ENERGY Reading: Supplemental Text Materials Chapter 11: pages 225-238
Energy Ability to do work Unit: Joule (J) J = (kg x m 2 )/s 2
Power Energy over time Watts (W) 1 W = 1J/s
Power is energy over time http://www.dodgeglobe.com/images/102901/hiker.jpg
Types of Energy Mechanical Electrical Chemical Radiant (Light) Heat Nuclear
Mechanical Energy Potential Energy Kinetic Energy
Stored energy Potential Energy
Kinetic Energy Energy of motion
Energy Conversion From high-grade to lower-grade forms
Energy conversion Mechanical to Electrical
Energy conversion Chemical to mechanical
Energy conversion Radiant to heat Radiant to electrical
Steam Turbine http://www.uaf.edu/energyin/webpage/pages/heat_engines/steam_and_gas_turbines.htm
Earth s Energy Sun 99+% of Earth s energy Internal heat radioactive decay gravitational pressure
Sun s Energy Radiant energy Released by fusion Hydrogen fused into Helium 1.73 x 10 17 watts received by Earth from Sun Converted by plants into chemical energy
Photosynthesis 6 CO 2 + 6 H 2 O sun energy C 6 H 12 O 6 + O 2 Converts CO 2 and H 2 O to sugar and O 2 Created the level of oxygen present in today s atmosphere Ancient algae in Archean and Proterozoic oceans released O 2 by photosynthesis
Source of energy not from Sun Rare deep sea vent communities Sulfurous hotsprings supports bacteria Other organisms subsist on bacteria Larger creatures can survive on the bacteria-eating organisms
http://www.punaridge.org/doc/factoids/biology/ Black Smoker
http://www.punaridge.org/doc/factoids/biology/ Vent community
Tube worm and crab http://www.punaridge.org/doc/factoids/biology/
Energy and Chemical Reactions Temperature affects rate of reactions More molecule collisions More energy to break chemical bonds Concentration of reactants Presence of catalyst Peroxide 2 H 2 O 2 2 H 2 O + O 2 proceeds slowly Add platinum: takes seconds, not years
Energy and Chemical Reactions Heat released or consumed in chemical reactions Measured in calories Food calorie is a kilocalorie (kcal) 1 Joule = 0.24 calories Energy shown in equation C 3 H 8 + 5 O 2 3 CO 2 + 4 H 2 O + 526 kcal
Reaction energy EXOTHERMIC heats up environment ENDOTHERMIC absorbs heat from environment
Exothermic Reaction C 3 H 8 + 5 O 2 3 CO 2 + 4 H 2 O + 526 kcal Burn 2 moles of propane 2 x 526 kcal = 1052 kcal Burn 308 g of propane 308 g (1 mole/44g) = 7 moles 7 moles x 526 kcal = 3682 kcal
Endothermic reaction N 2 + O 2 + 4.32 kcal 2 NO 5 moles of nitrogen, reacting with 5 moles of oxygen Consumes 5 x 4.32 kcal = 21.6 kcal
Conservation of Energy Energy is not created or destroyed First Law of Thermodynamics
Heat Flow From objects with heat to those with less Change form from high quality to lower quality Chemical to heat friction
Entropy Lack of order of systems Nature tends toward disorder greater entropy Takes energy to overcome entropy Oil spill on Columbia River CFC released into atmosphere
Energy sources Wood chemical energy stored by plants Kinetic energy Water power to grind grain Wind to pump water Fossil fuels
Fossil fuels Burn readily Reaction is oxidation Release heat energy
Fossil fuels Coal Petroleum Natural Gas
First law of thermodynamics Conservation of energy Cannot create or destroy energy (But we can convert to less-useful form)
Fossil fuels Non renewable From ancient organisms Extracted from Earth
Coal C + O 2 CO 2 Anthracite Bitumen Lignite
Coal Incompletely decayed plants Burial pressure releases O 2 and H 2 Carbon remains Paleozoic Pennsylvanian coal, Carboniferous Era
Carboniferous Period Forest http://palaeos.com/paleozoic/carboniferous/carboniferous.htm
Coal formation 1
Coal formation 2
Coal formation 3
Coal formation 4
Coal formation Summary
Coal Must be mined Pollutants in coal Sulfur leads to acid rain Also contains mercury, arsenic, nitrates
Coal Coke is made by heating coal Byproduct refined into organic chemicals
Natural Gas Mostly methane CH 4 + 2 O 2 CO 2 + 2 H 2 O + heat Excellent, clean-burning fuel Raw material for plastics and other chemicals
Petroleum Replaced coal by about 1950 Complex hydrocarbon molecules Derived from fats Combustion products are carbon dioxide and water
Petroleum C 8 H 18 + 18 O 2 16 CO 2 + 18 H 2 O Also contains some sulfur compounds Fuel oil is fairly clean Burning gasoline results in smog Internal combustion engines inefficient