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The Behavior of Gases, Chapter 14 (Unit 1) Mr. Samaniego Lawndale High School California Standards Gases and Their Properties 4. The kinetic molecular theory describes the motion of atoms and molecules and explains the properties of gases. As a basis for understanding this concept: a. Students know the random motion of molecules and their collisions with a surface create the observable pressure on that surface. c. Students know how to apply the gas laws to relations between the pressure, temperature, and volume of any amount of an ideal gas or any mixture of ideal gases. Thinking Map Draw a Circle Map on Gases. Gases Phases of Matter Direct and Inverse Relationships As more people watch football, less watch tv shows. Inverse More people listen to an artist as they become more popular. Direct The more money you make, the more money you spend. Direct Inverse vs. Direct Which relationship is direct or inverse? Volume vs. Temperature 3.0 Volume (L) 3.0 Direct 2.0 1.0 0.0 Direct 2.0 1.0 0.0 0 200 400 600 Temperature (K) 800 1000 0 200 Pressure vs. Volume Pressure (kPa) Pressure (atm) Pressure vs. Temperature 300 250 200 150 100 50 0 Inverse 0.0 0.5 1.0 1.5 2.0 Volume (L) 2.5 3.0 400 600 Temperature (K) 800 1000 The Gas Laws Boyle’s Law Charles’Law P1V1 P2V 2 V1 T 1 Gay-Lussac’s Law Combined Gas Law Ideal Gas Law V2 T2 P1 T 1 P2 T2 P1V1 T 1 P2V 2 T2 PV nRT Temperature There are three common units temperature is measured in: Celsius ___________ (oC), Fahrenheit (oF), and _________ Kelvin (K) Temperature The important temperature unit in describing Gas behavior is Kelvin ___________ (K). Conversion: 273 Kelvin = Celsius + _____ Pressure There are five common units pressure is measured in: kilopascals ____________ (kPa), ______________ (atm), mm of atmospheres mercury (mm Hg), Torr (Torr), and pounds/inch2 (lbs/in2) Conversion Factors 101.325 kPa = 760 760 Torr = _______ 14.7 lbs/in2 1 atm = _______ ___ mm Hg = ____ Amount There are some common unit amounts is measured in : moles ________(mol), particles, atoms, etc. The variable n is used for # of moles The conversion is: 6.02x1023 1 mol = ____________ (anything) Volume There are three common units volume is measure in: liters milliliters _________ (L), _____________ (mL), cubic centimeters ______ _____________(cm3) Conversion Factors 1,000 mL= _______ 1,000 cm3 1 L= ______ Gas Constant, R There are different ways of expressing constant R in solving gas the gas _________ problems. It only depends on the units _______ being used. As long as the units match, the right value is being used. R = 8.31 L*kPa/(mol*K) = 0.0821 L*atm/(mol*K) LOGIC with Volume/Pressure increases then the • If temperature __________, volume will _________. increase increases then the pressure • If volume __________, decrease will __________. LOGIC with Pressure increases • If temperature __________, then the increase pressure will _________. STP: Standard Temperature and Pressure, T = 0 oC P = 1 atm = 101.325 kPa = 760 Torr Strategies in Problem Solving: Gas Problems Strategies in Problem Solving: Gas Problems Identify known/ uknown values must include proper units!!! Conversions use LOGIC (You can do it!) must have unit agreement Calculator multiply across top divide across bottom Poster Design • • • • Choose 1 Gas Law Name it and show the formula Include 1 drawing Describe what happens: “If temperature increases…” • 5 points Warm-up (2-8-12/2-9-12) Copy problems and answers into notebook: 1. What do the following items measure? a) P pressure b) V volume c) n Amount (in moles) d) R Gas constant e) T temperature 2. Which temperature unit must be used in Gas Law calculations? Kelvin 3. How do you convert degrees Celsius to Kelvin? Add 273 (to Celsius) Benchmark Reflection Warm-up (2-9-12/2-10-12) Copy problems and answers into notebook: 1. What happens to the volume if the pressure increases? It decreases 2. What happens to the pressure if the temperature decreases? It decreases 3. What happens to the temperature if the volume decreases? It decreases Describe #’s 1-3 as “Direct” or “Inverse” relationships. 1. inverse 2. direct 3. direct 5. List the units that apply to each of the following: a) Pressure b) volume c) temperature 4. atmospheres, kPa liters Kelvin Warm-up (2-13-12/2-14-12) Copy problems and answers into notebook: 1. What is the standard temperature (see p. 300)? I. 0 K a) I only II. 0 oC b) II only III. 273 K c) III only d) II and III 2. Which Centigrade (Celsius) temperature is the same as 298 K? a) 250C b) 2120C c) 5210C d) 5960C 3. The pressure exerted by a gas is due to a) the chemical nature of the container; b) the color of the gas; c) the height of the container above sea level; d) the diameter of the gas molecules; e) the collisions of the gas molecules with the walls of the container. e) 10580C Pressure • What is pressure created by? The random collision of molecules and their collisions with a surface. (Standard 4a) Boyle’s Law 1. A gas has a volume of 12.5 L at 450. kPa pressure. What pressure is needed to change the volume of the gas to 6.25 L? Boyle’s Law 2. A gas has a volume of 284 mL while at 101.325 kPa. What new volume will it have if the new pressure is 25.3 kPa? Boyle’s Law 3. An unknown pressure is maintained while a gas has a volume of 468 mL. If it expands to 702 mL while the gas has a new pressure of 1.80 atm, what was the original pressure? Boyle’s Law 4. A gas at 203 kPa pressure and unknown volume changes to 24.5 L while under the new pressure of 305 kPa. What was the original volume? Boyle’s Law 4b. A gas at 502 kPa pressure and unknown volume changes to 355 L while under the new pressure of 1,500 kPa. What was the original volume? Charles's Law 5. A gas has a volume of 91 mL at a temperature of 910C. This gas is kept at constant pressure but its temperature is reduced to 00C. What should the new volume be? (remember to use Kelvin) Charles's Law 6. Calculate the original temperature that 350. mL of oxygen has, if it occupies 525 mL, while the temperature is 301 K. Charles's Law 7. Gas in a tire takes up 12.5 L of space at 22.0oC. What new temperature in Kelvin should it have if the new volume is 37.5 L? Gay-Lussac’s Law 8. The air in a car has a pressure of 1.00 atm while the car is at 20.0oC. If the air pressure does not escape from the car, what new pressure would it have if it heated to 352oC? Gay-Lussac’s Law 9. The air in a sealed container has a pressure of 1.00 atm while at 32.0oC. What new temperature would it have if the pressure went up to 3.00 atm? Combined Gas Law 10. An air bubble occupies a space of 1.52 mL while at a depth in the ocean where there is 2.50 atm of pressure and a temperature of 15.3 oC. Find the volume of the bubble just before it reaches the surface, with a pressure of 1.00 atm and a temperature of 25.0 oC. Boyle’s Law 11. A scuba diver at 20.0 m experiences a pressure of 2.50 atm. The diver inflates her lungs to 1.8 L and holds her breath as she heads to the surface her lungs are at a constant temperature. What would the volume of her lungs expand to as she breaks the surface where the pressure is 1.00 atm? Combined Gas Law 12. A balloon is inflated to 1.00 L at 1.00 atm, 27°C. The balloon rises to an altitude of 10,000 meters where the temperature is 1590 K and the pressure is 0.500 atm. What is the new volume of the balloon? Combined Gas Law 13. A balloon is inflated to 3.25 L at 1.00 atm, with an unknown temperature. The balloon rises to an altitude of 10,000 meters where the temperature is 1,380 K and the pressure is 0.409 atm and a volume of 13.5 L. What is the original temperature of the balloon? Clearing Fractions Dalton’s Law Dalton’s Law of Partial Pressures: at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases. Ptotal = P1 + P2 + P3 + … Practice Determine the total pressure exerted by the following gases: 23.4 kPa of oxygen, 14.8 kPa of nitrogen, and 28.3 kPa of carbon dioxide. Follow-up Assignment • Chapter 14, Behavior of Gases p. 439: 39-54, and 59 [Don’t write questions, just answers.]