AP ENVIRONMENTAL SCIENCE CHAPTER 2:

1. AP ENVIRONMENTAL SCIENCECHAPTER 2: SCIENCE, SYSTEMS, MATTER, AND ENERGY

2. THE NATURE OF SCIENCE • What do scientists do? • Make observations and ask questions • Collect data (experimentation) and interpret or explain data • Take measurements • Make more observations • Form hypotheses, make predictions • Test Predictions • Accept or Reject hypothesis • Develop theories, models, and laws

3. Scientific Hypotheses, Theories and Laws • Scientific Hypothesis: • Plausible explanations based on prior knowledge and a small amount of evidence. An educated guess or prediction. Tested repeatedly to be either proven valid, or invalidated through research. • Scientific Theory: • A widely tested and accepted scientific hypothesis that is supported by enough evidence for scientist to accept it as probable; little or no evidence exists to the contrary. • Scientific Law: • A scientific theory becomes a law when it is observed happening over and over again in nature in the same way each time.

4. Testing Scientific Hypotheses • Scientists test hypotheses by using controlled experiments and by running mathematical models on high-speed computers • VARIABLES: • Controlled Variables: remains constant and unchanged; Provides an example of the norm for comparison purposes. • Independent Variables: changed in a planned and known way • Dependent Variables: changes or is impacted as a result of the change in the independent variable.

5. Testing Scientific Hypotheses • Single Variable Analysis: • Uses two groups: a control group and an experimental group • Multivariable Analysis: • Have a HUGE number of interacting variables. • Overcome by using computer-based mathematical models and simulation programs to analyze interactions of many variables at once, without the need traditional experimentation. • Weather analysis is often done this way. Computer models are not 100% accurate, but traditional, controlled experiments are sometimes flawed by human error also.

6. Scientific Reasoning and Creativity • Inductive Reasoning: • Converts specific observations and measurements to a general conclusion. (“bottom-up” reasoning) • Example: • Observation: A variety of different objects fall to the ground when dropped from a specific height. • Conclusion: All objects fall to the earth’s suface when dropped. • Deductive Reasoning: • Logically converts a generalization to a specific conclusion. (“top-down” reasoning) • Example: • Generalization/premise: All birds have feathers • Example: Eagles are birds • Deductive Conclusion: All eagles have feathers.

7. Scientific Reasoning and Creativity • Syllogism: • A series of logically connected statements • Only valid if faulty logic is not used to arrive at the conclusion • Deductive and Inductive reasoning and critical thinking skills are important, required scientific tools. • Intuition, imagination and creativity are also important skills scientists need and use to explain some observations in nature. • Often imaginative ideas defy conventional logic and current scientific knowledge and understanding.

8. Major Changes in Scientific Theories • Paradigm Shift: • When new ideas or information disprove a well-accepted scientific theory. • Occurs when the majority of scientists in a field or related fields agree that a new explanation or theory is better than the old one. • Scientific theories have a high probability of being valid, but are not infallible. • Example: Ptolemy proposed that the Earth was the center of the universe. Became an accepted theory that lasted 1,400 years. • Disproven in 1543 by Copernicus who provided new evidence that the sun is the center of our solar system. This “new” view has been an accepted theory for more than 460 years.

9. Frontier Science and Sound Science • Frontier Science: When experiments result in new data that has not yet been confirmed. (Work in progress). • Preliminary results • Often controversial • Some will later be discredited, some will be validated • Sound Science: Experimental results that have been repeatedly tested and widely accepted as valid results. • Consists of data, theories and laws that are widely accepted. • Subjected to peer review • Results are reproducible

10. Junk Science • Junk Science: • Scientific results that have been obtained unscientifically and are presented as sound science without having undergone the rigors of peer review, or that have been discarded as a result of peer review.

11. How to Detect Junk Science: 1. What data support the hypotheses? • Verifieddata? • Reproducibledata? 2. Do the conclusions follow logically from the data? 3. Does the explanation account for all observations? • No alternative explanations? 4. Are the investigators unbiased in their interpretations of the data? a. Is data free from Hidden agendas? b. Is funding from an unbiased source? 5. Conclusions verified by impartial peer review? 6. Conclusions widely accepted by the scientific community or experts in the field?

12. Junk Science, (continued): • If all answers to the previous questions are “YES”, then the results can be classified as “sound” science. • If all answers are NOT “yes”, it is either Frontier or Junk science and further investigation is warranted before claims can be made based on the data. • Reporters sometimes report a mixture of sound science with junk science, or use a quote from a non-expert. • This can cause the general public to mistrust sound science or to believe junk science that is not widely accepted by expert scientists.

13. Limitations of Environmental Science • Scientists can disprove ideas but cannot prove anything absolutely. • Uncertainty always present in scientific measurements, observations, and models. • Scientists examine concepts in terms of probability rather than absolutes: • Example: A scientist would not say “Cigarettes cause lung cancer.” Instead, a scientist would say something like: “Overwhelming evidence from thousands of studies indicates that there is a significant link or relationship between cigarette smoking and lung cancer.”

14. Limitations of Environmental Science (continued) • Humans cannot be expected to be totally free of bias, but bias can be minimized. • Validity of data and built-in error: • No accurate way to measure how many metric tons of soil are eroded worldwide each year, for example. • Statistical sampling methods used instead to estimate such numbers, creating built in “error” in the results. • These can still indicate important trends • Multiple variables and complex interactions make environmental problems difficult to completely understand. • Earth systems • Current state of environmental health • Environmental impact of human activities

15. What is a System? • Scientists predict the behavior of a complex system by developing a model of the inputs, throughputs (flows), and outputs of matter, energy, and information. • System: a set of components that function and interact in some regular and theoretically understandable manner. • Examples of systems: • Human body • Population of tigers • A river • An economy • The entire earth

16. Components of a System • Inputs: Factors coming in from the environment • Flows or throughputs: factors flowing through the system at a certain rate • Outputs: Factors leaving the system and returning to the environment. • Scientist use models to approximate or visualize how the components of a system work together and to evaluate hypotheses.

17. Models and Behavior of Systems • Mathematical models • Constructed in steps • Step 1: make a guess and write equations • Step 2: compute likely behavior of system, implied by equations • Step 3: compare projected behavior with observations and behavior projected by mental models, existing data, hypotheses, theories, or laws. • Particulary useful when there are many interacting variables present in the system, when time frame is long, or when controlled experiments are impossible, too slow, or too expensive. • Used to predict what is likely to happen under a variety of conditions. • No better than the assumptions on which they are built and the data fed into them

18. How Systems Respond to Change • Feedback Loops • Outputs of matter, energy, or information fed back into a system • can cause the system to do more of what it was doing (postive feedback) or less of what it was doing (negative feedback) • Positive Feedback Loop • Bring levels out of normal range by elevating or reducing levels. • Example: Depositing money in a bank at compound interest and leaving it there. Interest increases the balance which through a positive feedback loop leads to more interest and an even higher balance. • Negative Feedback Loop • Bring levels back into normal range by elevating or reducing levels. • Example: recycling aluminum cans feeds recycled aluminum back into the economic system, reducing the need to find, extract and process virgin aluminum ore.

19. Synergy: Amplifying Responses • Processes and Feedbacks in a system can sometimes interact to amplify the results. • SYNERGISTIC INTERACTION (SYNERGY): • Occurs when two or more processes interact so that the combined effect is greater than the sum of their separate effects. • Example: • Lifetime cigarette smokers = 10X the normal chance of developing lung cancer • People exposed to asbestos for long periods = 5X the normal chance of developing lung cancer • People who smoke AND are exposed to asbestos = 50X the normal chance of developing lung cancer • Synergy is why working together can many times help us solve problems more effectively and efficiently than working alone.

20. Unintended Human Harm • Human activities in a complex system often lead to unintended harmful results and environmental surprises. • “WE CAN NEVER DO JUST ONE THING” to a system • One of the four guidelines for living sustainably (see principles of sustainability) • Any human action in a complex system has multiple, unintended and often unpredictable effects. • Even by simply observing a system, we affect it. • Most of the environmental problems we face today are unintended results of activities designed to increase the quality of human life. • Example: Many people believe the Affordable Healthcare Act may eventually have the unintended affect of destroying the private health insurance industry, resulting in a single-payer form of socialized medicine.

21. Discontinuity • DISCONTINUITY • Abrupt change in a previously stable system when some unforeseen environmental threshold is crossed. • Example: You can lean back in a chair and balance yourself on two of its legs for a long time with only minor adjustments, but when you pass a certain threshold, your balance system suffers a discontinuity (sudden shift), and you may find yourself on the floor. • According to scientific evidence, we are crossing an increasing number of environmental thresholds, which will inevitably cause a collapse of many environmental and economical systems. • Example 1: When we exceed the sustainable yield of a fishery for a number of years, the available fish decline to the point where it is not profitable to harvest them. • Example 2: Many trees may start dying after being weakened because of depleted soil nutrients and constant exposure to air pollutants. • Other Examples: Dying coral reefs, melting glaciers, rising seas

22. Changes in Matter • Physical changes: No change in chemical composition • Examples: • Cutting aluminum foil into smaller pieces • Change in the state of the matter (melting, freezing, etc) • Chemical changes: causes a change in chemical composition • Examples: • Coal burning (energy is released)

23. Law of Conservation of Matter • States that when a physical or chemical change occurs, no atoms are created or destroyed. • Means there is no such thing as “away” in the phrase “to throw away” • Everything we think we have destroyed, remains here with us in some form. • We can remove pollutants from water, (but then we must burn them, producing air pollution instead), bury them, (contaminating soil and ground water), or clean them up and apply the gooey sludge to the land as fertilizer, (dangerous if the sludge contains nondegradable toxic metals such as lead and mercury).

24. Types of Pollutants • Three factors how harmful the effects: • Chemical nature • How reactive are the atoms/molecules comprising the chemical • Concentration • Usually described in terms of ppm (parts per million), ppb (parts per billion), or ppt (parts per trillion) • Example: ppm = 1 part pollutant, 1 million parts gas, liquid or solid mixture in which the pollutant is found. • Persistence in the environment • How long the pollutant stays in the air, water, soil, or body. • Pollutants are categorized based on their persistance: • Degradable: broken down completely by natural processes • Biodegradable: broken down completely by living organisms • Slowly degradable: take decades or longer to degrade • Nondegradable: chemicals that natural processes can’t degrade

25. Nuclear Changes: Fusion and Fission • The nuclei of some atoms can… • Lose particles or give off radiation, • Split apart, • Or fuse together • Natural Radioactive decay: • A change in the nucleus in which unstable isotopes, (called radioisotopes), suddenly emit fast moving chunks of matter (alpha or beta particles), high energy radiation, (gamma rays), or both, at a fixed rate, unique, (and thus predictable) rate for each type of radioisotope. • This “predictable rate of decay” is expressed by the term “half-life.”

26. Half Life • Half Life: the time needed for one-half of the nuclei in a given quantity of a radioisotope to decay and emit their radiation to form a different isotope. • This decay continues until a nonradioactive isotope is formed. • Half-lives range from millionths of a second to several billion years. • A substance’s half life can’t be changed by any factor known to man. • Used to estimate how long radioisotopes must be quarantined before they reach safe levels of radioactivity. • Rule of thumb: 10 half lives • Example: Iodine-131 half life = 8 days, so people need to be protected from it for 80 days

27. Fission and Fusion • Nuclear Fission: The splitting of atomic nuclei • Releases energy and more neutrons that can trigger additional fission reactions. This chain reaction creates an enormous amount of energy. • Nuclear Fusion: The forcing together of two atoms, causing them to form a heavier nucleus. • Requires extremely high temperatures • Releases a tremendous amount of energy • Sun’s source of energy • Uncontrolled nuclear fusion used to develop nuclear bombs

28. ENERGY • Work needed to move matter and the heat that flows from hot to cooler samples of matter. • The ability to do work • Different forms of energy: • Electrical • Mechanical • Light (electromagnetic) • Heat • Chemical

29. ENERGY • There has been a dramatic increase in energy use over time • Primitive man = 2000 kilocalories per day • Modern man = 2000 kilocalories PLUS about 600,000 kilocalories for industry per day. • Today – Fossil Fuel era persists:; 82% of energy from non-renewable resources; Gap in energy use, with developed countries using 300 times more than developing nations.

30. Kinetic and Potential Energy • Kinetic: Moving • Wind, streams, electricity, • Heat = total kinetic energy of all moving atoms, ions, ,or molecules in a substance • Electromagnetic radiation = energy travels in the form of a wave due to changes in electric and magnetic fields. • Different forms of electromagnetic energy with different wavelengths • Potential: stored (at rest), potentially available for use • Can be converted into kinetic energy • Examples: • Rock held in hand • Unlit match • Still water behind a dam • Chemical energy stored in gasoline • Nuclear energy stored in the nuclei of atoms • Energy stored in an ATP molecule • Batteries, (not in use)

31. Energy Quality • High Quality • Concentrated • Can be used to perform much work • Examples: • Electricity • Chemical energy of coal and gasoline • Concentrated sunlight • Nuclear energy • Low Quality • Dispersed, diluted • Little ability to do work • Examples: • Heat dispersed in the atmosphere or ocean

32. Energy Laws • First Law of Thermodynamics • One can not create or destroy energy • Energy just gets converted to another form; NRG input = NRG output • Can’t get something from nothing • AKA: Law of conservation of energy

33. Energy Laws • Second Law of Thermodynamics • When energy changes form, high quality, useful energy is always degraded to lower-quality, less useful energy • Usually dissipates in the form of heat. • Example: 10% of the energy in your food is available for use; 90% is given off as heat • Example: 6% of the energy in gasoline powers your car, 94% is degraded to low quality heat • (Therefore 94% of the money you spend on gas is not used to transport you anywhere).

34. Energy Efficiency • Energy Efficiency – the measure of how much useful work is accomplished by a particular input of energy into a system. • Only 16% of the energy used in the United States ends up performing useful work. • 84% is unavoidably wasted because of 2nd Law of Thermodynamics, or unnecessarily wasted. • The quickest and cheapest way to come by more energy is to stop wasting almost half of the energy we use.

35. Sustainability Regarding The Laws of Matter and Energy • Unsustainable High-Throughput Economies: • Working in Straight Lines • Convert world’s resources to goods and services in ways that add waste, pollution, and low quality heat to the environment. • Matter-Recycling-and-Reuse Economies: • Recycling and reusing matter resources • Slows down depletion of nonrenewable resources • Reduces Environmental Impact • Sustainable Low-Throughput Economies • Reduces the throughput of all matter and energy in our economies • Less waste of matter and energy • Stabilizes population sizes.