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Gases & Atmospheric Chemistry

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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

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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

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We are surrounded by gases! Air (or the Atmosphere) is made up of: This air is colliding with us…this 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

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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= room temp Why???? The bigger the molecule the more opportunities for temporary dipoles to form…dispersion forces add up and this increase the IMF of attraction Are all states compressible? Only gases…what is condensation?

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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

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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

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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

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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.

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Units of Pressure Pressure can be measured by: Atmospheres= 1 atm KiloPascals (SI Unit)= kPa Millimeters of Mercury= 760 mmHg (1 st mercury barometer) Torricelli’s= 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?

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Discovering Pressure Barometer= 1 st instrument to measure air pressure Torricelli’s 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) 0°C 101.3kPa Standard Ambient Temperature and Pressure (SATP) 25°C 100kPa 760mm ~ 30 inch

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Kelvin Scale Charles found that the x- intercept would always be - 273°C Kelvin (c.1800) inferred that at -273°C VOLUME WOULD BE ZERO (molecular motion would cease, NO kinetic energy) p. 549 #1,2 0 K= -273°C= “Absolute zero” T K = °C K: No negative values!

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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

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Boyle’s Law Mathematically: P 1 V 1 = P 2 V 2 p. 559 #1,2 Boyle’s 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

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Gay-Lussac’s Law Recall: 1. Temperature is a measure of average kinetic energy 2. V gas = Volume of container Gay- Lussac’s 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

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Combined Gas Law Recall: STP 0°C/273K & 101.3kPa SATP 25°C/298K & 100kPa Combine: 1. Bolye’s Law P i V i = P f V f 2. Charles Law V i = V f T i T f 3. Gay-Lussac’s 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!

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Dalton’s Law of Partial Pressures Imagine mixing 3 different gases each having a different pressure… What would the final pressure be? Dalton’s 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

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