Science, Matter, Energy, and Systems CHAPTER 2 Science, Matter, Energy, and Systems 1

The Effects of Deforestation on the Loss of Water and Soil Nutrients Figure 2.1: This controlled field experiment measured the effects of deforestation on the loss of water and soil nutrients from a forest. V– notched dams were built at the bottoms of two forested valleys so that all water and nutrients flowing from each valley could be collected and measured for volume and mineral content. These measurements were recorded for the forested valley (left), which acted as the control site, and for the other valley, which acted as the experimental site (right). Then all the trees in the experimental valley were cut and, for 3 years, the flows of water and soil nutrients from both valleys were measured and compared. Fig. 2-1, p. 31 2

The Scientific Process Figure 2.2: This diagram illustrates what scientists do. Scientists use this overall process for testing ideas about how the natural world works. However, they do not necessarily follow the order of steps shown here. For example, sometimes a scientist might start by coming up with a hypothesis to answer the initial question and then run experiments to test the hypothesis. Fig. 2-2, p. 33 3

Testing a Hypothesis Figure 2.3: We can use the scientific process to understand and deal with an everyday problem. Fig. 2-3, p. 33 4

Nothing happens when I try to turn on my flashlight. Observation: 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. Figure 2.3: We can use the scientific process to understand and deal with an everyday problem. Experiment: Put in a new bulb. Result: Flashlight works. Conclusion: New hypothesis is verified. Fig. 2-3, p. 33

Characteristics of Science…and Scientists Curiosity Skepticism Reproducibility Peer review Openness to new ideas Critical thinking Creativity 6

Stone Statues on Easter Island Figure 2.A: These and many other massive stone figures once lined the coasts of Easter Island and are the remains of the technology created on the island by an ancient civilization of Polynesians. Some of these statues are taller than an average five-story building and can weigh as much as 89 metric tons (98 tons). Fig. 2-A, p. 35 7

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 8

The Results of Science Can Be Tentative, Reliable, or Unreliable Tentative science, frontier science Reliable science Unreliable science 9

Science Has Some Limitations Particular hypotheses, theories, or laws have a high probability of being true while not being absolute Bias can be minimized by scientists Environmental phenomena involve interacting variables and complex interactions Statistical methods may be used to estimate very large or very small numbers Scientific process is limited to the natural world 10

Science Focus: Statistics and Probability Collect, organize, and interpret numerical data Probability The chance that something will happen or be valid Need large enough sample size 11

Matter Consists of Elements and Compounds 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 12

Chemical Elements Used in The Book Table 2-1, p. 38 13

Chemical Ions Used in This Book TABLE 2-2 Table 2-2, p. 40 14

Nitrate (NO3–) concentration (milligrams per liter) 60 Nitrate (NO3–) concentration (milligrams per liter) 40 Disturbed (experimental) watershed Undisturbed (control) watershed 20 Figure 2.6: This graph shows the loss of nitrate ions (NO3–) from a deforested watershed in the Hubbard Brook Experimental Forest (Figure 2-1, right). The average concentration of nitrate ions in runoff from the experimental deforested watershed was about 60 times greater than in a nearby unlogged watershed used as a control (Figure 2-1, left). (Data from F. H. Bormann and Gene Likens) 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 Year Fig. 2-6, p. 40

Compounds Used in This Book Table 2-3, p. 40 16

Organic Compounds Are the Chemicals of Life Hydrocarbons and chlorinated hydrocarbons Simple carbohydrates Macromolecules: complex organic molecules Complex carbohydrates Proteins Nucleic acids Lipids Inorganic compounds 17

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 18

Solution of salt in water High Quality Low Quality Solid Gas Salt Solution of salt in water Coal Coal-fired power plant emissions Figure 2.8: These examples illustrate the differences in matter quality. High-quality matter (left column) is fairly easy to extract and is highly concentrated; low-quality matter (right column) is not highly concentrated and is more difficult to extract than high-quality matter. Gasoline Automobile emissions Aluminum can Aluminum ore Fig. 2-8, p. 42

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 20

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). 21

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 22

Potential Energy Figure 2.12: The water stored in this reservoir behind a dam in the U.S. state of Tennessee has potential energy, which becomes kinetic energy when the water flows through channels built into the dam where it spins a turbine and produces electricity—another form of kinetic energy. Fig. 2-12, p. 45 23

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 24

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 25

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 26