chapter 2 critical thinking: science, models, & systems tutorial by paul rich © brooks/cole...

Chapter 2Chapter 2

Critical Thinking:Critical Thinking:Science, Models, & SystemsScience, Models, & Systems

tutorial by Paul Rich

© Brooks/Cole Publishing Company / ITP

OutlineOutline

1. Science & Technology• What is science?• What is technology?• scientific process

2. Systems• What is a system?• inputs, throughputs, & outputs• feedback loops• behavior of complex systems


1. Science & Technology1. Science & Technology

• Science• pursuit of knowledge about how the world works

• some basic assumptions:– there is order in the universe– human mind is capable of comprehending this order– if conditions are the same the results will be the same

• Technology• creation of new products & processes intended to

improve survival, comfort, or quality of life

Scientific Laws & TheoriesScientific Laws & Theories• Scientific Law• a basic underlying principle that matter, energy, &

certain other phenomena apparently always act (or react) in a predictable manner

• (e.g., the law of gravity)

• Theory• a conceptual formulation which provides a

rational explanation or framework for numerous related observations

• (e.g., global warming due to greenhouse effect)

Hypotheses & ScienceHypotheses & Science

• Hypothesis• a tentative explanation; an educated guess

• some characteristics: • good hypotheses are falsifiable • falsifiable: a premise that can potentially be shown

to be incorrect or false • science proceeds by rejection of hypotheses • no such thing as final proof

Scientific ProcessScientific Process• hypotheses proposed to explain observed patterns• critical tests or experiments conducted• a hypothesis supported by a great deal of evidence

becomes a scientific theory

Accuracy vs. PrecisionAccuracy vs. Precision• Accuracy: extent to which a measurement agrees

with the accepted or correct value• Precision: measure of reproducibility

Types of ReasoningTypes of Reasoning• deductive reasoning:

• inductive reasoning:

• reductionism:

• holism:

• scientific approach in which processes are explained by understanding the parts, e.g., functioning of an organism understood by looking at biochemistry.

• scientific approach in which processes are explained by looking at all levels of organization, accounting for emergent processes.

• reasoning from a theory or principle to an unknown; goes from general to specific.

• reasoning from a series of facts or cases to general principles or theories; goes from specific to general.

2. Systems2. Systems• System: a set of components that function &

interact in some regular or predictable manner• structure –– the organization of system

components• function –– what the system does• e.g., circulatory system –– natural system

(components: heart, arteries, veins, capillaries, & blood) that moves blood through body (function: transport of oxygen, carbon dioxide, & nutrients)

• e.g., automobile –– human–made system (components: engine, body, brakes, wheels, etc.) that serves to move people & objects (function: transportation)


Inputs, Throughputs, & OutputsInputs, Throughputs, & Outputsmatter, energy, & information flow in (input), through (throughput), & out (output) of a system

Fig. 2–6

Feedback LoopsFeedback Loops• Feedback Loop:

• Positive Feedback Loop:

• Negative Feedback Loop:

• Homeostasis:

• a change in a certain direction within a system causes more change in that same direction; ultimately unstable, eg., exponential growth.

• the maintenance of internal conditions despite fluctuations in external conditions, e.g., maintenance of temperature of an organism.

• a change in a certain direction within a system causes lessening of change in that same direction; ultimately stable.

• a relationship in which a change in one part of a system influences another part of the system in a way that either reinforces or slows the original change.

Positive Feedback LoopsPositive Feedback LoopsExample: exponential population growth involves a

positive feedback loop in which more individuals lead to increased numbers of births.

Negative Feedback LoopsNegative Feedback LoopsExample: temperature regulation in humans involves

a negative feedback loop in which increased temperature leads to decrease in temperature by sweating.


Behavior of Complex SystemsBehavior of Complex Systems

Fig. 2–11

Example: population dynamics of three moth species display very different patterns. It is not known whether the observed patterns are caused by chaotic behavior or orderly behavior not yet sufficiently understood.

Behavior of Complex SystemsBehavior of Complex Systems

• Example: population dynamics of three moth species display very different patterns.

• It is not known whether the observed patterns are caused by chaotic behavior or orderly behavior not yet sufficiently understood.


Complex SystemsComplex SystemsSome Important Behaviors:

• Time lags result when a change in a system leads to other changes after a delay, e.g., lung cancer after 20–30 years of smoking, global warming after decades of carbon dioxide emission.

• Resistance to change when a system has negative feedbacks that tend to maintain the system, e.g., many economic & political systems.

• Synergy results when two or more processes interact to that the combined effect is more than the sum of their separate effects, e.g., team efforts using multiple talents.

• Chaos results when noisy or unpredictable behavior is generated from within the system itself, e.g., waves in the ocean, day–to–day variation in weather.

Complex SystemsComplex Systems• Time lags

• Resistance to change

• Synergy

• Chaos

• Leverage

• results when noisy or unpredictable behavior is generated from within the system itself, e.g., waves in the ocean, day–to–day variation in weather.

• when a system has negative feedbacks that tend to maintain the system, e.g., many economic & political systems.

• results when two or more processes interact to that the combined effect is more than the sum of their separate effects, e.g., team efforts using multiple talents

• Making a small change (or incentive) to a component to yield a large improvement.

• result when a change in a system leads to other changes after a delay, e.g., lung cancer after 20–30 years of smoking, global warming after decades of carbon dioxide emission.

Science is an adventure of the human spirit. It is essentially an artistic enterprise, stimulated largely by curiosity, served largely by disciplined imagination & based largely on faith in the reasonableness, order, & beauty of the universe.––Warren Weaver

Scientific knowledge is a body of statements of varying degrees of certainty –– some most unsure, some nearly sure, & none absolutely certain.–– Richard Feynman


Recycling Lab Idea

• Dissect broken electronics to analyze percentages of each ingredient & how best to recycle these resources.

OutlineOutline

1. Matter (a primer about chemistry)• What is matter?• inorganic compounds, organic compounds, matter quality

2. Energy• What is energy?• energy quality

3. Changes of Matter• physical vs. chemical changes, conservation of matter• nuclear changes

4. Energy Laws• first law, second law


1. Matter1. Matter


matter: anything that has mass & takes up space.

forms:

1) elements: the distinct building blocks that form matter; made up of a single type of atom.

• 112 known elements (92 natural, 20 synthesized)• atoms are smallest unit of matter unique to an element

2) compounds: two or more different elements held together in fixed proportions by chemical bonds.

• molecules are combinations of two or more elements held together by chemical bonds

States of MatterStates of Matter


Fig. 3–2

AtomsAtoms• Atom

• protons

• neutrons

• Electrons

• atomic number

• Atomic mass number

• isotopes

• various forms of element that have same number of protons, but different numbers of neutrons.

• positively charged particles in nucleus

• number of protons in a nucleus; defines an element.

• uncharged particles in nucleus• fundamental unit of matter unique

to an element.• negatively charged particles

orbiting nucleus• total number of neutrons (mass =1)

& protons (mass =1); mass of electrons near 0.

IsotopesIsotopes

• What are the 3 isotopes of hydrogen?

• How do they differ?

• What are the 2 isotopes of uranium?

• How do they differ?

Periodic Table of ElementsPeriodic Table of Elements• How is the periodic table arranged horizontally?• Vertically?

Some Important ElementsSome Important Elements• What are the 8 most

common elements in the earth’s crust?

• Oxygen, 46.6%• Silicon 27.7%• Aluminum 8.1%• Iron, 5.0%• Calcium 3.6%• Sodium 2.8%• Potassium 2.6%• Magnesium 2.1%• All others 1.5%

IonsIons

ions: charged molecules formed when atoms of some elements gain or lose one or more electrons.

examples of positive ions:

Na+ sodium, Ca2+ calcium,

Fe+ iron, Al3+ aluminum

examples of negative ions:

Cl– chloride, PO43– phosphate,

SO3– sulfate


What are IONS?

Ions are charged molecules formed when atoms of some elements gain or lose one or more electrons.

• What are examples of positive ions?• Na+ sodium, Ca2+ calcium,

Fe+3 iron, Al3+ aluminum• What are examples of negative ions:• Cl– chloride, PO4

3– phosphate, SO42– sulfate

Strong Chemical BondsStrong Chemical Bonds

What are ionic bonds?

Strong bonds formed by joining oppositely charged ions, e.g., table salt (NaCl) is formed of Na+ & Cl– ions.

How do they arrange themselves?

Solid crystals of ionic compounds, such as NaCl, consist of a three–dimensional array of oppositely charged ions held together by ionic bonds.

Strong Chemical BondsStrong Chemical Bonds

What are covalent bonds?

Strong bonds formed by joining one or more uncharged atoms into molecules by sharing of electrons, e.g., water molecules (H2O).

What are some important molecules formed by covalent bonds?

Hydrogen, H2;

oxygen, O2,

nitrogen oxide, NO;

carbon monoxide, CO

More Important MoleculesMore Important Molecules

• N2 is 80% of the air.• Cl2 is a toxic gas.• HCl is in stomach

acid.• Water

Still More Important MoleculesStill More Important Molecules

• NO2 contibutes to smog

• CO2 contributes to global warming

• CH4, methane, is natural gas

• NH3, ammonia is important in fertilizers.

Yet More Important MoleculesYet More Important Molecules

• SO2 forms acid rain.

• O3 can block UV or attack your lungs.

• SO3 forms acid rain.

• H2S is the smell of rotten eggs.

Weak Chemical BondsWeak Chemical Bonds

What are hydrogen bonds?

Weak bonds between molecules containing slightly positive hydrogen & slightly negative nonmetallic atoms, in particular between water molecules.

Why are hydrogen bonds important?

Accounts for various properties of water, including high surface tension, high heat content, & excellent ability to serve as solvent of ionic compounds.


Inorganic vs. Organic MoleculesInorganic vs. Organic Molecules

inorganic molecule: compounds not originating from living sources; compounds lacking C–C & C–H bonds.

e.g., water H2O, carbon dioxide (CO2),

nitrogen gas (N2), oxygen gas (O2), ozone (O3).

organic molecule: compounds containing C–C &/or C–H bonds (natural & synthetic).

e.g., methane (CH4), sugars, starch, cellulose, proteins,

nucleic acids.


Matter QualityMatter QualityMatter quality is a measure of how useful a matter resource is for humans, based on its availability & concentration.

Fig. 3–12


2. Energy2. Energy

energy: the capacity to do work (by performing mechanical, physical, chemical, or electrical tasks), or to cause heat transfer between two objects at different temperatures.

Types:

• kinetic energy – energy of motion. e.g., a moving automobile, a rock rolling down a hill.

• potential energy – stored energy. e.g., a stretched rubber band, a rock on top of a hill, water stored behind a dam.

some kinds of kinetic energy:

• electrical – energy of moving electrons• electromagnetic radiation – form of kinetic energy

that travels as electromagnetic waves, e.g., radio waves, microwaves, visible light, ultraviolet radiation, & X–rays.

• heat – total kinetic energy of all moving atoms, ions, or molecules; temperature is measure of the motion.

some kinds of potential energy:• chemical energy – potential energy stored in chemical

bonds, e.g., energy in C–C & C–H bonds of fossil fuels.

• atomic energy – energy associated with nuclear structure, e.g., energy released by fission of Uranium–235.

EnergyEnergy


Electromagnetic RadiationElectromagnetic Radiation


Energy content of electromagnetic radiation varies in proportion to wavelength. Shorter wavelengths have higher energy content than longer wavelengths.

Fig. 3–13


Energy QualityEnergy Quality

Energy quality is a measure of how useful an energy source is for humans, in terms of its concentration & ability to perform useful work.

Fig. 3–14


3. Changes of Matter3. Changes of Matter

Physical change involves no change in chemical composition.

Chemical change or chemical reaction involves changes in the composition of compounds.

example:

C + O2 CO2 + energy

burning of fossil fuels

Conservation of MatterConservation of MatterLaw of Conservation of Matter: In chemical reaction atoms are never created, destroyed, or changed one into another; they are only rearranged to form different molecules & compounds.

• foundation of chemistry, biology, & ecology.

• implication that "there is no away" – earth has essentially all the matter it will ever have.

• in nuclear reactions atoms can be changed, e.g., fusion H to He.

• more strict formulation energy & matter are conserved because very small amounts of matter converted to energy, e.g., in nuclear reactions.


Radioactive IsotopesRadioactive Isotopes


Unstable isotopes undergo radioactive decay to form other isotopes, & in the process energy is emitted in three forms:

• alpha particles, fast–moving, 2 protons + 2 neutrons• beta particles, fast–moving, electrons• gamma rays, high–energy electromagnetic radiation

Fig. 3–15

Nuclear FissionNuclear Fissionnuclear fission: a nuclear change in which certain unstable isotopes of high mass numbers split into lighter nuclei & release energy in the process.

Fig. 3–17


Fission of a uranium–235 nucleus, initiated by a neutron.

Nuclear FissionNuclear Fissionnuclear chain reaction: multiple fissions resulting from a positive feedback loop in which each fission releases neutrons that cause more fissions to occur.

Fig. 3–18 © Brooks/Cole Publishing Company / ITP

A nuclear chain reaction.

Nuclear FusionNuclear Fusionnuclear fusion: a nuclear change in which two isotopes of light elements are forced together to form a heavier nucleus, releasing energy in the process.

Fig. 3–19 © Brooks/Cole Publishing Company / ITP

A nuclear fusion reaction in which helium (He) is formed by fusion of two hydrogen (H) nuclei; fusion in Sun is major source of energy for Earth processes.

4. Energy Laws4. Energy Laws

first law of thermodynamics: energy is neither created nor destroyed, but may be converted from one form to another.

• energy is conserved;

• implication that bookkeeping is possible, e.g., in ecological study, energy flow can be followed;

• Einstein showed energy & matter can be interconverted;

• also stated, "you can't get something for nothing", in terms of energy quantity.


Energy LawsEnergy Lawssecond law of thermodynamics: when energy is converted from one form to another, some of the useful energy is always degraded to lower–quality, more dispersed energy. Also can be stated: entropy increases.

• entropy is a measure of disorder; increased entropy means increased randomness or dispersion;

• degraded energy generally in form of heat;

• implication that continual energy input is needed to maintain a system;

• ordered systems result (e.g., living systems), even though entropy increases.


Energy LawsEnergy Laws

Does life disobey the second law of thermodynamics?

• no, requires massive energy flow to maintain life;

• order of living systems results from overall increased entropy;

All forms of life are tiny pockets of order (low entropy) maintained by creating a sea of disorder (high entropy) in their environment.


Implications for EnvironmentImplications for Environment

Conceptual model of eventually unsustainable high–waste, high–throughput societies.


Fig. 3–21

Implications for EnvironmentImplications for EnvironmentConceptual model of sustainable low–waste, low–throughput societies.


Fig. 3–22

chapter 2 critical thinking: science, models, & systems tutorial by paul rich © brooks/cole...

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