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APES CHAPTER 2 Energy The ability to accomplish WORK and: Move or change position Physical composition Absorb energy & use it to organize and reorganize molecules Change temperature ○ Example: photosynthesis, cellular respiration Ultimate source of energy on Earth: ○ The sun ○ Radioactive decay in core (Geothermal) Energy: Forms, Quality, Changes and Laws Energy - The capacity to do work or transfer heat Radiation - form of energy, ultimate source is the sun (or other stars) Transfer of Energy Radiation – transfer of energy by waves or rays Conduction – the transfer of heat between two parts of a stationary system at different temperatures. Usually solids. Convection – transfer of heat by movement in liquids or gases. Density differences account for motion. How the Sun Heats the Earth Radiation Conduction Convection Evaporation absorbs energy Condensation releases energy Know these!!!!! Energy: Forms, Quality, Changes and Laws Kinetic Energy (of motion) ○ Energy contained in moving objects. ○ Ex: Wind, flowing water, electricity, heat Potential Energy (of position) ○ Stored, latent energy available for use. ○ EX: Water behind a dam, chemical energy stored in bonds Measurements of Energy ○ Joule (J), kilowatt-hour (kWh), calorie (c), Calorie (C), British thermal unit (Btu) 8 Energy: Forms, Quality, Changes and Laws Thermodynamics First Law – Conservation of Energy ○ Energy is neither created nor destroyed, but can be transferred or transformed. All energy sources are finite (limited). Second Law – Change in Quality ○ Change from more-ordered to less-ordered ○ The quantity of energy remains the same, but the ability to do work diminishes (quality) ○ With each energy transfer or transformation, some energy is lost as waste. ○ Heat is usually the “waste” No process is 100% efficient. 11 Second Law of Thermodynamics Solar energy Chemical energy (photosynthesis) Waste heat Mechanical energy (moving, thinking, living) Chemical energy (food) Waste heat Waste heat Waste heat Rule of 10 Fig. 2-11, p. 32 Second Law in Nature Energy flows through food chains and is never recycled. Must be continually renewed by consumption. Energy must be constantly supplied to an ecosystem . . . . By? ENERGY TRANSFER BETWEEN TROPHIC LEVEL IS ONLY 10% EFFICIENT Energy Efficiency & Quality Energy Efficiency - The ratio of the amount of work that is done to the total amount of energy that is introduced to the system. Ex: Difference between woodstoves and fireplaces Energy Quality – the ease of which an energy source can be used for work. Ex: Gasoline vs. wood Energy: Forms, Quality, Changes and Laws High quality energy Concentrated and can do useful work Oil in Saudi Arabia, Gasoline, food Low quality energy Dispersed and does little useful work Oil in Ocean, wood A fireplace that is 10% efficient would require 14 kg of wood to heat a room to 68F. A modern woodstove that is 70% efficient uses 2 kg of wood to heat a room to 68F. Calculating Efficiencies Multiply efficiencies to determine overall efficiency: 0.35 x 0.90 x 0.05 = 0.01575 or 1.6% Entropy Randomness Always increasing in a system unless energy is added to create order. Energy Conversions underlie all ecological processes All living things work against entropy to maintain order Less energy available = less life to be supported Entropy: Is this a system? What happens to your room if you don’t expend energy to put things away? Where would the energy to pick up your room come from? In using food energy to clean your room, you are decreasing the entropy of your room, but Increasing the entropy in the universe by producing body heat. Connecting Laws of Matter and Energy to Environmental Problems High-throughput (high waste) economy Matter is stored as waste; continuous seeking of both matter and energy to maintain economy Matter Recycling economy Matter is conserved by recycling therefore resources are preserved; more energy maybe needed to recycle materials. Low-throughput (low waste) economy Matter and energy are both conserved; minimizing waste and energy needed to recycle or create new materials. ENERGY IS A LIMITING FACTOR IN SYSTEMS Life requires order. All living things work against entropy by using energy to maintain order. The form and amount of energy available in an environment determines what kinds of organisms can live there. Ex: Rainforest vs Arctic Tundra; photosynthesis vs chemosynthesis Energy: Limiting Factor vs vs