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Energy Sources and Chemical Reactions: Understanding the Flow of Energy

Explore the interplay between energy sources and chemical reactions, from photosynthesis to hydrocarbon combustion. Learn about the demands for energy and alternative sources like solar and nuclear power. Understand exothermic and endothermic reactions and their significance in our daily lives. Discover how societal energy needs are met through various chemical processes.

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Energy Sources and Chemical Reactions: Understanding the Flow of Energy

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  1. Unit A Thermochemical Changes

  2. The Plan • Section 11.1-Energy demands & sources. https://sites.google.com/a/freeholdtwp.k12.nj.us/jaclynkelly/science/energy-slam-poem http://energypost.me/

  3. Energy • Energy is the capacity to do work. • The direction of energy flow can be expressed as either: exothermic (out) or endothermic (in).

  4. Energy will flow from "hot" to "cold" until "thermal" equilibrium is attained, that is, the substance and environment are at the same temperature! http://www.physicsclassroom.com/class/thermalP/Lesson-1/What-is-Heat

  5. Photosynthesis • Major natural contributor to stored chemical energy on Earth. • Takes energy from the Sun (radiant – electromagnetic energy) & converts it into chemical energy.

  6. Photosynthesis • Carbon dioxide and water react in plants in the presence of sunlight to produce glucose & oxygen. • It is an endothermic reaction. • The equation below represents the simplified process of photosynthesis. 6 CO2(g) + 6 H2O(l) + energy → C6H12O6(aq) + 6 O2(g)

  7. Cellular Respiration • The chemical energy stored in the process of photosynthesis is accessed during the process of cellular respiration. • In this process, glucose and oxygen react to produce carbon dioxide, liquidwater, & energy. • It is an exothermic reaction. The equation below represents the process of cellular respiration C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) + energy

  8. Hydrocarbon Combustion • Hydrocarbon combustion is an exothermic reaction just like cellular respiration. • E.g., Propane: C3H8(g) + 5O2(g) →3CO2(g) + 4H2O(g) + energy • Notice that in hydrocarbon combustion, water vapor is formed, whereas in cellular respiration, liquid water is formed. Other than that, the equations are almost identical.

  9. Fossil Fuels • Biogenic hypothesis: Fossil fuels (e.g., coal & natural gas) had their origins in deposits of plants & animal matter, which got their energy from the sun. • Supports the claim that fossil-fuel energy has its origins in the solar energy from our sun. http://www.toonpool.com/cartoons/first%20fossil%20fuel_6415

  10. Fossil Fuels • Fossil fuels are a major store of chemical energy that we use in everyday lives. • In Alberta, ~20% of jobs are in the energy sector. • There are four major demands for energy from fossil fuels: • Heating (15%) • Transportation (30%) • Industry (40%) • Commercial & institutional (15%)

  11. Some Alternative Energy Sources • solar heating • geothermal energy • biomass gas • hydroelectricity • nuclear power http://www.mtu.edu/news/stories/2012/july/more-heat-more-light-step-toward-better-solar-energy-systems.html

  12. Alternative Lifestyle • Improved insulation and design • Walking, biking, mass transit • Alcohol/gasohol & hydrogen fuels • Improved efficiency & waste heat recovery • Water & heat conservation

  13. Chemical Change • The reactant(s) have different chemical composition than the product(s). E.g., H2O(l) O2(g) + H2(g) • Some possible energy conversions:

  14. "EXOTHERMIC" Heat Light Furnace Firefly Energy from Chemical Changes Battery Car Engine Electricity Mechanical Energy

  15. "ENDOTHERMIC" Heat Light Cooking Photosynthesis Energy Stored in Chemicals NH3(g) Production Electrolysis Electricity Mechanical Energy

  16. Chemical Change • In chemical reactions, the products have different chemical compositions than do the reactants. Also, the total potential energy of all the products is different than the total potential energy of the reactants. • This is why energy is always either absorbed or released in any chemical reaction. • Exothermic reactions release energy & endothermic reactions absorb energy

  17. Society's major source of energy is from chemical reactions. Examples include: • burning coal (carbon) and oil (hydrocarbons) to generate steam to turn electrical generators. • burning gasoline/diesel (hydrocarbons) to propel vehicles. • burning natural gas or heating oil (hydrocarbons) to heat buildings and water. • electrochemical reactions in batteries. • producing, refining and shaping metals and plastics (industry). • food consumption(humans, animals). • fertilizer production.

  18. When is it predicted that fossil fuels in Alberta will be depleted? 2020!

  19. In the News Efforts aimed at making it easier to invest in green energy improvements that in the past have been impractical or unaffordable.

  20. New Research Integrating solar technologies into coal-fired power plants could ease the transition from fossil fuels to renewable energy sources.

  21. Homework: • Read p. 478 - 482 • Section 11.1 Questions • #1-8(omit 2 & 6), 11a & 12.

  22. Enzymes

  23. Homework: • Read pgs. 535 – 541 • pg. 542 Section 12.3 Questions #’s 1 – 6

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