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Unit A Thermochemical Changes The Plan • Section 11.1-Energy demands & sources. https://sites.google.com/a/freeholdtwp.k12.nj.us/jaclynkelly/science/ener gy-slam-poem http://energypost.me/ Energy • Energy is the capacity to do work. • The direction of energy flow can be expressed as either: exothermic (out) or endothermic (in). • 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 Photosynthesis • Major natural contributor to stored chemical energy on Earth. • Takes energy from the Sun (radiant – electromagnetic energy) & converts it into chemical energy. 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) 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, liquid water, & energy. •It is an exothermic reaction. The equation below represents the process of cellular respiration C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) + energy 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. 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 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: 1. Heating (15%) 2. Transportation (30%) 3. Industry (40%) 4. Commercial & institutional (15%) 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-steptoward-better-solar-energy-systems.html Alternative Lifestyle • • • • • Improved insulation and design Walking, biking, mass transit Alcohol/gasohol & hydrogen fuels Improved efficiency & waste heat recovery Water & heat conservation 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: "EXOTHERMIC" Heat Light Furnace Firefly Energy from Chemical Changes Battery Electricity Car Engine Mechanical Energy "ENDOTHERMIC" Heat Light Cooking Photosynthesis Energy Stored in Chemicals Electrolysis NH3(g) Production Electricity Mechanical Energy 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 Society's major source of energy is from chemical reactions. Examples include: 1. burning coal (carbon) and oil (hydrocarbons) to generate steam to turn electrical generators. 2. burning gasoline/diesel (hydrocarbons) to propel vehicles. 3. burning natural gas or heating oil (hydrocarbons) to heat buildings and water. 4. electrochemical reactions in batteries. 5. producing, refining and shaping metals and plastics (industry). 6. food consumption (humans, animals). 7. fertilizer production. When is it predicted that fossil fuels in Alberta will be depleted? 2020! In the News Efforts aimed at making it easier to invest in green energy improvements that in the past have been impractical or unaffordable. New Research Integrating solar technologies into coal-fired power plants could ease the transition from fossil fuels to renewable energy sources. Read p. 478 - 482 Section 11.1 Questions #1-8 (omit 2 & 6), 11a & 12. Enzymes Read pgs. 535 – 541 pg. 542 Section 12.3 Questions #’s 1 – 6