Chapter 4

1. Chapter 4 SCIENTIFIC THINKING • REQUIREMENT: • Knowledge gathered and evaluated by testing hypotheses and sharing results.  • THE SCIENTIFIC METHOD: • 1. Observation • Unaided senses or with technical devices. è Why?

2. Chapter 4 • 2. Hypothesis Formation • Statement that possibly explains the “Why”. • As simple as possible, but no more so. • Must be “testable”. è experiments • “controlled”, whenever possible

3. Chapter 4 • 3. Hypothesis Testing • Goal: Support or Disprove the hypothesis. • Does not always occur • May take many experiments to achieve goal.

4. Chapter 4 • 4. Critical Evaluation of Results •  Experiments must be repeatable by others. • 5. è Publish Results • Anonymous review. • Others attempt to repeat. • Enough examination results in a “law”. • Broadly written statements known as “theories”.

5. Chapter 4 Example: • Observation: • Some fish in rivers have tumors. • Hypothesis: • Toxic chemicals released by factory.  • Testing: • Examine fish above and below the factory for tumors.  • Critical Evaluation: • Factory scientists conduct similar tests.

6. Chapter 4 Limitations of Science • “Untestable hypotheses” è politics è family planning è beauty of landscapes  • We still comment (ethical and moral opinions just like everybody else).  Data versus Opinions è Environmental Scientists typically predict the future (opinion).

7. No Data Interpolated Extrapolated Data Time Chapter 4 Time

8. Chapter 4 Structure of Matter • Matter: takes up space and has weight. è kinetic molecular theory • all matter is made up of particles which always are in motion (energy of motion).

9. Chapter 4 • Particles: atoms • è atoms form “elements” • atom + atom = molecule • Compounds • Mixtures

10. Chapter 4 Atomic Structure • nucleus: center region • protons and neutrons • (isotopes - neutrons # different) • electrons: outer regions • ions - electrons lost, positive or negative charge result • è Periodic Table pg 462

11. Chapter 4 Molecular Structure & Chemical Reactions • Chemical Bonds è Interaction of electrons, resulting in physical attraction. è Takes energy to make bonds. è Energy released when bonds broken. • Usually requires “activation energy” • “Catalyst” lowers amount of activation energy required, but is not used up.

12. Chapter 4 • Stopped 28-jan2002 • Organic versus Inorganic Matter: • Organic matter has carbon. • Organic matter typically has large molecules. • Many ways to combine large size molecules: • è large variety of organics.

13. Chapter 4 Organic versus Inorganic Matter (cont’d): • Life is based on organic molecules: manufacture or capture • Lots of energy available when breaking down organic molecules—oil, coal, sugar, fat, etc

14. Chapter 4 • Inorganic Matter • Molecules generally smaller • Fewer kinds • Salt, sand, oxygen, water • Oxygen and water may be necessary for organic life but are not organic on their own • We are only familiar with life which is based on organic matter

15. Chapter 4 Two Primary Chemical Reactions: • Photosynthesis: • CO2 +2H2O + energy è O2 + “CH2O” + H2O • (energy in the form of sunlight) • 3 billion years of photosynthesis • No photosynthesis---no life

16. Chapter 4 Respiration: • “CH2O” + O2è CO2 + H2O + energy (energy in the form of ATP) On a global scale, photosynthesis and respiration are roughly equal.

17. Chapter 4 Acids, Bases and pH • Acids have extra H+ (hydrogen ions).  • èable to attract electrons.  • Bases have extra OH- (hydroxyl ions). è able to donate electrons pH --- A measure of how many H+ ions are in a solution.  pH = 7: # of H+ = # of OH-  Small pH (less than 7) indicates excess H+.  Large pH (greater than 7) indicates excess OH-.

18. Chapter 4 Energy Principles • Matter and energy inseparably linked. • Energy defined as the ability to move matter over a distance.  • State of matter (solid, liquid and gas) is due to the amount of energy in the molecules. è to change “state”, alter energy

19. Chapter 4 2 Important Kinds of Energy: • Kinetic Energy: • energy contained in moving objects. •  Potential energy: energy contained in objects which can fall.

20. Chapter 4 L Laws of Thermodynamics First Law of Thermodynamics:  • Energy cannot be created or destroyed, but merely changed from one form to another. • Second Law of Thermodynamics: • When changing forms of energy, “useful” energy is lost (usually as heat).

21. Chapter 4 Implications:  • Energy released throughout the environment as “things” happen. è entropy • the process of becoming disorganized (giving up energy as heat). • Total energy remains constant (quantity), but the move is from usable to unusable energy (quality). • Heat in the ocean can’t be captured since we can’t make if flow from one object to another • Energy in a river can be captured only if we can concentrate it over a very short distance.

22. Chapter 4 Efficiency of energy conversion:  • NOTHING is 100% efficient in converting energy from one from to another. • Plants convert about 1% of sunlight striking earth to organic energy.  • A cow converts about 10% of plant’s energy into organic energy. • A person converts about 10% of a cows energy into organic energy.

23. Chapter 4 Only a small amount of the universe’s energy is in a usable form. Energy is lost as heat in every reaction. Combustion (burning) is VERY good at converting from usable to unusable energy.