CHAPTER 2 Science, Matter, Energy, and Systems

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

2. Core Case Study: A Story About a Forest • Hubbard Brook Experimental Forest in New Hampshire • Compared the loss of water and nutrients from an uncut forest (control site) with one that had been stripped (experimental site) • Stripped site: • 30-40% more runoff • More dissolved nutrients • More soil erosion

3. The Effects of Deforestation on the Loss of Water and Soil Nutrients Fig. 2-1, p. 31

4. 2-1 What Do Scientists Do? • Concept 2-1 Scientists collect data and develop theories, models, and laws about how nature works.

5. Science Is a Search for Order in Nature (1) • Identify a problem • Find out what is known about the problem • Ask a question to be investigated • Gather data through experiments • Propose a scientific hypothesis

6. Science Is a Search for Order in Nature (2) • Make testable predictions • Keep testing and making observations • Accept or reject the hypothesis • Scientific theory: well-tested and widely accepted hypothesis

7. The Scientific Process Fig. 2-2, p. 33

8. 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 Scientific law Well-accepted pattern in data Analyze data (check for patterns) Propose a hypothesis to explain data Use hypothesis to make testable projections Perform an experiment to test projections Make testable projections Accept hypothesis Revise hypothesis Test projections Scientific theory Well-tested and widely accepted hypothesis Fig. 2-2, p. 33

9. Testing a Hypothesis Fig. 2-3, p. 33

10. 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. Experiment: Put in a new bulb. Result: Flashlight works. Conclusion: New hypothesis is verified. Fig. 2-3, p. 33

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

12. Science Focus: Easter Island: Revisions to a Popular Environmental Story • Some revisions to a popular environmental story • Polynesians arrived about 800 years ago • Population may have reached 3000 • Used trees in an unsustainable manner, but rats may have multiplied and eaten the seeds of the trees

13. Stone Statues on Easter Island Fig. 2-A, p. 35

14. 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

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

16. 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

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

18. 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.

19. Matter Consists of Elements and Compounds • Matter • 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

20. Gold and Mercury Are Chemical Elements Fig. 2-4a, p. 38

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

22. Atoms, Ions, and Molecules Are the Building Blocks of Matter (1) • Atomic theory • All elements are made of atoms • Subatomic particles • Protons with positive charge and neutrons with no charge in nucleus • Negatively charged electrons orbit the nucleus • Atomic number • Number of protons in nucleus • Mass number • Number of protons plus neutrons in nucleus

23. Model of a Carbon-12 Atom Fig. 2-5, p. 39

24. 6 protons 6 neutrons 6 electrons Fig. 2-5, p. 39

25. Atoms, Ions, and Molecules Are the Building Blocks of Matter (2) • Isotopes • Same element, different number of protons • Ions • Gain or lose electrons • Form ionic compounds • pH • Measure of acidity • H+ and OH-

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

27. pH Scale Supplement 5, Figure 4

28. Loss of NO3−from a Deforested Watershed Fig. 2-6, p. 40

29. 60 Nitrate (NO3–) concentration (milligrams per liter) 40 Disturbed (experimental) watershed Undisturbed (control) watershed 20 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 Year Fig. 2-6, p. 40

30. Atoms, Ions, and Molecules Are the Building Blocks of Matter (3) • Molecule • Two or more atoms of the same or different elements held together by chemical bonds • Compounds • Chemical formula

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

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

33. Glucose Structure Supplement 4, Fig. 4

34. Amino Acids and Proteins Supplement 4, Fig. 8

35. Nucleotide Structure in DNA and RNA Supplement 4, Fig. 9

36. DNA Double Helix Structure and Bonding Supplement 4, Fig. 10

37. Fatty Acid Structure and Trigyceride Supplement 4, Fig. 11

38. Matter Comes to Life through Genes, Chromosomes, and Cells • Cells: fundamental units of life; all organisms are composed of one or more cells • Genes • Sequences of nucleotides within DNA • Instructions for proteins • Create inheritable traits • Chromosomes: composed of many genes

39. Cells, Nuclei, Chromosomes, DNA, and Genes Fig. 2-7, p. 42

40. A human body contains trillions of cells, each with an identical set of genes. Each human cell (except for red blood cells) contains a nucleus. Each cell nucleus has an identical set of chromosomes, which are found in pairs. A specific pair of chromosomes contains one chromosome from each parent. Each chromosome contains a long DNA molecule in the form of a coiled double helix. Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life. Fig. 2-7, p. 42

41. 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

42. Examples of Differences in Matter Quality Fig. 2-8, p. 42

43. High Quality Low Quality Solid Gas Solution of salt in water Salt Coal Coal-fired power plant emissions Gasoline Automobile emissions Aluminum can Aluminum ore Fig. 2-8, p. 42

44. 2-3 What Happens When Matter Undergoes Change? • Concept 2-3 Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).

45. 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

46. Types of Nuclear Changes Fig. 2-9, p. 43

47. Radioactive decay Alpha particle (helium-4 nucleus) Radioactive isotope Gamma rays Beta particle (electron) 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. 2-9a, p. 43

48. Nuclear fission Uranium-235 Energy Fission fragment n n Neutron n n Energy Energy n n Uranium-235 Fission fragment Energy Radioactive isotope 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. 2-9b, p. 43

49. Nuclear fusion Reaction conditions Fuel Products Proton Neutron Helium-4 nucleus Hydrogen-2 (deuterium nucleus) 100 million °C Energy Hydrogen-3 (tritium nucleus) 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. Fig. 2-9c, p. 43

50. We Cannot Create or Destroy Matter • Law of conservation of matter • Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed