1. GASES Kinetic molecular theory Gases and pressure The gas laws Ideal gas law

2. THE KINETIC-MOLECULAR THEORY OF MATTER

3. Kinetic-Molecular theory is based on the idea that particles of matter are always moving and this motion has consequences Solid particles Vibrate around A fixed point Liquid particles glide past one another Gas particles are in constant motion

4. GASES AND PRESSURE

5. PRESSURE IS THE FORCE PER UNIT AREA Since gas particles are in constant motion they collide with the with anything they come in contact with causing pressure. Ex) tires

6. ATMOSPHERIC PRESSURE The earth’s atmosphere exerts pressure on everything on earth, including you!!! Don’t think it effects you? ever have altitude sickness???

7. MEASURING PRESSURE A barometer is a device used to measure atmospheric pressure. A manometer is a device used to measure the pressure of a gas in a closed container

8. PRESSURE UNITS UnitSymbolCommon application KilopascalkPaScientific Millimeter of mercurymmHgBlood pressure Torr Vacuum pumps AtmosphereatmAtmospheric pressure

9. HOW THE PRESSURE UNITS ARE RELATED Make sure you know this because pressure can be given in any of these units and you may need to covert between the units ***1 atm = 760 mmHg *** 1 Torr = 1 mmHg *** 1atm = 101.3 kPa

10. TRY CONVERTING THESE PRESSURE UNITS (USE DIMENSIONAL ANALYSIS) 24.0 atm to kPa 1700 mmHg to atm 204 kPa to Torr

11. PRESSURE IS DEPENDENT ON: 1.Volume 2.Temperature 3.Number of molecules present

12. BASIC GAS LAWS Dalton’s law of partial pressures Boyle’s law Charles’ Law Gay-Lussac’s Law

13. 1.DALTON’S LAW OF PARTIAL PRESSURES States that the total pressure of a gas mixture is the sum of the partial pressures of each of its components P total = P 1 + P 2 + P 3 … Example: if 3 separate one liter container of oxygen each have 2.4 atm of pressure and are combined in a single one liter container what is the pressure inside the single container

14. Volume, Temperature, and Pressure are all related! So what happens when we hold each of those constant, one at a time?

15. 2. BOYLE’S LAW P 1 V 1 =P 2 V 2 States gas pressure and volume are indirectly (inversely) proportional at a constant temperature (if one goes up the other goes down)

16. CALCULATIONS WITH BOYLE’S LAW Use the formula P 1 V 1 =P 2 V 2 P1 = pressure 1 (initial) V1 = volume 1 (initial) P2 = pressure 2 (final) V2 = volume 2 (final) Pressure units must match Volume units must match

17. EXAMPLE A balloon filled with helium gas has a volume of 500. mL at a pressure of 1.00 atm. The balloon is released and reaches an altitude of 6.5 km where the pressure is 0.50 atm. If the temperature remains the same what is the new volume of the balloon?

18. 3. CHARLES’ LAW States that the gas volume and temperature are directly related at a constant pressure (one goes up the other goes up) Use the formula V1= initial volume V2= final volume T1=initial temperature T2= final temperature

19. TEMPERATURE UNITS IN GAS LAW PROBLEMS All gas law problems involving temperature must use Kelvin as the unit NOT CELCIUS!!! Convert: K = o C + 273 The Kelvin temperature scale is based on kinetic energy therefore at absolute zero there is no particle movement 0K = -273 o C = -459 F

20. CHARLES’ LAW EXAMPLE A sample of neon gas occupies a volume of 752 mL at 25 o C. What will the volume be at 50.0 o C if the pressure remains constant?

21. 4. GAY-LUSSAC’S LAW States that the pressure and temperature of a gas are directly related at a constant volume (if one goes up the other goes up) Use the formula: P 1 = initial pressure P 2 = final pressure T 1 = initial temperature T 2 = final temperature Pressure units must match; temperature must be in Kelvin

22. GAY-LUSSAC’S LAW EXAMPLE At 120.0 o C, the pressure of a sample of nitrogen is 1.08 atm. What will the pressure be at 205 o C, assuming constant volume?