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

2. 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

3. 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

4. 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

5. 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

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

7. 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

8. 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

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

10. 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

11. 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

12. 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

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

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

15. 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)
Year
Fig. 2-6, p. 40

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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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