Slide 1

Gases & Atmospheric Chemistry Slide 2 Read 11.1 (p. 516 519) Draw 3 particle pictures of the different states of matter. Include a container in your diagram. Add symbols to illustrate the motion of the particles. Volunteers? V gas =V container Define: KE, T Explain pop can demo. Define: P Slide 3 Introduction Demo 1: Water and Cue Card Why does the water stay in the glass? Demo 2: Pop Can What is happening in terms of STATES of water? Liquid Gas Liquid What is happening in terms of VOLUME of water? Small EXTREMELY LARGE Small 1 mol H 2 O (l) = 18 mL or 0.018L 1 mol of H 2 O (g) = 22.4 L Slide 4 We are surrounded by gases! Air (or the Atmosphere) is made up of: This air is colliding with usthis is called PRESSURE Or specifically the pressure we feel is Atmospheric Pressure What would the pressure be like on top of Mount Everest? Pressure: force exerted on an object per unit of surface area Air pressure= 1 atmosphere= 1 atm Slide 5 States of Matter How do intermolecular forces of attraction differ between states? Generally, how is particle size related to states of matter? CH 4 vs. C 5 H 12 Larger molecules= higher boiling points= liquid @ room temp Why???? The bigger the molecule the more opportunities for temporary dipoles to formdispersion forces add up and this increase the IMF of attraction Are all states compressible? Only gaseswhat is condensation? Slide 6 Types of Kinetic Energy Every moving particle has energy= kinetic energy Kinetic=motion Solid= vibrational motion Liquid= rotational and vibrational motion Gas= Translational, rotational, and vibrational motion Slide 7 Kinetic Molecular Theory of Gases The volume of an individual gas molecule is negligible compared to the volume of the container.* No attractive or repulsive forces between gas molecules.* Gas molecules move randomly in all directions, in straight lines (translational, rotational, vibrational). Perfect elastic collisions between gas molecules (i.e. no loss of kinetic energy). An increase in temperature will increase the motion of molecules. This means there is an increase in the average kinetic energy. * Assumptions for an IDEAL GAS Slide 8 What can affect kinetic energy? TEMPERATURE! How? Temperature= Kinetic energy How is pressure affected? Temperature= Kinetic energy = Pressure How is volume affected? Temperature= Kinetic energy = Pressure= Volume of Gas* *space that the gas take up BUT usually V gas = Volume container * Temperature is a measure of the average kinetic energy Slide 9 Pressure The force exerted on an object per unit of surface area P= F = N = Pa A m 2 Pressure: kinetic motion and collisions with surroundings Atmospheric Pressure is what we feel around us. - Air molecules have a mass. -They are pulled by gravity (acceleration of objects on earth= 9.81 m/s 2 or 32.2 ft/s 2 ) to exert pressure on Earth. Slide 10 Units of Pressure Pressure can be measured by: Atmospheres= 1 atm KiloPascals (SI Unit)= 101.3 kPa Millimeters of Mercury= 760 mmHg (1 st mercury barometer) Torricellis= 760 torr Pounds per square inch (Imperial)= 14.7 psi 1 atm= 101.3kPa= 760 mmHg= 760 torr= 14.7 psi How many kPa are in 3.57 atm of pressure? Slide 11 Discovering Pressure Barometer= 1 st instrument to measure air pressure Torricellis Barometer Torricelli found that air pressure at 0 C 1 atm= 101.3kPa= 760 mmHg= 760 torr= 14.7 psi Standard Temperature and Pressure (STP) 0C 101.3kPa Standard Ambient Temperature and Pressure (SATP) 25C 100kPa 760mm ~ 30 inch Slide 12 Kelvin Scale Charles found that the x- intercept would always be - 273C Kelvin (c.1800) inferred that at -273C VOLUME WOULD BE ZERO (molecular motion would cease, NO kinetic energy) p. 549 #1,2 0 K= -273C= Absolute zero T K = C + 273.15 K: No negative values! Slide 13 Charles Law Gay-Lussac (c.1800) referenced Charles work, and it became known as Charles Law: the volume of a fixed mass of gas is proportional to its temperature (K) when the pressure is kept constant V 1 = V 2 T 1 T 2 T MUST be K! Practice Pg. 552 #2 Slide 14 Boyles Law Mathematically: P 1 V 1 = P 2 V 2 p. 559 #1,2 Boyles Law (1662): the volume of a given amount of gas at constant temperature, varies INVERSELY with the applied pressure If we change the pressure by a factor of x, then the volume will change inversely by that same factor Slide 15 Gay-Lussacs Law Recall: 1. Temperature is a measure of average kinetic energy 2. V gas = Volume of container Gay- Lussacs Law: the pressure of a fixed amount of gas, at constant volume, is directly proportional to its Kelvin temperature. P 1 = P 2 T 1 T 2 p. 559 #3 MUST use K! Practice Pg. 559 Q: 1-3 Slide 16 Combined Gas Law Recall: STP 0C/273K & 101.3kPa SATP 25C/298K & 100kPa Combine: 1. Bolyes Law P i V i = P f V f 2. Charles Law V i = V f T i T f 3. Gay-Lussacs Law P i = P f T i T f Ex. A sample of gas has a volume of 150mL at 260K and 92.3kPa. What will the new volume be at 376k and 123 kPa? P 1 V 1 = P 2 V 2 p. 560 #1-3 T 1 T 2 T MUST be K! Slide 17 Daltons Law of Partial Pressures Imagine mixing 3 different gases each having a different pressure What would the final pressure be? Daltons Law of Partial Pressures: the total pressure of a mixture of gases is the sum of the pressures of each of the individual gases Ex. What is the pressure of O 2 in the atmosphere? P total = P 1 + P 2 + P 3 + +P n Practice Pg. 594 #1-4 Pg. 596 #1-3