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

Undisturbed (control) watershed Disturbed (experimental) watershed Year Nitrate (NO 3 – ) concentration (milligrams per liter)

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

Scientific law Well-accepted pattern in data 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)

Fig. 2-2, p. 25 Make testable predictions Propose an hypothesis to explain data Use hypothesis to make testable predictions Perform an experiment to test predictions Accept hypothesis Scientific theory Well-tested and widely accepted hypothesis Revise hypothesis Test predictions

Scientific theory Well-tested and widely accepted hypothesis Fig. 2-2, p. 25 Stepped Art Test predictions Make testable predictions Accept hypothesis Revise hypothesis Perform an experiment to test predictions Use hypothesis to make testable predictions Propose an hypothesis to explain data Analyze data (check for patterns) Scientific law Well-accepted pattern in data Perform an experiment to answer the question and collect data Ask a question to be investigated Find out what is known about 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

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. 30 Aluminum ore Low QualityHigh Quality Solid Salt Coal Gasoline Aluminum can Gas Solution of salt in water Coal-fired power plant 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 + O 2 Black solid Colorless gas Energy Carbon dioxide + CO 2 + +

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

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

Nuclear fission Uranium-235 Neutron Fission fragment Fission fragment 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 Fission fragment Fission fragment Energy n n n n n n Uranium-235 Fig. 2-5b, p. 32 Stepped Art

Fig. 2-5c, p. 32

Nuclear fusion Fuel ProtonNeutron Hydrogen-2 (deuterium nucleus) Hydrogen-3 (tritium nucleus) 100 million °C Reaction conditions Products Helium-4 nucleus Energy Neutron Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until 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 Solar energy Chemical energy (photo- synthesis) Mechanical energy (moving, thinking, living) Chemical energy (food) Waste heat Waste heat Waste heat Waste heat

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-quality energy (heat) High-quality matter High-quality energy Inputs (from environment) System throughputs High-waste economy Outputs (into environment) Waste and pollution

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 and pollution prevention Low-quality energy (heat) Outputs (into environment) System throughputs Waste and pollution Pollution control Low-waste economy Inputs (from environment) Energy conservation High-quality matter Recycle and reuse

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