Chapter 3
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Transcript of Chapter 3
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Chapter 3Science, Systems, Matter and Energy
+What is Energy?The capacity to do work and transfer heat
Kinetic Energy
Matter has because of its mass and speed
Potential Energy
Stored and potentially available for use
Potential energy can be changed to kinetic energy!
+Electromagnetic RadiationEnergy radiated in the form of a wave as a result of changing electric and magnetic fields
+What is Heat and How is it Transferred?The total kinetic energy of all moving atoms, ions, molecules in a given substance
What is Energy Quality?A measure of an energy source’s ability to do useful
workIndustrial processesProducing electricity to run lights, motors
Mechanical motionIndustrial processesProducing electricity
Moderate-temp heat for industrial processes, cooking, steam, electricity
Low-temp heat for space heating
+ Physical vs. Chemical Change
No change in chemical composition
Composition of the elements or compounds are altered
Physical Change Chemical Change
+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”
+ 3 Factors Determining Pollutant’s Harmful Effects
1. Chemical Nature
2. 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)
+ 3 Factors Determining Pollutant’s Harmful Effects
3. 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
+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 neutronsBeta particles: high-speed electrons
+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
+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
+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
+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
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+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
+What do a car, a
light bulb and food have in
common?
+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
+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