Chapter Overview Questions - WordPress.com · The genes in each cell are coded by sequences of...
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Chapter 2
Science, Systems, Matter, and Energy
Chapter Overview Questions
Ø What is science, and what do scientists do? Ø What are major components and behaviors
of complex systems? Ø What are the basic forms of matter, and what
makes matter useful as a resource? Ø What types of changes can matter undergo
and what scientific law governs matter?
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Chapter Overview Questions (cont’d)
Ø What are the major forms of energy, and what makes energy useful as a resource?
Ø What are two scientific laws governing changes of energy from one form to another?
Ø How are the scientific laws governing changes of matter and energy from one form to another related to resource use, environmental degradation and sustainability?
Core Case Study: Environmental Lesson from Easter
Island Ø Thriving society
l 15,000 people by 1400. Ø Used resources faster
than could be renewed l By 1600 only a few
trees remained. Ø Civilization collapsed
l By 1722 only several hundred people left.
Figure 2-1
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THE NATURE OF SCIENCE
Ø What do scientists do? l Collect data. l Form hypotheses. l Develop theories,
models and laws about how nature works.
Figure 2-2
Scientific Theories and Laws: The Most Important Results of Science
Ø Scientific Theory l Widely tested and
accepted hypothesis.
Ø Scientific Law l What we find
happening over and over again in nature.
Figure 2-3
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Testing Hypotheses
Ø Scientists test hypotheses using controlled experiments and constructing mathematical models. l Variables or factors influence natural processes l Single-variable experiments involve a control and
an experimental group. l Most environmental phenomena are
multivariable and are hard to control in an experiment.
• Models are used to analyze interactions of variables.
Scientific Reasoning and Creativity
Ø Inductive reasoning l Involves using specific observations and
measurements to arrive at a general conclusion or hypothesis.
l Bottom-up reasoning going from specific to general.
Ø Deductive reasoning l Uses logic to arrive at a specific conclusion. l Top-down approach that goes from general to
specific.
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Frontier Science, Sound Science, and Junk Science
Ø Frontier science has not been widely tested (starting point of peer-review).
Ø Sound science consists of data, theories and laws that are widely accepted by experts.
Ø Junk science is presented as sound science without going through the rigors of peer-review.
Limitations of Environmental Science
Ø Inadequate data and scientific understanding can limit and make some results controversial. l Scientific testing is based on disproving rather
than proving a hypothesis. • Based on statistical probabilities.
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MODELS AND BEHAVIOR OF SYSTEMS
Ø Usefulness of models l Complex systems are predicted by developing a
model of its inputs, throughputs (flows), and outputs of matter, energy and information.
l Models are simplifications of “real-life”. l Models can be used to predict if-then scenarios.
Feedback Loops: How Systems Respond to Change
Ø Outputs of matter, energy, or information fed back into a system can cause the system to do more or less of what it was doing. l Positive feedback loop causes a system to
change further in the same direction (e.g. erosion)
l Negative (corrective) feedback loop causes a system to change in the opposite direction (e.g. seeking shade from sun to reduce stress).
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Feedback Loops:
Ø Negative feedback can take so long that a system reaches a threshold and changes. l Prolonged delays may prevent a negative
feedback loop from occurring. Ø Processes and feedbacks in a system can
(synergistically) interact to amplify the results. l E.g. smoking exacerbates the effect of asbestos
exposure on lung cancer.
TYPES AND STRUCTURE OF MATTER
Ø Elements and Compounds l Matter exists in chemical forms as elements and
compounds. • Elements (represented on the periodic table) are the
distinctive building blocks of matter. • Compounds: two or more different elements held
together in fixed proportions by chemical bonds.
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Atoms
Figure 2-4
Ions
Ø An ion is an atom or group of atoms with one or more net positive or negative electrical charges.
Ø The number of positive or negative charges on an ion is shown as a superscript after the symbol for an atom or group of atoms l Hydrogen ions (H+), Hydroxide ions (OH-) l Sodium ions (Na+), Chloride ions (Cl-)
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Ø The pH (potential of Hydrogen) is the concentration of hydrogen ions in one liter of solution.
Figure 2-5
Compounds and Chemical Formulas
Ø Chemical formulas are shorthand ways to show the atoms and ions in a chemical compound. l Combining Hydrogen ions (H+) and Hydroxide
ions (OH-) makes the compound H2O (dihydrogen oxide, a.k.a. water).
l Combining Sodium ions (Na+) and Chloride ions (Cl-) makes the compound NaCl (sodium chloride a.k.a. salt).
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Organic Compounds: Carbon Rules
Ø Organic compounds contain carbon atoms combined with one another and with various other atoms such as H+, N+, or Cl-.
Ø Contain at least two carbon atoms combined with each other and with atoms. l Methane (CH4) is the only exception. l All other compounds are inorganic.
Organic Compounds: Carbon Rules
Ø Hydrocarbons: compounds of carbon and hydrogen atoms (e.g. methane (CH4)).
Ø Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms (e.g. DDT (C14H9Cl5)).
Ø Simple carbohydrates: certain types of compounds of carbon, hydrogen, and oxygen (e.g. glucose (C6H12O6)).
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Cells: The Fundamental Units of Life
Ø Cells are the basic structural and functional units of all forms of life. l Prokaryotic cells
(bacteria) lack a distinct nucleus.
l Eukaryotic cells (plants and animals) have a distinct nucleus.
Figure 2-6
Fig. 2-6a, p. 37
(a) Prokaryotic Cell
Protein construction and energy conversion occur without specialized internal structures
Cell membrane (transport of raw materials and finished products)
DNA (information storage, no nucleus)
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Fig. 2-6b, p. 37
Protein construction
(b) Eukaryotic Cell
Cell membrane (transport of raw materials and finished products) Packaging
Energy conversion
Nucleus (information storage)
Macromolecules, DNA, Genes and Chromosomes Ø Large, complex organic
molecules (macromolecules) make up the basic molecular units found in living organisms. l Complex carbohydrates l Proteins l Nucleic acids l Lipids
Figure 2-7
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Fig. 2-7, p. 38
The genes in each cell are coded by sequences of nucleotides in their DNA molecules.
A human body contains trillions of cells, each with an identical set of genes.
There is a nucleus inside each human cell (except red blood cells).
Each cell nucleus has an identical set of chromosomes, which are found in pairs.
A specific pair of chromosomes contains one chromosome from each parent.
Each chromosome contains a long DNA molecule in the form of a coiled double helix.
Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life.
States of Matter
Ø The atoms, ions, and molecules that make up matter are found in three physical states: l solid, liquid, gaseous.
Ø A fourth state, plasma, is a high energy mixture of positively charged ions and negatively charged electrons. l The sun and stars consist mostly of plasma. l Scientists have made artificial plasma (used in
TV screens, gas discharge lasers, florescent light).
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Matter Quality
Ø Matter can be classified as having high or low quality depending on how useful it is to us as a resource. l High quality matter is
concentrated and easily extracted.
l low quality matter is more widely dispersed and more difficult to extract.
Figure 2-8
Fig. 2-8, p. 39
High Quality Low Quality
Salt
Solid Gas
Coal Coal-fired power plant emissions
Gasoline Automobile emissions
Solution of salt in water
Aluminum ore Aluminum can
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CHANGES IN MATTER Ø Matter can change from one physical form to
another or change its chemical composition. l When a physical or chemical change occurs, no
atoms are created or destroyed. • Law of conservation of matter.
l Physical change maintains original chemical composition.
l Chemical change involves a chemical reaction which changes the arrangement of the elements or compounds involved.
• Chemical equations are used to represent the reaction.
Chemical Change
Ø Energy is given off during the reaction as a product.
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p. 39
Reactant(s) Product(s)
carbon + oxygen carbon dioxide + energy
C + O2 CO2 energy +
energy +
black solid colorless gas colorless gas
+
Types of Pollutants
Ø Factors that determine the severity of a pollutant’s effects: chemical nature, concentration, and persistence.
Ø Pollutants are classified based on their persistence: l Degradable pollutants l Biodegradable pollutants l Slowly degradable pollutants l Nondegradable pollutants
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Nuclear Changes: Radioactive Decay Ø Natural radioactive decay: unstable isotopes
spontaneously emit fast moving chunks of matter (alpha or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. l Radiation is commonly used in energy production
and medical applications. l The rate of decay is expressed as a half-life (the
time needed for one-half of the nuclei to decay to form a different isotope).
Nuclear Changes: Fission
Ø Nuclear fission: nuclei of certain isotopes with large mass numbers are split apart into lighter nuclei when struck by neutrons.
Figure 2-9
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Uranium-235
Uranium-235
Uranium-235
Uranium-235
Uranium-235
Uranium-235
Uranium-235
Uranium-235
Uranium-235 Fig. 2-6, p. 28
Neutron
Uranium-235
Energy
Fission fragment
Fission fragment
n
n
n
n
n
n
Energy
Energy
Energy
Stepped Art
Nuclear Changes: Fusion
Ø Nuclear fusion: two isotopes of light elements are forced together at extremely high temperatures until they fuse to form a heavier nucleus.
Figure 2-10
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Fig. 2-10, p. 42
Neutron
+
Hydrogen-2 (deuterium nucleus)
Hydrogen-3 (tritium nucleus)
+
Proton Neutron
100 million °C
Energy
+
Helium-4 nucleus
Products Reaction
Conditions Fuel
+
ENERGY
Ø Energy is the ability to do work and transfer heat. l Kinetic energy – energy in motion
• heat, electromagnetic radiation l Potential energy – stored for possible use
• batteries, glucose molecules
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Electromagnetic Spectrum
Ø Many different forms of electromagnetic radiation exist, each having a different wavelength and energy content.
Figure 2-11
Fig. 2-11, p. 43
Sun
Nonionizing radiation Ionizing radiation
High energy, short Wavelength
Wavelength in meters (not to scale)
Low energy, long Wavelength
Cosmic rays
Gamma Rays
X rays Far
infrared waves
Near ultra- violet waves
Visible Waves
Near infrared waves
Far ultra- violet waves
Micro- waves
TV waves
Radio Waves
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Electromagnetic Spectrum
Ø Organisms vary in their ability to sense different parts of the spectrum.
Figure 2-12
Fig. 2-13, p. 44
Low-temperature heat (100°C or less) for space heating
Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing
steam, electricity, and hot water
Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)
Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity
Dispersed geothermal energy Low-temperature heat (100°C or lower)
Normal sunlight Moderate-velocity wind High-velocity water flow Concentrated geothermal energy Moderate-temperature heat
(100–1,000°C) Wood and crop wastes
High-temperature heat (1,000–2,500°C) Hydrogen gas Natural gas Gasoline Coal Food
Electricity Very high temperature heat (greater than 2,500°C) Nuclear fission (uranium) Nuclear fusion (deuterium) Concentrated sunlight High-velocity wind
Source of Energy Relative Energy Quality
(usefulness)
Energy Tasks
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ENERGY LAWS: TWO RULES WE CANNOT BREAK
Ø The first law of thermodynamics: we cannot create or destroy energy. l We can change energy from one form to another.
Ø The second law of thermodynamics: energy quality always decreases. l When energy changes from one form to another,
it is always degraded to a more dispersed form. l Energy efficiency is a measure of how much
useful work is accomplished before it changes to its next form.
Fig. 2-14, p. 45
Chemical energy (food)
Solar energy
Waste Heat
Waste Heat
Waste Heat
Waste Heat
Mechanical energy
(moving, thinking,
living)
Chemical energy
(photosynthesis)
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SUSTAINABILITY AND MATTER AND ENERGY LAWS
Ø Unsustainable High-Throughput Economies: Working in Straight Lines l Converts resources to goods in a manner that
promotes waste and pollution.
Figure 2-15
Fig. 2-15, p. 46
High-quality energy Matter
Unsustainable high-waste economy
System Throughputs
Inputs (from environment)
Outputs (into environment)
Low-quality energy (heat) Waste and pollution
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Sustainable Low-Throughput Economies: Learning from Nature
Ø Matter-Recycling-and-Reuse Economies: Working in Circles l Mimics nature by recycling and reusing, thus
reducing pollutants and waste. l It is not sustainable for growing populations.
Fig. 2-16, p. 47
Recycle and
reuse
Low-quality Energy (heat)
Waste and
pollution Pollution control
Sustainable low-waste economy
Waste and
pollution
Matter Feedback
Energy Feedback
Inputs (from environment)
Energy conservation
Matter
Energy
System Throughputs
Outputs (into environment)