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Transcript
Living in the Environment 16th Edition Chapter 2 Science, Systems, Matter, and Energy Key Concepts Science as a process for understanding Components and regulation of systems Matter: forms, quality, and how it changes; laws of matter Energy: forms, quality, and how it changes; laws of energy Nuclear changes and radioactivity Science, and Critical Thinking Scientific data Ask a question Facts Scientific hypothesis Explanation of what is observed in nature Scientific (natural) laws Scientific theories Consensus science Data, theories, and laws that widely accepted by the scientific community Frontier science Preliminary results Do experiments and collect data Interpret data Formulate hypothesis to explain data Well-tested and accepted patterns In data become scientific laws Do more Experiments to test hypothesis Revise hypothesis if necessary Well-tested and accepted hypotheses become scientific theories Scientific Method Make Observations Formulate a Hypothesis Test Hypothesis Collect Data Interpret Data Draw Conclusions Controlled Experiment (Single Variable Analysis) • Experimental Group – Variables change in a known way – Independent variable – Dependent Variable • Control Group (Controls) – Variables are not changed • Controls • Constants • Data – Quantitative - numbers – Qualitative - descriptions Types of Reasoning • Inductive reasoning – Using specific observations and measurements to arrive at a general conclusion – bottom-up reasoning • Deductive reasoning – Reasoning that goes from the general to the specific – top-down reasoning Models and Behavior of Systems System – a set of components that 1) function in a regular and predictable manner 2) can be isolated for observation and study Models and Behavior of Systems • Inputs – matter, energy, information • Flows – throughputs of matter, energy, or information at certain rates • Stores – storage areas for matter, energy or information • Outputs – Form of matter, energy, or information that flow out of the system and into sinks in the environment Models Approximate representations or simulations of real systems to – find out how systems work – evaluate which ideas or hypotheses work • Mental models – what do you think • Mathematical models – one or more equations – To describe the behavior of a system – Make predictions about the behavior of a system • Conceptual models – Qualitative • Numerical models – Computer simulations System Regulation Feedback loop – when output of matter, energy, or information is fed back into the system as an input that changes the system. • Positive Feedback – causes change in the same direction • Negative Feedback – one change leads to a lessoning of that change. Coupled loops System Regulation • Homeostasis – maintenance of a favorable internal condition of a system despite external changes. • Time Delay – delay in expected effect • Synergy – the combined effect of two or more processes is greater than the sum of the separate effects Matter: Forms, Structure, and Quality • Elements – Building blocks of matter • Compounds – Two or more different elements held together by chemical bonds • Mixtures – Combinations of various elements, compounds, or both • Molecules – Two or more atoms of the same or different elements held together by chemical bonds – Example: O2 Atom – the smallest unit of matter that is unique to a particular element. Subatomic Particles • Protons – Positively charges • Neutrons – uncharged • Electrons – Negatively charged Atomic Characteristics • Atomic Number – Number of protons in the nucleus • Atomic Mass – Number of protons and neutrons • Ions – Atoms that have lost or gained electrons • Isotopes – Forms of a element having the same atomic number but a different mass number – Identified by attaching their mass number to their name – U235 Examples of Atoms Chemical Bonds • Chemical formulas show the number of atoms of each type in a compound – Contains symbol for each element – Uses subscripts to represent the number of atoms • Ionic bonds – Bonds between oppositely charged ions – NaCl (Na+ and Cl-) Chemical Bonds • Covalent bonds – bonds between uncharged atoms – H2O • Hydrogen bonds – Weak attraction between molecules of covalent compounds Organic vs Inorganic Compounds Organic compounds –contain carbon atoms –Held together by covalent bonds • Hydrocarbons – Carbon and hydrogen – methane (CH3) • Chlorinated hydrocarbons – Carbon, hydrogen, and chlorine – DDT (C14H9Cl5) • Chlorofluorocarbons (CFCs) – Carbon, chlorine, and flourine – freon (CCl2F2) Organic Compounds • Simple carbohydrates – Carbon, hydrogen, oxygen – Simple sugars (C6H12O6) • Complex carbohydrates – Two or more simple sugars hooked together • Proteins – Monomers of amino acids linked together Genetic Material •Nucleic Acids DNA and RNA •Genes – specific sequence of nucleotides in a DNA molecule Organic vs Inorganic Compounds Inorganic compounds – Lack carbon-carbon or carbonhydrogen covalent bonds – NaCl, H2O, N2O, CO2, NH3 The Four States of Matter Solid Liquid Gas Plasma The Four States of Matter Plasma high energy mixture of positively charged ions and negatively charged electrons sun, stars, lightening Matter Quality and Material Efficiency • High-quality matter – Concentrated – Near the earth’s surface – Great potential for use • Low-quality matter – Dilute – Deep underground – Little potential as a resource • Material efficiency (resource productivity) – Total amount of material needed to produce each unit of goods and services Energy: What is it? The capacity to do work and transfer heat. Work = force x distance Energy: Forms • Kinetic energy – Energy contained in moving objects – Wind, streams, electricity • Potential energy – Stored energy – Stick of dynamite, water behind a dam Electromagnetic radiation Energy radiated in the form of waves as a result of changing electric and magnetic fields Heat Energy • Heat – The total kinetic energy of all the moving atoms, ions, or molecules within a given substance • Temperature – Average speed of motion of the atoms, ions, or molecules in a sample of matter at a given moment Transfer of Heat Energy Convection Conduction Heating water in the bottom of a pan causes some of the water to vaporize into bubbles. Because they are lighter than the surrounding water, they rise. Water then sinks from the top to replace the rising bubbles.This up and down movement (convection) eventually heats all of the water. Radiation Heat from a stove burner causes atoms or molecules in the pan’s bottom to vibrate faster. The vibrating atoms or molecules then collide with nearby atoms or molecules, causing them to vibrate faster. Eventually, molecules or atoms in the pan’s handle are vibrating so fast it becomes too hot to touch. As the water boils, heat from the hot stove burner and pan radiate into the surrounding air, even though air conducts very little heat. Energy: Quality High-quality energy concentrated Low-quality energy dispersed Physical and Chemical Changes The Law of Conservation of Matter: matter is neither created nor destroyed Matter is not consumed Matter only changes form There is no “away” How harmful are pollutants? 1) Chemical nature of pollutants 2) Concentration 3) Persistence – Degradable (nonpersistent) pollution • Broken down completely by natural, chemical or biological processes – Slowly degradable (persistent) pollution • • May take decades or longer DDT – Nondegradable pollutants • • Cannot be broken down Lead, mercury, arsenic Nuclear Changes – nuclei of isotopes spontaneously change 1) Natural radioactive decay • Unstable isotopes spontaneously emit fast-moving particles, high energy radiation, or both at fixed rates • “radioisotopes” • Damaging “ionizing” radiation Ionizing Radiation 1) Gamma rays • High-energy electromagnetic radiation 2) Alpha particles • Fast moving, positively charged chunks of matter 3) Beta particles • High speed electrons Ionizing Radiation: Effects • Genetic Damage • • Mutations or changes in DNA that alter genes and chromosomes Somatic Damage to tissue • Burns, eye cataracts, certain cancers Nuclear Changes Radioactive Decay • Radioactive isotopes decay at a characteristic fixed rate called a half-life (t1/2) – Time for half the nuclei in a sample to decay – Can’t be changed due to T, P, or chemical rxns – Used to estimate time a sample of radioisotope must be stored safely before it decays to a safe level half-life X 10 Radioactive Decay and Half-life • Time needed for onehalf of the nuclei in a radioisotope to emit its radiation (decay) • Characteristic half-life for each radioisotope • General rule: radioisotopes must be stored for 10 half-lives Half-Lives of Selected Radioisotopes Isotope Radiation Half-Life Emmitted Potassuium42 12.4 hrs Alpha, beta Iodine-131 8 days Beta, gamma Colbalt-60 5.27 yrs Beta, gamma Hydogren-3 tritium 12.5 yrs Beta Strontium-90 28 yrs Beta Carbon-14 5,370 yrs Beta Plutonium-239 24,000 hrs Alpha, gamma Uranium-235 710 million yrs Alpha, gamma Uranium-238 4.5 billion yrs Alpha, gamma Nuclear Reactions Fission Fusion Nuclear Changes Nuclear Fission • Fission—splitting of nuclei – Nuclei of isotopes with large masses split into lighter nuclei when struck by neutrons – Release energy and more neutrons setting off a chain reaction – Atomic bomb and nuclear power plants 235 92 U n 92 36 Kr n 235 92 U 92 36 Kr 235 92 U n n 141 Ba 56 n 92 Kr 36 n n n n 235 92 U n 141 56 Ba 141 Ba 56 92 Kr n 36 235 92 U n 141 Ba 56 23 5 U 92 n 235 92 U Nuclear Changes Nuclear Fusion • Fusion—joining of nuclei – Isotopes of light elements are forced together at high T’s until they fuse into a heavier nucleus • Harder to accomplish than fission, but releases more energy • Fusion of H nuclei to form He nuclei is a source of energy for sun and stars • H bombs Fuel Reaction Conditions Products D-T Fusion Neutron + Hydrogen-2 or deuterium nucleus + Hydrogen-3 or tritium nucleus + Proton Neutron + + 100 million ˚C Energy + + Helium-4 nucleus Laws Governing Energy Changes First Law of Thermodynamics (Energy) Energy is neither created nor destroyed Energy only changes form You can’t get something for nothing ENERGY IN = ENERGY OUT Laws Governing Energy Changes Second Law of Thermodynamics In every transformation, some energy is converted to heat You cannot break even in terms of energy quality Solar energy Waste heat Mechanical energy (moving, thinking, living) Chemical energy (food) Chemical energy (photosynthesis) Waste heat Waste heat Waste heat Connections: Matter and Energy Laws and Environmental Problems High-throughput (waste) economy Matter-recycling economy Low-throughput economy