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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)