conditions, the stronger the intermolecular attractions between gas particles, the LESS ideal the behavior of the gas LO 2.4: The student is able to use KMT and IMF’s to make predictions about the macroscopic properties of gases, including both ideal and non-ideal behaviors

Properties of a Gas - Factors Source Properties of a Gas - Factors Don’t worry about individual gas law names, but do worry about the effect of changing moles, pressure and temperature on a sample of gas Virtual Lab LO 2.5: Refine multiple representations of a sample of matter in the gas phase to accurately represent the effect of changes in macroscopic properties on the sample

Pressure = Force/Area KEY UNITS AT SEA LEVEL (also known as standard pressure) 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi Sea level

Standard Temperature & Pressure STP STP Standard Temperature & Pressure 0°C 273 K 1 atm 101.325 kPa - OR -

Combined Gas Law P1V1 T1 = P2V2 T2 P1V1T2 = P2V2T1

Molar Volume (Avogadro) 1 mol of all gases @ STP have a volume of 22.4 L Avogadro’s Law V1/n1 = V2/n2 MOLAR VOLUME One mole of any gas occupies 22.4 liters at standard temperature and pressure (STP).

PV = nRT Ideal Gas Law Brings together all gas properties. P = pressure V = volume (must be in liters) n = moles R = universal gas constant (0.082 or 8.314) T = temperature (must be in Kelvin) Can be derived from experiment and theory.

Ptotal = P1 + P2 + ... Dalton’s Law The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases. Ptotal = P1 + P2 + ... In a gaseous mixture, a gas’s partial pressure is the one the gas would exert if it were by itself in the container. The mole ratio in a mixture of gases determines each gas’s partial pressure.

Gas Mixtures and Dalton’s Law

Gas Collected Over Water When a H2 gas is collected by water displacement, the gas in the collection bottle is actually a mixture of H2 and water vapor.

D = (MM)P/RT Gas Density Larger particles are more dense. Gases are more dense at higher pressures and lower temperatures D = density P = pressure MM = molar mass R = universal gas constant T = temperature (must be in Kelvin) Can be derived from experiment and theory.

Click reveals answer and explanation. Source The Ideal Gas Law Video LO 2.6: The student can apply mathematical relationships or estimation to determine macroscopic variables for ideal gases Click reveals answer and explanation.

Deviations from Ideal Gas Behavior Source Deviations from Ideal Gas Behavior Video When watching the video, don’t concern yourself with Van der Walls – AP Exam focuses on LDF’s instead Click reveals answer and explanation. LO 2.12: The student can qualitatively analyze data regarding real gases to identify deviations from ideal behavior and relate these to molecular interactions