Unit 7 States of matter and the Behavior of Gases Chemistry Chapter 13 & 14

Goal 1: States of Matter and Vocabulary Attractive Forces Forces between particles of a substance. Intermolecular Forces. Hold particles together. Kinetic Energy Energy of Motion. Related to mass and speed of particles KE = ½ mv2 Temperature Measure of Average Kinetic Energy of a sample. As temperature increases, particles move faster in a sample Collisions Collisions between atoms and molecules are ELASTIC. This means Kinetic Energy is conserved. TEMPERATURE is NOT lost due to Collisions. Collisions result in PRESSURE.

States of Matter SOLID LIQUID GAS Attractive Forces between Particles Strong Weaker Virtually Nonexistent Volume & Compressibility Definite Volume Not Compressible Indefinite Volume Compressible Molecular Motion Low Small distance between Medium High Large distance between

Goal 2: Kinetic Molecular Theory Describes the MOTION of gas particles 3 Statements of the Theory The particles in a gas are considered to be small, hard spheres with an insignificant volume: NO attractive or repulsive forces exist between them. The particles of a gas travel in rapid, constant, and random motion. They travel in straight line paths that are independent of each other. All collisions between particles are perfectly elastic (no kinetic energy is lost). The total kinetic energy of the gas particles remains constant.

Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE. Gas Pressure Number of collisions that take place. More collisions = More pressure.

Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE. Number of collisions that take place. More collisions = More pressure. Volume Space that particles take up. Particles will completely fill a container with their random motion.

Kinetic Energy and Temperature Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE. Pressure Number of collisions that take place. More collisions = More pressure. Volume Space that particles take up. Particles will completely fill a container with their random motion. Kinetic Energy and Temperature Average Kinetic Energy of Particles Related to speed of particles. Greater Speed = Greater Temperature.

Kinetic Molecular Theory Simulations http://chemconnections.org/Java/molecules/ http://www.chm.davidson.edu/ChemistryApplets/KineticMolecularTheory/BasicConcepts.html http://www.chm.davidson.edu/ChemistryApplets/KineticMolecularTheory/Maxwell.html

Temperature Theory: Kelvin Scale Volume Temperature What is absolute 0? How was 0K found? Why use Kelvin?

The Nature of Liquids Goal 3: Attractive Force Affects

Vapor Pressure The pressure caused by evaporated gas particles pushing down upon a liquid Stronger attractive forces result in lower Vapor pressures At higher temperatures vapor pressure increases More molecules evaporate at higher temperatures Water: Low vapor pressure Chart on page 427(WATER) Temp. V. Pressure 20°C 2.33kPa 60°C 19.92kPa 100°C 101.3kPa

Vapor pressure of substance

Boiling Point Temperature at which vapor pressure equals external pressure. The liquid goes beyond just evaporation at Boiling Point. Gas bubbles begin to form throughout the liquid. Stronger attractive forces result in higher BP’s

Volatility Likelihood of a liquid evaporating. High Volatility: Liquid has high vapor pressure Liquid is more likely to evaporate – produce more vapor High Volatility: Liquids with weaker attractive forces Water: Low volatility

Surface Tension Inward force (pull) between the molecules of a liquid. High Surface Tension: Holds a liquid into drops Liquids with very strong attractive forces have greater surface tension Water: High surface tension

Goal 4: Phase Diagrams Triple Point Page 438“Phase Diagram Temperature and Pressure in which ALL THREE phases can exist. Page 438“Phase Diagram

Goal 5: Gas Variables 4 variables define a gas system Pressure: (P) Units: Pascal (Pa) Atmospheres (atm) Millimeters of Mercury (mm Hg) 1 atm = 101.3 kPa = 760 mm Hg Volume: (V) Liters (L), milliliters (mL), (cm3) Temperature: (T) Celsius (°C) Kevin (K) Kelvin is the Official Unit Kelvin must be used in calculations Number of Particles: (n) Unit: Moles (mol)

Stoichiometry Review At STP: 1mol = 22.4L Review STP: Standard Temperature and Pressure 1 atm (101.3 kPa) 0°C (273 K) Review 1 mol = molar mass 1 mol = 6.02 x 1023 particles 1 mol = 22.4L (at STP)

Stoichiometry Examples Li3N(g) + 3H2O(l)  NH3(g) + 3LiOH(aq) What mass of water is needed to react with 29.3 L of Li3N? When 13.3 L of NH3 are produced how many formula units of LiOH are produced? Given 7.8 moles of LiOH produced, what volume of Li3N was used?

Math Review Direct Relationship (between X & Y) Generic Equation Y = kX (k is a constant) k = Y/X Graph Y vs. X will be a LINE (k is the SLOPE) Inverse Relationship (between X & Y) Y = k/X (k is a constant) k = XY Y vs. X will be a HYPERBOLA

Goal 6: Gas Laws

Boyle’s Law At constant TEMPERATURE: Pressure and Volume are INVERSE PV = constant P1V1 = P2V2 Graph of P vs. V: As Pressure increases  Volume ___________

Boyle’s Law At constant TEMPERATURE: Pressure and Volume are INVERSE PV = constant P1V1 = P2V2 Graph of P vs. V: As Pressure increases  Volume _decreases _

Sample Problem 14.1 A balloon contains 30.0 L of helium has at 103 kPa. What is the volume of the helium when the balloon rises to an altitude where the pressure is only 25.0 kPa? (Assume that the temperature remains constant

Charles’ Law At constant PRESSURE: Temperature and Volume are DIRECT V/T = constant Graph of V vs. T: As Temperature increases  Volume __________

Charles’ Law At constant PRESSURE: Temperature and Volume are DIRECT V/T = constant Graph of V vs. T: As Temperature increases  Volume _increases_

Sample Problem 14.2 A balloon inflated in a room at 24⁰C has a volume of 4.00 L. The balloon is then heated to a temperature of 58⁰C. What is the new volume if the pressure remains the same?

Gay-Lussac’s Law At constant VOLUME: Temperature and Pressure are DIRECT P/T = constant Graph of P vs. T: As Temperature increases  Pressure _________

Gay-Lussac’s Law At constant VOLUME: Temperature and Pressure are DIRECT P/T = constant Graph of P vs. T: As Temperature increases  Pressure increases_

Sample Problem 14.3 Aerosol cans carry labels warning not to incinerate (burn) the cans or store them above a certain temperature. This problem will show why it is dangerous to dispose of aerosol cans in a fire. The gas in a used aerosol can is at a pressure of 103 kPa at 25⁰C. If the can is thrown onto a fire, what will the pressure be when the temperature reaches 928⁰/C?

Combined Gas Law All 3 laws put together k = constant

Sample Problem 14.4 The volume of a gas-filled balloon is 30.0 L at 313 K and 153 kPa pressure. What would the volume be at STP?

Gas Law Simulations http://phet.colorado.edu/simulations/sims.php?sim=Gas_Properties

Ideal Gas Law P: Pressure V: Volume T: Temperature n: Number of Moles or P: Pressure V: Volume T: Temperature n: Number of Moles R: Ideal Gas Law CONSTANT R = 8.31 (kPa∙L)/(K∙mol)

Sample Problem 14.5 At 34⁰C, the pressure inside a nitrogen-filled tennis ball with a volume of 0.148 L is 212 kPa. How many moles of nitrogen gas are in the tennis ball?

Special Problem: What is the volume of 1 mol of a gas at STP?

Goal 7: Dalton’s Law The total pressure of a gas mixture is the “sum” of the pressures of each individual gas in the mixture Pt = P1+P2+P3… Each gas pressure depends on its abundance Mole Fraction or Abundance “think percent as decimal”

Atmosphere TOTAL NITROGEN 78% OXYGEN 21% OTHERS 1% If total pressure is 1 atm and they all have the same volume, calculate each partial pressure: Nitrogen’s Pressure = (.78)(1 atm) = .78 atm Oxygen’s Pressure = (.21)(1 atm) = .21 atm Others Pressure = (.01)(1 atm) = .01 atm

Dalton Law Examples A container has a mixture of atmosphere and water vapor. At 50°C the partial pressure of water vapor is 12.34 kPa. What is the pressure of the atmosphere gasses if the total pressure is 101.3 kPa? A container contains 10 g of oxygen gas, 80 g of nitrogen gas and 1 g of carbon dioxide. The total pressure of the container is 101.3 kPa, find: Mole fraction of each gas The partial pressure of each gas

Graham’s Law The velocity of particles is related to their temperature (ave. Kinetic Energy) and their mass. Simulation KE = ½ mv2 Therefore v = v is inversely proportional to the mass of the particle at any given temperature. For 2 gases (A and B)

Graham’s Law Applications At the SAME TEMPERAURE Molecules with smaller masses have greater velocities molecules with greater masses have smaller velocities DIFFUSION: The tendency of molecules to move toward areas of lower concentration. Molecules with greater velocities have greater rates of diffusion 2 effects on Diffusion rates: 1) Temperature: Higher temp = higher rate DIRECT 2) Mass: Smaller mass = higher rate INVERSE