Science

2. Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house.Henri Poincare

3. Science Chapter 2 Science, Matter, Energy, and Systems

4. Key Concepts • Scientists collect data, develop theories, models and laws • Matter is made up of atoms, elements and molecules • Law of conservation of matter • First law of thermodynamics • Second law of thermodynamics • Systems have inputs, outputs and feedback

5. Science: A Search for Order • Effort to discover how nature works • Uses observations, measurements, experiments • Assumes that natural events follow cause-and -effect

6. The Scientific Method • Identify problem • Literature search • Ask question to be investigated • Perform experiment • Analyze data (check for patterns) • Formulate hypothesis to explain data • Perform experiment to test hypothesis • Accept hypothesis/ Reject hypothesis • Scientific Theory Revise hypothesis

7. Elements of the Experiment • Variables: factors that affect processes in the experiment *independent variable- tested variable ** dependent variable- measured variable • Only I variable is tested at a time • Experimental group has independent variable • Control group lacks tested variable (provides basis for comparison)

8. Features of Scientific Processes • Curiosity • Creativity • Critical thinking • Skepticism • Reproducibility • Peer review

9. Goals of Science • Scientific theories: well-tested, widely accepted related hypotheses *may be revised with new info • Scientific laws/law of nature: well-tested, widely accepted descriptions of what is found repeatedly in nature *cannot be broken • Models: simulation of a natural system

10. Results of Science • Tentative/frontier science: results that are not yet reliable (new findings) • Reliable science: accepted by scientific consensus • Unreliable science: rejected by scientific consensus (usually because results were not reproducible)

11. Limits of Science • Scientists cannot prove or disprove anything absolutely • Scientists are not totally free of bias • Natural systems involve too many variables to control (important to environmental science) • Statistical sampling is often used to estimate measurements (think: probability) • Cannot be applied to ethical questions

12. Matter • Anything with mass, volume • Physical states: solid, liquid, gas • Exists as an element (fundamental) or in compounds (combinations of different elements)

13. Atoms/Elements • Basic unit of matter *atomic theory: atoms make up elements • Internal structures: neutrons (n), protons (p), electrons (e) • Atomic number: equals number of protons • Mass number: total number of protons and neutrons • Isotopes: same atomic number, but different mass

14. Helium - electron - N + proton + N neutron Atomic Number: 2 Atomic Mass: 4

15. Isotopes

16. Molecule/Compound • Two or more different element chemical bound *covalent bond: valence electrons are shared ** ionic bond: movement of electrons between ions Covalent bond Ionic bond

17. Ions • Atom/group of atoms with a positive or negative charge (superscript indicates charge- NH₄⁺) • Important for measuring acidity: * determines how materials dissolve ** measured by pH: 0--------------------------7----------------------------14 More H⁺ than OH¯ More OH¯ than H⁺

18. Compounds • Organic: contain at least 2 carbons • Inorganic: all other compounds

19. Organic Compounds • Hydrocarbons: C, H (methane-CH₄) • Chlorinated hydrocarbons: C, H, Cl (DDT) • Simple carbohydrates: C,H,O (glucose) • Macromolecules: complex carbohydrates, porteins, nucleic acids and lipids

20. Macromolecules

21. Macromolecules

22. Macromolecules

23. Macromolecules

24. Living Matter • Cell: basic functioning unit of life (cell theory) • Genes: sequences of nucleotides that code for specific traits • Chromosome: made up of thousands of genes

25. Matter Quality • Measure of how useful matter is to humans; based on availability, concentration * high quality matter: high concentration, great resource, usually found near Earth’s surface ** low quality matter: low concentration, resource, deep underground or dispersed

27. Types of Change in Matter • Physical change: no change in chemical composition (ice melting) • Chemical change/reaction: change in chemical composition

28. Types of Change in Matter (cont’d) • Nuclear change: change in the nuclei of atoms • Radioactive decay: unstable isotope sheds fast-moving particles - half life: time needed for ½ of nuclei to decay into a more stable form • Nuclear fission: nuclei of isotopes with large mass split into lighter nuclei • Nuclear fusion: two isotopes of light elements fuse to form a heavier nucleus

29. Nuclear Changes Radioactive Half-Lives

30. Nuclear Changes Fission Fusion

31. Law of Conservation of Matter • No atoms are created or destroyed when matter undergoes physical or chemical changes (This law means we really cannot “throw” away anything. Pollution changes form, but never goes away)

32. Energy • Capacity to do work or to transfer heat • Kinetic energy: associated... 1. motion 2. heat (moving atoms; flow from cold to hot) 3. electromagnet radiation a. travels in waves b. wavelength reflects energy (shorter waves = greater energy)

33. Energy (cont’d) Electromagnetic Radiation

34. Energy (cont’d) • Potential energy: stored (potential for us)

35. Natural/Commercial Energy Sources • Sun is source for most energy on Earth • Solar energy produces wind, hydropower, biomass fuels • Fossil fuels (oil, coal, natural gas) produces commercial energy

36. Energy Quality • High-quality energy: concentrated, high work capacity ex.s- high temperatures, direct sunlight, burning coal • Low-quality energy: dispersed, low work capacity ex.s- low temperatures, indirect sunlight, burning crop wastes

37. Energy Quality

38. Laws of Energy Transfer • First law of thermodynamics: no energy is created or destroyed when energy is converted from one form to another • Second law of thermodynamics: energy conversions always result in a less useful form of energy due to loss in form of heat (we can never reuse/recycle energy to do work)

39. Systems • Set of components that function and interact in a regular way. Made up of: • Inputsfrom the environment • Flows/throughputs of matter or energy within system • Outputsto the environment ex.s- human body, an economy, a river

40. Systems

41. System Changes • Feedback: process that increases (positive) or decreases (negative) a change to a system • Feedback loop: output is fed backinto a system as input; results in change to the system

42. Positive Feedback Loop • Causes system to increase change in same direction Ex:

43. Negative Feedback Loop • Causes a system to move in the opposite direction from which it is moving ex:

44. System Regulations • Time delay: time between the input of a feed- back stimulus and the system’s response to it ex. Replanting a forest to slow erosion • Tipping point: point at which a system is changed irreversibly ex. Erosion results in so much nutrient loss that land can no longer support trees

46. Synergy • Synergistic interaction (synergy): interaction of two or more processes to create a greater effect than each process separately (ex. Nonsmoker exposed to asbestos is 5 х more likely to get cancer than a smoker; a smoker exposed to asbestos is 50 х more likely to get cancer than a nonsmoker)