Science, Matter, and Energy

Chapter 2

Core Case Study: Controlled Scientific Experiment (1)

Hubbard Brook Experimental Forest

Question: What is the environmental impact of forest clear-cutting?

Controlled experiment – isolate variables • Control site• Experimental site

Core Case Study : Controlled Scientific Experiment (2)

Measure loss of water and nutrients

Compare results• 30–40% increase in runoff• 6–8 times more nutrient loss

Draw conclusions• Cause-and-effect relationships

Controlled Experiment Measures Effects of Deforestation

Fig. 2-1, p. 23

Loss of Nitrate Ions

Fig. 2-3, p. 29

Fig. 2-3, p. 29

Undisturbed(control)watershed

Disturbed(experimental)watershed

Year

Nit

rate

(N

O3

– )

co

nc

entr

ati

on

(mill

igra

ms

pe

r lit

er)

2-1 What Is Science?

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

Science

Search for order in nature• Observe behavior• Attempt to quantify cause and effect• Make predictions

The Scientific Process (1)

Identify problem/question

Design experiments

Collect data

Formulate hypothesis

The Scientific Process (2)

Develop models

Propose theories

Derive natural laws

What Scientists Do

Fig. 2-2, p. 25

Fig. 2-2, p. 25

Scientific lawWell-acceptedpattern in data

Identify a problem

Find out what is knownabout the problem(literature search)

Ask a question to beinvestigated

Perform an experimentto answer the question

and collect data

Analyze data(check for patterns)

Fig. 2-2, p. 25

Make testablepredictions

Propose an hypothesis

to explain data

Use hypothesis to make testable

predictions

Perform an experiment

to test predictions

Accepthypothesis

Scientific theoryWell-tested andwidely accepted

hypothesis

Revisehypothesis

Testpredictions

Scientific theoryWell-tested andwidely accepted

hypothesis Fig. 2-2, p. 25

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

Results of Science

Goals• Scientific theories• Scientific laws

Degree of certainty and general acceptance• Frontier science• Reliable science• Unreliable science

Scientific Limitations

Limitations – 100% certain?• Absolute proof versus probability• Observational bias• Complex interactions, many variables• Estimates and extrapolating numbers

Science does not answer moral or ethical questions

Science Focus: Easter Island

Solving a mystery• Population crash – cause and effect

Evolving hypotheses• Unsustainable resource use?• Rats?• Disease?• Slave trade?

Science as a process

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.

What Is Matter?

Matter – has mass and occupies space

Elements and Compounds• Atoms• Ions• Molecules

Elements Important to the Study of Environmental Science

Building Blocks of Matter (1)

Atomic Theory – elements made from atoms

Atoms• Protons – positive charge• Neutrons – uncharged• Electrons – negative charge

Building Blocks of Matter (2)

Atomic number• Number of protons

Mass number• Neutrons + protons

Isotopes• Same atomic number, different mass

Building Blocks of Matter (3)

Ions• One or more net positive or negative electrical

charges

Chemical formula• Number and type of each atom or ion

Compounds• Organic• Inorganic

Ions and Compounds Important to the Study of Environmental Science

Ions and Compounds Important to the Study of Environmental Science

Organic Compounds

Carbon-based compounds

Examples• Hydrocarbons• Chlorinated hydrocarbons• Simple carbohydrates• Complex carbohydrates• Proteins• Nucleic acids (DNA and RNA)

Matter Quality

Usefulness as a resource • Availability• Concentration

High quality

Low quality

Examples of Matter Quality

Fig. 2-4, p. 30Aluminum ore

Low QualityHigh Quality

Solid

Salt

Coal

Gasoline

Aluminum can

Gas

Solution of salt in water

Coal-fired powerplant emissions

Automobile emissions

2-3 How Can Matter Change?

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

Changes in Matter

Physical

Chemical

p. 31

Reactant(s) Product(s)

Carbon + Oxygen

C + O2

Black solid Colorless gasColorless gas

Energy

Energy

Energy

Carbon dioxide +

CO2 +

+

Nuclear Changes (1)

Radioactive decay – unstable isotopes• Alpha particles• Beta particles• Gamma rays

Nuclear Changes (2)

Nuclear fission • Large mass isotopes split apart• Chain reaction

Nuclear fusion• Two light isotopes forced together• High temperature to start reaction• Stars

Types of Nuclear Changes

Fig. 2-5a, p. 32

Fig. 2-5a, p. 32

Radioactive decay

Radioactive isotope

Gamma rays

Beta particle (electron)

Alpha particle(helium-4 nucleus)

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.

Fig. 2-5b, p. 32

Fig. 2-5b, p. 32

Nuclear fission Uranium-235

Uranium-235

Neutron

Fissionfragment

Fissionfragment

Energy

Energy

Energy

Energy

Nuclear fission occurs when the nuclei of certain isotopes with large mass numbers (such as uranium-235) are split apart into lighter nuclei when struck by a neutron and release energy plus two or three more neutrons. Each neutron can trigger an additional fission reaction and lead to a chain reaction, which releases an enormous amount of energy.

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 Fig. 2-5b, p. 32

Stepped Art

Fig. 2-5c, p. 32

Fig. 2-5c, p. 32

Nuclear fusion

Fuel

Proton Neutron

Hydrogen-2(deuterium nucleus)

Hydrogen-3(tritium nucleus)

100million °C

Reactionconditions Products

Helium-4 nucleus

Energy

Neutron

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 tremendous amount of energy.

Law of Conservation of Matter

Matter only changes from one form to another

There is no “throwing away”

Environmental implications• Recycle• Reuse• Must deal with wastes and pollutants

2-4 What Is Energy and How Can It Change Its Form?

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, we end up with lower quality or less usable energy than we started with (second law of thermodynamics).

What Is Energy?

Energy – the capacity to do work or transfer heat

Types of Energy

Potential energy – stored energy• Gasoline• Water behind a dam

Kinetic energy – energy in motion• Wind, flowing water, electricity• Heat – flow from warm to cold• Electromagnetic radiation • wavelength and relative energy

Electromagnetic Radiation

Energy Quality

High-quality energy – concentrated• High temperature heat• Nuclear fission• Concentrated sunlight• High-velocity wind• Fossil fuels

Low-quality energy – dispersed• Heat in atmosphere and ocean

Laws of Conservation of Energy (Thermodynamics)

First law of thermodynamics • Energy input = Energy output

Second law of thermodynamics • Energy use results in lower-quality energy• Dispersed heat loss

Consequences of the Second Law of Thermodynamics (1)

Automobiles• ~6% moves car• ~94% dissipates as low-quality heat into the

environment

Incandescent light bulb• ~5% useful light• ~95% heat

Consequences of the Second Law of Thermodynamics (2)

Living systems• Energy lost with every conversion

Second Law of Thermodynamics and Its Effect on Living Systems

Fig. 2-7, p. 34

Solarenergy

Chemical energy(photo-

synthesis)

Mechanicalenergy

(moving,thinking, living)

Chemicalenergy(food)

Wasteheat

Wasteheat

Wasteheat

Wasteheat

2-5 How Can We Use Matter and Energy More Sustainably?

Concept 2-5A The processes of life must conform to the law of conservation of matter and the two laws of thermodynamics.

Concept 2-5B We can live more sustainably by using and wasting less matter and energy, recycling and reusing most matter resources, and controlling human population growth.

High-throughput (High-waste) Economy

Increase flow of matter and energy to boost economy

Environmental capacity?

High-throughput Economy

Fig. 2-8, p. 36

Low-qualityenergy (heat)

High-qualitymatter

High-qualityenergy

Inputs(from environment)

Systemthroughputs

High-wasteeconomy

Outputs(into environment)

Waste andpollution

Low-throughput (Low-waste) Economy

Matter recycling and reuse economy

Mimic nature

Maximize matter cycling with minimal energy input

Low-throughput Economy

Fig. 2-9, p. 36

High-quality energy

Waste andpollution

prevention

Low-qualityenergy (heat)

Outputs(into environment)

Systemthroughputs

Waste andpollution

Pollutioncontrol

Low-wasteeconomy

Inputs(from environment)

Energyconservation

High-quality matter

Recycle andreuse

Animation: Subatomic particles

Animation: Atomic number, mass number

Animation: Ionic bonds

Animation: Carbon bonds

Animation: Half-life

Animation: Visible light

Animation: Total energy remains constant

Animation: Energy flow

Animation: Economic types

Animation: Martian doing mechanical work

Animation: Energy flow from Sun to Earth

Animation: Energy Use

Animation: Hubbard Brook Experiment

Animation: Categories of Food Webs