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Chapter 3

Chapter 3. Science, Systems, Matter and Energy. What is Energy? The capacity to do work and transfer heat. Potential Energy Stored and potentially available for use. Kinetic Energy Matter has because of its mass and speed. Potential energy can be changed to kinetic energy!.

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Chapter 3

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  1. Chapter 3 Science, Systems, Matter and Energy

  2. What is Energy?The capacity to do work and transfer heat • PotentialEnergyStored and potentially available for use • Kinetic EnergyMatter has because of its mass and speed Potential energy can be changed to kinetic energy!

  3. Electromagnetic Radiation Energy radiated in the form of a wave as a result of changing electric and magnetic fields

  4. What is Heat and How is it Transferred? The total kinetic energy of all moving atoms, ions, molecules in a given substance

  5. What is Energy Quality? A measure of an energy source’s ability to do useful work Industrial processesProducing electricity to run lights, motors Mechanical motion Industrial processesProducing electricity Moderate-temp heat for industrial processes, cooking, steam, electricity Low-temp heat for space heating

  6. Physical vs. Chemical Change Physical Change Chemical Change • No change in chemical composition • Composition of the elements or compounds are altered

  7. Law of Conservation of Matter We may change various elements and compounds from one physical or chemical form to another, but we cannot create or destroy any of the atoms involved There is really no AWAY in “to throw away”

  8. 3 Factors Determining Pollutant’s Harmful Effects • Chemical Nature • Concentration: 1 part pollutant to how ever many parts of gas, liquid or mixture pollutant is found in • Parts per million (ppm) • Parts per billion (ppb) • Parts per trillion (ppt)

  9. 3 Factors Determining Pollutant’s Harmful Effects • Persistence: how long it stays in the air, water, soil or body • Degradable (non-persistent): broken down completely or reduced to acceptable levels by natural physical, chemical, and biological processes • Human sewage in a river, degrades quickly by bacteria • Slowly degradable (persistent): take decades or longer to degrade • Insecticide and most plastics • Nondegradable: cannot be broken down by natural processes • Toxic elements such as lead, mercury, arsenic

  10. Nuclear Change • Natural Radioactive Decay • Unstable isotope emits a fast-moving particle, high-energy radiation, or both • Decay continues into various isotopes until original is changed into a stable isotope Gamma rays are most common form of ionizing radiation emitted Alpha particles: fast moving, positively charged, 2 protons + 2 neutrons Beta particles: high-speed electrons

  11. Nuclear Change • Nuclear Fission • Nuclei of certain isotopes with large mass numbers (Uranium-235) are split apart into lighter nuclei when struck by neutrons • Critical Mass: enough fissionable material is present for multiple fissions to occur forming a chain reaction

  12. Nuclear Change • Nuclear Fusion • Two isotopes of light elements are forced together at extremely high temperatures until they fuse • Form a heavier nucleus, releasing energy • Requires temp of at least 100 million °C • More difficult to initiate, but releases much more energy per unit than fission

  13. Radiation Exposure • What are some sources of radiation you come into contact with frequently? • http://abcnews.go.com/Health/radiation-exposure-things/story?id=13131122 • What are the effects of ionizing radiation? • Genetic damage • Somatic damage

  14. First Law of Thermodynamics Also known as the Law of Conservation of Energy Energy cannot be created or destroyed, only converted from one form to another When one form of energy is converted to another form (physical or chemical change) the energy input = output You cannot get something from nothing

  15. Second Law of Thermodynamics Burning gas in a car or using up a battery, something has been lost. If it isn’t energy what is it? Energy Quality: amount of energy available to do useful work When energy is changed from one form to another there is ALWAYS a decrease in energy quality Lower quality More dispersed Less useful You cannot break even

  16. What do a car, a light bulb and food have in common?

  17. Where does the energy go? • Only ~10% high-quality energy available in gasoline’s fuel which is converted to mechanical energy • Remaining 90% degraded to low-quality heat, release to space • Electrical flow through filament changed to 5% useful light • Remaining 95% low-quality heat to environment • Solar energy converted to chemical energy (plants) and then into mechanical energy (moving, living) • Your body continuously gives of heat

  18. 2nd Law of Thermodynamics Cont. • We can never recycle or reuse high-quality energy to perform useful work • Can heat air or water at low temperature to upgrade to high-quality energy • BUT it will take more energy than we can get in return • Energy use estimates in the US • 16% for useful work • 41% unavoidably wasted • 43% unnecessarily wasted

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