Air: Chemistry in the Atmosphere

1. Air: Chemistry in the Atmosphere Mrs. Teates Newport High School

2. Lesson 1 – Properties of Gases • Essential questions: • How do temperature, volume, and amount of gas affect gas pressure? Vocabulary: compressibility, gas pressure

3. Exploring Properties of Gases • Atmospheric gases are usually colorless, odorless, and tasteless – but they are matter • Have definite chemical and physical properties • Complete the laboratory activity on gas properties.

4. Compressibility • Compressibility is a measure of how much the volume of matter decreases under pressure • Gases can expand to fill their container, unlike solids or liquids • The reverse is also true: • They are easily compressed, or squeezed into a smaller volume • This is the idea behind placing “air bags” in automobiles

5. In an accident, the air compresses more than the steering wheel or dash when you strike it. The impact forces the gas particles closer together because there is a lot of empty space between them. Crash Test Dummy

6. Variables that describe a gas • The four variables and their common units: 1. Pressure (P) in kilopascals 2. Volume (V) in Liters 3. Temperature (T) in Kelvin 4. Amount (n) in moles The amount of gas, volume, andtemperature are factors that affect gas pressure.

7. 1. Pressure - Common use? • Aerosol (spray) cans • gas moves from higher pressure to lower pressure • a propellant forces the product out • whipped cream, hair spray, paint • Fig. 14.5, page 416 • Is the can really ever “empty”?

8. 2. Volume of Gas • In a smaller container, the molecules have less room to move. • The particles hit the sides of the container more often. • As volume decreases, pressure increases. (think of a syringe)

9. 3. Temperature of Gas • Raising the temperature of a gas increases the pressure, if the volume is held constant. • The molecules hit the walls harder, and more frequently! • Fig. 14.7, page 417 • Should you throw an aerosol can into a fire? What could happen? • When should your automobile tire pressure be checked?

10. 4. Amount of Gas • When we inflate a balloon, we are adding gas molecules. • Increasing the number of gas particles increases the number of collisions • thus, the pressure increases • If temperature is constant- doubling the number of particles doubles the pressure

11. Pressure and the number of molecules are directly related • More molecules means more collisions. • Fewer molecules means fewer collisions. • Gases naturally move from areas of high pressure to low pressure because there is empty space to move into – a spray can is example. http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/gasesv6.swf

12. Lesson 2 – The Atmosphere • Essential Question: • How does the composition of the Earth’s atmosphere affect its properties and behavior? Vocabulary: atmosphere

13. Most of the atmosphere’s mass and all of its weather are within 10 to 15 km of the Earth’s surface. (troposphere) Ancient air trapped in glacial ice has about the same makeup as the current atmosphere. http://www.whfreeman.com/Chemcom/ For interactive atmospheric air. Structure of the Atmosphere

14. Graphing Atmospheric Data • In this exercise, you will graph the following: • Temperature vs. altitude • Pressure vs. altitude • Follow your handout for more details.

15. Lesson 3 – Gas Laws • Essential Questions: • How are the pressure, volume, and temperature of a gas related? Vocabulary: Boyle’s law, Charles’s law, Gay-Lussac’s law, combined gas law

16. Gas Laws • Boyle’s Law – pressure and volume • Charles’s Law – temperature and volume • Gay-Lussac’s Law – pressure and temperature • Combined Gas Law – pressure, temperature and volume • Ideal Gas Law

17. Boyle’s Law • Boyle was born into an aristocratic Irish family • Became interested in medicine and the new science of Galileo and studied chemistry.  • A founder and an influential fellow of the Royal Society of London • Wrote extensively on science, philosophy, and theology.

18. Boyle’s Law Gas pressure is inversely proportional to the volume, when temperature is held constant. • Pressure x Volume = a constant • Equation: P1V1 = P2V2 (T = constant)

19. - Page 419

20. Jacques Charles (1746-1823) • French Physicist • Part of a scientific balloon flight on Dec. 1, 1783 – was one of three passengers in the second balloon ascension that carried humans • This is how his interest in gases started • It was a hydrogen filled balloon – good thing they were careful!

21. Charles’s Law • The volume of a fixed mass of gas is directly proportional to the Kelvin temperature, when pressure is held constant. • This extrapolates to zero volume at a temperature of zero Kelvin.

22. - Page 421

23. Joseph Louis Gay-Lussac (1778 – 1850) • French chemist and physicist • Known for his studies on the physical properties of gases. • In 1804 he made balloon ascensions to study magnetic forces and to observe the composition and temperature of the air at different altitudes.

24. Gay Lussac’s Law • The pressure and Kelvin temperature of a gas are directly proportional, provided that the volume remains constant. • How does a pressure cooker affect the time needed to cook food?

25. Gay-Lussac’s Law Practice • Page 423 Sample Problem 14.3 • Practice Problems #11-12

26. The Combined Gas Law • The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas. • Contains all the other gas laws

27. Combined Gas Law Practice • Page 424 Sample Problem 14.4 • Practice Problems 13 & 14

28. Gas Law Webquest • Dangers of scuba diving video • http://player.discoveryeducation.com/index.cfm?guidAssetId=BF82E85A-8430-4435-AD26-E0AB071E3246&blnFromSearch=1&productcode=US • http://cmcweb.lr.k12.nj.us/webquest/brennan/scubachem.htm

29. Lesson 4 – Essential Questions • Under what conditions are real gases most likely to differ from ideal gases? Vocabulary: ideal gas law, ideal gas constant

30. Real Gases vs. Ideal Gases Real Gases Ideal Gases Particles have no volume. Particles have no attractive forces. Does not really exist, but allows us to do calculations with the gases. Real gases behave this way at a) high temperature, and b) low pressure. • Particles have volumes • Particles have attractive forces.

31. The Ideal Gas Law • Equation: P x V = n x R x T (PV=nRT) • Ideal Gas Constant = R = 8.31 (L x kPa) / (mol x K) • An ideal gas does not really exist, but it makes the math easier and is a close approximation. • Sample Problem 14.5 on page 427. • Complete practice problems #23 & 24 on page 427. • Practice worksheet.

32. Lesson 5 – Essential Questions • How does the release of greenhouse gases affect the way the carbon cycle regulates the amount of carbon dioxide in the atmosphere? Vocabulary: carbon cycle, greenhouse gases, limiting reactant

33. Climate • What is the climate? • What does global climate mean? • Earth's overall climate variability — such as average temperature, average precipitation, average intensity of winds, and other conditions of Earth's overall atmosphere and at its surface — separate from any specific weather events or local climate conditions. • Climate video - http://www.teachersdomain.org/resources/ess05/sci/ess/watcyc/climatechange/index.html

34. Carbon Cycle • The concentration of carbon in living matter is 18%, while it is 0.19% in nonliving matter. For life to continue, this carbon must be recycled. • Carbon in living matter vs. carbon in nonliving matter. • 71% of Earth’s carbon is found in the oceans.

35. Rising Levels of Carbon Dioxide • Without humans, CO2 levels would remain virtually unchanged. • Limestone CaCO3 is decomposed to CaO and CO2 is released. • Clearing forests takes away plants that would remove CO2 from the atmosphere. • Burning fossil fuels releases CO2 • Coal C + O2 → CO2 • Gasoline 2C8H18 + 25O2→16CO2 + 18H2O

36. Greenhouse Effect • CO2 in the atmosphere retards the radiation of heat from the earth back into space – “greenhouse effect” • If enough CO2 is added than can be removed by natural processes, then the temperature of the earth will increase. • Other greenhouse gases include nitrous oxide, chlorofluocarbons (CFCs), and methane.

37. Global Warming • Ten of the warmest years since 1880 have occurred since 1983. • Most climate specialists think earth’s temperature will increase 1.0° to 3.5°C in the next 100 years. http://www.teachersdomain.org/resources/phy03/sci/ess/watcyc/co2/index.html

38. Projected Effects of Global Warming • Oceans will rise 5cm each decade over the next century due to melting of ice caps and expansion of ocean water with increased temperature. • Flooding in major cities due to increased ocean levels. • Warmer temperature results in increases in extreme weather events. • Warmer atmosphere can hold more moisture, making big storms more likely. • Shorter winters with more blizzards • http://channel.nationalgeographic.com/channel/sixdegrees/book.html • (Open your laptop up and view this page.)

39. Global Warming Videos & Discussion • Video on Global Warming • http://www.teachersdomain.org/resources/phy03/sci/phys/matter/greenhouse2/index.html • Video titled “Global Warming: Carbon Dioxide and the Greenhouse Effect” • http://www.teachersdomain.org/resources/phy03/sci/ess/watcyc/co2/index.html

40. Kyoto Protocol • Sets ambitious goals for reducing greenhouse gas emissions. • For industrialized nations, involves developing energy efficient technologies, relying more heavily on renewable energy, and using alternative processes that don’t produce carbon dioxide. • Example – use of biofuels possibly reduces carbon emissions. Dark green = countries that have signed and ratified the treaty Yellow = signed by not yet ratified Grey = not decided yet Red = no intention of ratifying SnapShot of Energy Use Video - http://www.teachersdomain.org/resources/tdc02/sci/life/eco/energyuse/index.html

41. Lesson 6 – Essential Questions • What are the major sources of air pollution and how do they affect the environment? • Using the properties of gases, how can air pollution be controlled? Vocabulary: air pollutants, particulates, synthetic substances, VOCs, smog, synergistic interactions, photochemical smog, electrostatic precipitation, mechanical filtering, scrubbing

42. Air Pollution • Sources of air pollution are both natural and manmade. • Natural - volcanoes • Manmade – exhaust pipes, smokestacks, burning of fossil fuels • Several categories of air contaminants • Primary air pollutants – directly enter the atmosphere • Methane gas – produced by natural gas production and naturally through anaerobic bacteria • Secondary air pollutants – formed in the atmosphere by chemical reactions between primary air pollutants and natural components of air • Sulfur trioxide is produced from oxygen gas and sulfur dioxide • Particulates – all solid particles that enter the air • Natural – forest fires, wind erosion, volcanic eruptions • Manmade – vehicle emissions, power plants • Synthetic substances – present solely from human activities • chlorofluorocarbons

43. Carbon dioxide Nitrogen oxides Carbon monoxide Sulfur dioxide Particulate Matter Lead Ozone Major Air Contaminants

44. Change is Occuring

45. Smog in the Environment • Smog is a combination of smoke and fog • Caused by the interaction of air contaminants with meteorological conditions. • Smog can cause severe respiratory distress and even has been listed as the cause for 4000 deaths in London in 1952. • Photochemical smog is the smog found over cities that is due to the reaction of chemicals in the air with light. • Major causes of this are nitrogen oxides, ozone, and hydrocarbons.

46. Pollution Control and Prevention • New energy technologies • Solar power, wind power, nuclear power • Energy conservation measures • More efficient combustion engines • Removal of pollution from factory emissions • Electrostatic precipitation – charged particles are used • Mechanical filtering – similar to a large vacuum cleaner • Scrubbing – uses chemical reactions to control particles and sulfur oxides

48. Controlling Automobile Emissions • Why would it be more difficult to control automobile emissions than air pollution from U.S. power plants and industries? • Clean Air Act of 1970 • Invention of the catalytic converter • Clean Air Act of 1990

49. Ozone and CFC’s: A Success Story • Ozone layer of earth protects us from the solar radiation that would cause genetic damage • CFC’s have depleted the ozone layer • Were found in refrigerants, aerosols, cooling fluids in air conditions, cleaning solvents • Montreal Protocol terminated the US production of CFC’s in 1975.

50. What will you do? • Pollution is a global and local issue. • What will you do to slow the rate of global warming? • What suggestions do you have to reduce pollution?