1. Kinetic Molecular Theory and Gas Laws Day 1

2. Kinetic-Molecular Theory – explains how particles in matter behave 1. All matter is composed of small particles that are far apart. Gas is mostly empty space. 2. Particles are in constant, random motion. 3. Particles collide with each other and walls of their containers: collisions create pressure 4. Collisions are elastic = no KE lost 5. No attractive/repulsive forces between particles. Molecules move in straight lines.

3. PHASESOLIDLIQUIDGAS Kinetic EnergyLowMediumHigh ShapeRigidFluidFluid – fills container; diffusion ForcesStrongMediumWeak VolumeDefinite Indefinite CompressibilityIncompressible COMPRESSIBLE! “squish!” DensityHigh (particles close together) MediumLow (spread out)

4. Defining a Gas Gases include 4 variables: 1.Volume Measured in milliliters (mL) or Liters (L) 1000 mL = 1 L

5. 2. Temperature  Average kinetic energy of particles (how fast they go)  Measured in Kelvin  K = o C + 273  Ex: Convert 17 o C to Kelvin:  17 o C + 273 = 290 K

6. 3. Pressure Force exerted by a gas per unit area on a surface. Example: Pounds/in 2 or psi Results from the simultaneous collisions of billions of gas particles with the walls of the vessel containing the gas. 760 mm Hg = 1 atmosphere = 101.3 kPa (torr)

7. Measuring Atmospheric Pressure Measured with a barometer. A barometer uses a column of mercury that rises to an average height of 760 mmHg at sea level. 1 atmosphere (1 atm)

8. Standard Temperature and Pressure (STP) The conditions of standard temperature and pressure are = 1.0 atm pressure and = 273 K (or 0  C). @STP 1 mole of gas = 22.4 L of gas

9. Example 1 The atmospheric pressure in Denver, CO is 0.830 atm on average. Express this pressure in mm Hg.

10. 0.83 atm  mm Hg 1 atm = 760 mm Hg 0.83atm 1 atm 760 mm Hg = 630.8 mm Hg

11. Example 2 Convert a pressure of 175 kPa to atmospheres.

12. 175 kPa  atm 101.3 kPa = 1 atm 175 kPa 101.3 kPa 1 atm 1.72 atm

13. 4. Moles! We already have heard that 1 mol = 22.4 L We can add or take away moles which may affect the other variables (more on this to come!)

14. Gas Law Foldable Fold the left and right to the middle. Cut along solid lines (but only to the crack!)

15. Dalton’s Law of Partial Pressure The pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases. P Total = P 1 + P 2 + P 3 ….

16. Example A balloon is filled with air (O 2, CO 2, & N 2 ) at a pressure of 1.3 atm. If P O 2 = 0.4 atm and P CO 2 = 0.3 atm, what is the partial pressure of the nitrogen gas?

17. P Total = P 1 + P 2 + P 3 …. P total = P O 2 + P CO 2 + P N 2 1.3 atm = 0.4 atm + 0.3 atm + P N 2 P N 2 = 0.6 atm