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Science, Systems, Matter, and Energy

What do scientists do?Collect data.

Form hypotheses.

Develop theories, models

and laws about how nature

works.

Scientific TheoryWidely tested and

accepted hypothesis.

Scientific LawWhat we find

happening over and

over again in nature.

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Scientists test hypotheses using controlled

experiments and constructing

mathematical models.Variables or factors influence natural processes

Single-variable experiments involve a control and

an experimental group.

Most environmental phenomena are

multivariable and are hard to control in an

experiment.

Models are used to analyze interactions of variables.

Inductive reasoningInvolves using specific observations and

measurements to arrive at a general conclusion or

hypothesis.

Bottom-up reasoning going from specific to

general.

Deductive reasoningUses logic to arrive at a specific conclusion.

Top-down approach that goes from general to

specific.

Frontier science has not been widely tested

(starting point of peer-review).

Sound science consists of data, theories and

laws that are widely accepted by experts.

Junk science is presented as sound science

without going through the rigors of peer-

review.

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Usefulness of modelsComplex systems are predicted by developing a

model of its inputs, throughputs (flows), and outputs

of matter, energy and information.

Models are simplifications of “real-life”.

Models can be used to predict if-then scenarios.

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.Positive feedback loop causes a system to change

further in the same direction (e.g. erosion)

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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Negative feedback can take so long that a

system reaches a threshold and changes.Prolonged delays may prevent a negative

feedback loop from occurring.

Processes and feedbacks in a system can

(synergistically) interact to amplify the

results.E.g. smoking exacerbates the effect of asbestos

exposure on lung cancer.

Elements and CompoundsMatter 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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An ion is an atom or group of atoms with

one or more net positive or negative

electrical charges.

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 Hydrogen ions (H+), Hydroxide ions (OH-)

Sodium ions (Na+), Chloride ions (Cl-)

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The pH (potential of Hydrogen) is the

concentration of hydrogen ions in one liter of

solution.

Figure 2-5

Chemical formulas are shorthand ways to

show the atoms and ions in a chemical

compound. Combining Hydrogen ions (H+) and Hydroxide ions

(OH-) makes the compound H2O (dihydrogen

oxide, a.k.a. water).

Combining Sodium ions (Na+) and Chloride ions

(Cl-) makes the compound NaCl (sodium chloride

a.k.a. salt).

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Organic compounds contain carbon atoms

combined with one another and with

various other atoms such as H+, N+, or Cl-.

Contain at least two carbon atoms

combined with each other and with atoms.Methane (CH4) is the only exception.

All other compounds are inorganic.

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Hydrocarbons: compounds of carbon and

hydrogen atoms (e.g. methane (CH4)).

Chlorinated hydrocarbons: compounds

of carbon, hydrogen, and chlorine atoms

(e.g. DDT (C14H9Cl5)).

Simple carbohydrates: certain types of

compounds of carbon, hydrogen, and

oxygen (e.g. glucose (C6H12O6)).

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The atoms, ions, and molecules that make up matter are found in three physical states:solid, liquid, gaseous.

A fourth state, plasma, is a high energy mixture of positively charged ions and negatively charged electrons.The sun and stars consist mostly of plasma.

Scientists have made artificial plasma (used in TV screens, gas discharge lasers, florescent light).

Matter can be classified as having high or low quality depending on how useful it is to us as a resource.High quality matter is

concentrated and easily extracted.

low quality matter is more widely dispersed and more difficult to extract.

High Quality Low Quality

Salt

Solid Gas

Coal Coal-fired power plant emissions

GasolineAutomobile emissions

Solution of salt in water

Aluminum oreAluminum can

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Matter can change from one physical form to another or change its chemical composition.When a physical or chemical change occurs, no

atoms are created or destroyed. Law of conservation of matter.

Physical change maintains original chemical composition.

Chemical change involves a chemical reaction which changes the arrangement of the elements or compounds involved. Chemical equations are used to represent the reaction.

Energy is given off during the reaction as a product.

Cells are the basic

structural and functional

units of all forms of life.Prokaryotic cells (bacteria)

lack a distinct nucleus.

Eukaryotic cells (plants

and animals) have a

distinct nucleus.

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Large, complex organic

molecules (macromolecules)

make up the basic molecular

units found in living

organisms.Complex carbohydrates

Proteins

Nucleic acids

Lipids

Factors that determine the severity of a pollutant’s effects: chemical nature, concentration, and persistence.

Pollutants are classified based on their persistence:Degradable pollutants

Biodegradable pollutants

Slowly degradable pollutants

Nondegradable pollutants

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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.Radiation is commonly used in energy production and

medical applications.

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).

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Nuclear fission: nuclei of certain isotopes

with large mass numbers are split apart

into lighter nuclei when struck by neutrons.

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Neutron

Uranium-235

Energy

Fission

fragment

Fission

fragment

n

n

n

n

n

n

Energy

Energy

Energy

Nuclear fusion: two isotopes of light elements are forced together at extremely high temperatures until they fuse to form a heavier nucleus.

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Neutron

+

Hydrogen-2

(deuterium nucleus)

Hydrogen-3

(tritium nucleus)

+

Proton Neutron

100

million °C

Energy

+

Helium-4 nucleus

ProductsReaction

ConditionsFuel

+

Energy is the ability to do work and transfer

heat.Kinetic energy – energy in motion

heat, electromagnetic radiation

Potential energy – stored for possible use

batteries, glucose molecules

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Many different forms of electromagnetic

radiation exist, each having a different

wavelength and energy content.

Organisms vary

in their ability to

sense different

parts of the

spectrum.

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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 movevehicles and other things)

High-temperature heat(1,000–2,500°C) forindustrial processes andproducing electricity

Dispersed geothermal energyLow-temperature heat

(100°C or lower)

Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat

(100–1,000°C)Wood and crop wastes

High-temperature heat(1,000–2,500°C)

Hydrogen gasNatural gasGasolineCoalFood

ElectricityVery high temperature heat(greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind

Source of Energy Relative

Energy Quality

(usefulness)

Energy Tasks

The first law of thermodynamics: we cannot create or destroy energy.We can change energy from one form to another.

The second law of thermodynamics: energy quality always decreases.When energy changes from one form to another, it

is always degraded to a more dispersed form.

Energy efficiency is a measure of how much useful work is accomplished before it changes to its next form.

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Chemical

energy

(food)

Solar

energy

Waste

Heat

Waste

HeatWaste

Heat

Waste

Heat

Mechanical

energy

(moving,

thinking,

living)

Chemical

energy

(photosynthesis)

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Matter-Recycling-and-Reuse Economies:

Working in CirclesMimics nature by recycling and reusing, thus reducing

pollutants and waste.

It is not sustainable for growing populations.

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