chapter 2

LIVING IN THE ENVIRONMENT 17THMILLER/SPOOLMAN

CHAPTER 2Science, Matter, Energy, and Systems

Core Case Study: A Story About a Forest

• Hubbard Brook Experimental Forest in New Hampshire

• Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site)

• Stripped site:• 30-40% more runoff• More dissolved nutrients• More soil erosion

The Effects of Deforestation on the Loss of Water and Soil Nutrients

Fig. 2-1, p. 31

Stepped ArtFig. 2-1, p. 31

2-1 What Do Scientists Do?

• Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works.

Science Is a Search for Order in Nature (1)

• Identify a problem

• Find out what is known about the problem

• Ask a question to be investigated

• Gather data through experiments• Propose a scientific hypothesis

Science Is a Search for Order in Nature (2)

• Make testable predictions

• Keep testing and making observations

• Accept or reject the hypothesis

• Scientific theory: well-tested and widely accepted hypothesis

The Scientific Process

Fig. 2-2, p. 33

Fig. 2-2, p. 33

Identify a problem

Find out what is known about the

problem (literature search)

Ask a question to be investigated

Perform an experiment to

answer the question

and collect data

Analyze data (check for patterns)

Scientific law Well-accepted pattern in data

Propose a hypothesis to explain data

Use hypothesis to make testable

projections

Perform an experiment to

test projections

Accept hypothesis

Revise hypothesis

Make testable

projections

Test projections

Scientific theory Well-tested and widely accepted

hypothesis

Scientific theoryWell-tested andwidely accepted

hypothesis

Stepped Art

Testpredictions

Make testablepredictions

Accepthypothesis

Revisehypothesis

Perform an experimentto test predictions

Use hypothesis to make testable predictions

Propose an hypothesisto explain data

Analyze data(check for patterns)

Scientific lawWell-acceptedpattern in data

Perform an experimentto answer the question

and collect data

Ask a question to beinvestigated

Find out what is knownabout the problem(literature search)

Identify a problem

Fig. 2-2, p. 33

Testing a Hypothesis

Fig. 2-3, p. 33

Fig. 2-3, p. 33

Nothing happens when I try to turn on my flashlight.

Question: Why didn’t the light come on?

Hypothesis: Maybe the batteries are dead.

Test hypothesis with an experiment: Put in new batteries and try to turn on the flashlight.

Result: Flashlight still does not work.

New hypothesis: Maybe the bulb is burned out.

Experiment: Put in a new bulb.

Result: Flashlight works.

Conclusion: New hypothesis is verified.

Observation:

Characteristics of Science…and Scientists

• Curiosity• Skepticism• Reproducibility• Peer review• Openness to new ideas• Critical thinking• Creativity

Science Focus: Easter Island: Revisions to a Popular Environmental Story

• Some revisions to a popular environmental story• Polynesians arrived about 800 years ago• Population may have reached 3000• Used trees in an unsustainable manner, but rats

may have multiplied and eaten the seeds of the trees

Stone Statues on Easter Island

Fig. 2-A, p. 35

Scientific Theories and Laws Are the Most Important Results of Science

• Scientific theory• Widely tested• Supported by extensive evidence• Accepted by most scientists in a particular area

• Scientific law, law of nature

The Results of Science Can Be Tentative, Reliable, or Unreliable

• Tentative science, frontier science

• Reliable science

• Unreliable science

Science Has Some Limitations

1. Particular hypotheses, theories, or laws have a high probability of being true while not being absolute

2. Bias can be minimized by scientists

3. Environmental phenomena involve interacting variables and complex interactions

4. Statistical methods may be used to estimate very large or very small numbers

5. Scientific process is limited to the natural world

Science Focus: Statistics and Probability

• Statistics• Collect, organize, and interpret numerical data

• Probability• The chance that something will happen or be

valid• Need large enough sample size

2-2 What Is Matter?

• Concept 2-2 Matter consists of elements and compounds, which are in turn made up of atoms, ions, or molecules.

Matter Consists of Elements and Compounds

• Matter• Has mass and takes up space

• Elements• Unique properties• Cannot be broken down chemically into other

substances

• Compounds• Two or more different elements bonded together

in fixed proportions

Gold and Mercury Are Chemical Elements

Fig. 2-4a, p. 38

Chemical Elements Used in The Book

Table 2-1, p. 38

Atoms, Ions, and Molecules Are the Building Blocks of Matter (1)

• Atomic theory• All elements are made of atoms

• Subatomic particles• Protons with positive charge and neutrons with no charge

in nucleus• Negatively charged electrons orbit the nucleus

• Atomic number• Number of protons in nucleus

• Mass number • Number of protons plus neutrons in nucleus

Model of a Carbon-12 Atom

Fig. 2-5, p. 39

Fig. 2-5, p. 39

6 protons

6 neutrons

6 electrons


• Isotopes• Same element, different number of protons

• Ions• Gain or lose electrons• Form ionic compounds

• pH• Measure of acidity• H+ and OH-

Chemical Ions Used in This Book

Table 2-2, p. 40

pH Scale

Supplement 5, Figure 4

Loss of NO3− from a Deforested Watershed

Fig. 2-6, p. 40

Fig. 2-6, p. 40

Undisturbed (control) watershed

Disturbed (experimental) watershedN

itrat

e (N

O3– )

conc

entr

atio

n(m

illig

ram

s pe

r lite

r)

Year

1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

40

60

20


• Molecule• Two or more atoms of the same or different

elements held together by chemical bonds

• Compounds

• Chemical formula

Compounds Used in This Book

Table 2-3, p. 40

Organic Compounds Are the Chemicals of Life

• Organic compounds• Hydrocarbons and chlorinated hydrocarbons• Simple carbohydrates• Macromolecules: complex organic molecules

• Complex carbohydrates• Proteins• Nucleic acids• Lipids

• Inorganic compounds

Glucose Structure

Supplement 4, Fig. 4

Amino Acids and Proteins


Nucleotide Structure in DNA and RNA


DNA Double Helix Structure and Bonding


Fatty Acid Structure and Trigyceride


Matter Comes to Life through Genes, Chromosomes, and Cells

• Cells: fundamental units of life; all organisms are composed of one or more cells

• Genes • Sequences of nucleotides within DNA• Instructions for proteins• Create inheritable traits

• Chromosomes: composed of many genes

Cells, Nuclei, Chromosomes, DNA, and Genes

Fig. 2-7, p. 42

Fig. 2-7, p. 42

A human body contains trillions of cells, each with an identical set of genes.

Each human cell (except for red blood cells) contains a nucleus.

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.

Stepped Art

A human body contains trillionsof cells, each with an identical setof genes.

Each human cell (except for redblood cells) contains a nucleus.

Each cell nucleus has an identical setof chromosomes, which are found inpairs.

A specific pair of chromosomescontains one chromosome from eachparent.

Each chromosome contains a longDNA molecule in the form of a coileddouble helix.

Genes are segments of DNA onchromosomes that contain instructionsto make proteins—the building blocksof life.

Fig. 2-7, p. 42

Some Forms of Matter Are More Useful than Others

• High-quality matter• Highly concentrated• Near earth’s surface• High potential as a resource

• Low-quality matter• Not highly concentrated• Deep underground or widely dispersed• Low potential as a resource

Examples of Differences in Matter Quality

Fig. 2-8, p. 42

Fig. 2-8, p. 42

High Quality Low Quality

Solid Gas

Salt Solution of salt in water

Coal Coal-fired power plant emissions

Gasoline Automobile emissions

Aluminum can Aluminum ore

2-3 What Happens When Matter Undergoes Change?

• Concept 2-3 Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).

Matter Undergoes Physical, Chemical, and Nuclear Changes

• Physical change• No change in chemical composition

• Chemical change, chemical reaction• Change in chemical composition• Reactants and products

• Nuclear change• Natural radioactive decay

• Radioisotopes: unstable• Nuclear fission• Nuclear fusion

Types of Nuclear Changes

Fig. 2-9, p. 43

Fig. 2-9a, p. 43

Radioactive decay occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram.

Radioactive isotope

Radioactive decay

Gamma rays

Alpha particle (helium-4 nucleus)

Beta particle (electron)

Fig. 2-9b, p. 43

Nuclear fissionUranium-235

Uranium-235

Neutron Energy

Fissionfragment

n

nn

nn n

Energy

Energy

Energy

Fissionfragment

Radioactive isotope Radioactive decay occurs when nuclei of unstable isotopesspontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of the three items shown in the diagram.

Neutron

Uranium-235

Fissionfragment

Fissionfragment

Energyn

n

n

Energy

Energy

n

n

n

Energy

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Uranium-235

Stepped ArtFig. 2-9b, p. 43

Fig. 2-9c, p. 43

Nuclear fusion occurs when two isotopes of light elements, suchas hydrogen, are forced together at extremely high temperaturesuntil they fuse to form a heavier nucleus and release a tremendousamount of energy.

Hydrogen-3(tritium nucleus)

100million °C

Reactionconditions

Neutron

Energy

ProductsNeutron

Nuclear fusion

Fuel

Hydrogen-2(deuterium nucleus)

Helium-4 nucleusProton

We Cannot Create or Destroy Matter

• Law of conservation of matter

• Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed

2-4 What is Energy and What Happens When It Undergoes Change?

• Concept 2-4A When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics).

• Concept 2-4B Whenever energy is changed from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with (second law of thermodynamics).

Energy Comes in Many Forms (1)

• Kinetic energy • Flowing water• Wind • Heat• Transferred by radiation, conduction, or convection

• Electromagnetic radiation

• Potential energy • Stored energy • Can be changed into kinetic energy

Wind’s Kinetic Energy Moves This Turbine

Fig. 2-10, p. 44

The Electromagnetic Spectrum

Fig. 2-11, p. 45

Fig. 2-11, p. 45

Visible light

Gamma rays X rays

Shorter wavelengths and higher energy

Longer wavelengths and lower energy

UV radiation

Infrared radiation Microwaves TV, Radio waves

Wavelengths (not to scale)

0.001 0.01 0.1 1 10 0.1 10 100 0.1 1 10 1 10 100

Nanometers Micrometers Centimeters Meters

Potential Energy

Fig. 2-12, p. 45

Energy Comes in Many Forms (2)

• Sun provides 99% of earth’s energy• Warms earth to comfortable temperature• Plant photosynthesis• Winds • Hydropower• Biomass • Fossil fuels: oil, coal, natural gas

Nuclear Energy to Electromagnetic Radiation

Fig. 2-13, p. 46

Fossil fuels

Fig. 2-14a, p. 46

Some Types of Energy Are More Useful Than Others

• High-quality energy• High capacity to do work• Concentrated• High-temperature heat• Strong winds• Fossil fuels

• Low-quality energy• Low capacity to do work • Dispersed

Ocean Heat Is Low-Quality Energy

Fig. 2-15, p. 47

Energy Changes Are Governed by Two Scientific Laws

• First Law of Thermodynamics• Law of conservation of energy• Energy is neither created nor destroyed in

physical and chemical changes• Second Law of Thermodynamics• Energy always goes from a more useful to a less

useful form when it changes from one form to another

• Light bulbs and combustion engines are very inefficient: produce wasted heat

Energy-Wasting Technologies

Fig. 2-16a, p. 48

2-5 What Are Systems and How Do They Respond to Change?

• Concept 2-5 Systems have inputs, flows, and outputs of matter and energy, and feedback can affect their behavior.

Systems Have Inputs, Flows, and Outputs

• System• Set of components that interact in a regular way• Human body, earth, the economy

• Inputs from the environment

• Flows, throughputs of matter and energy

• Outputs to the environment

Inputs, Throughput, and Outputs of an Economic System

Fig. 2-17, p. 48

Fig. 2-17, p. 48

Inputs (from environment) Throughputs

Outputs (to environment)

Energy resources

Work or products

Matter resources

System processes

Waste and pollution

Information Heat

Systems Respond to Change through Feedback Loops

• Positive feedback loop• Causes system to change further in the same

direction• Can cause major environmental problems

• Negative, or corrective, feedback loop• Causes system to change in opposite direction

Positive Feedback Loop

Fig. 2-18, p. 49

Fig. 2-18, p. 49

Decreasing vegetation...

... which causes more vegetation to die.

... leads to erosion and nutrient loss...

Negative Feedback Loop

Fig. 2-19, p. 50

Fig. 2-19, p. 50

House warms

Temperature reaches desired setting and

furnace goes off

Furnace on Furnace off

House cools

Temperature drops below desired setting and furnace goes on

Time Delays Can Allow a System to Reach a Tipping Point

• Time delays vary• Between the input of a feedback stimulus and the

response to it

• Tipping point, threshold level• Causes a shift in the behavior of a system• Melting of polar ice• Population growth

System Effects Can Be Amplified through Synergy

• Synergistic interaction, synergy • Two or more processes combine in such a way

that combined effect is greater than the two separate effects

• Helpful• Studying with a partner

• Harmful• E.g., Smoking and inhaling asbestos particles

The Usefulness of Models for Studying Systems

1. Identify major components of systems and interactions within system, and then write equations

2. Use computer to describe behavior, based on the equations

3. Compare projected behavior with known behavior

• Can use a good model to answer “if-then“ questions

Three Big Ideas

1. There is no away.

2. You cannot get something for nothing.

3. You cannot break even.

chapter 2

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