Chapter 2 – Science, Matter, Energy and Systems

1. Chapter 2 – Science, Matter, Energy and Systems Endeavor to discover how nature works and to use that knowledge to make predictions about what is likely to happen in nature.

2. Science. Models, Systems “Scientific knowledge is a body of statements of varying degrees of certainty – some most unsure, some nearly sure, and none absolutely certain.” – Richard Feynman

3. Scientific Method

4. Experiments • Variables are what affect processes in the experiment • Controlled experiments have only one variable • Experimental group gets the variable • Control group does not have the variable • Can use placebos to make a blind/double-blind experiments

5. Inference • A reasonable explanation for an observation you have made • Based on your past experience and prior knowledge • Inferences are often changed when new observations are made • Observation: The grass on the school’s front lawn is wet. • Possible inferences: • It rained • The sprinkler was on • There’s dew on the grass • A dog peed on the grass

6. Inductive and Deductive Reasoning Inductive Reasoning Deductive Reasoning • Making general statements from specific facts or examples • Process of applying a general statement to specific facts or situations Anne: I've noticed previously that every time I kick a ball up, it comes back down, so I guess this next time when I kick it up, it will come back down, too. Claire: That's Newton's Law. Everything that goes up must come down. And so, if you kick the ball up, it must come down.

7. Theory and Law • Scientific Theory • A hypothesis that has been supported by multiple scientists’ experiments in multiple locations • A Scientific Law • A well-tested and widely accepted description of what we find happening repeatedly in nature in the same way

8. Scientific Laws • Law of Conservation of Matter • Matter can be changed from one form to another, but never created or destroyed. • Atomic Theory of Matter • All matter is made of atoms which cannot be destroyed, created, or subdivided.

9. Being a good scientist • Be skeptical • Look at evidence and evaluate it and related information and opinions  validate information • Identify and evaluate your personal assumptions, biases, and beliefs

10. Frontier and Consensus Science • Frontier/Tentative Science • Scientific “breakthroughs” and controversial data that have not been widely tested or peer reviewed • Vaccinations  autism • Consensus or Applied Science (Reliable Science) • Consists of data, theories, and laws that are widely accepted by scientists considered experts in the field involved • Earth is warming

11. Accuracy Vs. Precision Accuracy – measurement agrees with the accepted correct value Precision – measure of reproducibility

12. Science has limitations • Cannot prove/disprove anything absolutely • Scientists are human and have biases • Natural systems have lots of variables with complex interactions • Statistical tools must be made to make estimates • We’re limited to understanding the natural world

13. Matter and Energy Resources

14. Definitions • Matter– anything with mass and takes up space • Atomic Number - number of protons • Isotopes - same atomic number, different mass number • Ions - atoms can gain or lose one or more electrons • Mass Number - protons + neutrons

15. Building Blocks • atoms - smallest units of matter- protons, neutrons, electrons • ion - electrically charged atoms • molecules - combinations of atoms of the same or different elements

16. Isotope • Elements with same atomic number but a different mass number

17. Radioactive Isotopes • The nuclei of isotopes can be unstable  radioactive • Undergo radioactive decay – spontaneous release of material from the nucleus • Half-life = the time it takes for ½ of the original radioactive parent atoms to decay • Helps determine how long people and the environment must be protected from depleted nuclear fuel • Ex. Products of 235U have half lives of 10,000’s of years

18. Forms of Matter • elements – single type of atoms • 110 elements – 92 natural +18 synthesized • compounds - 2 or more elements, held together by chemical bonds

19. Some Important elements- composition by weight – only 8 elements make up 98.5% of the Earth’s crust

20. Organic Compounds • with ≥ 2 carbon atoms (and CH4) • Environmental examples: • Hydrocarbons = methane gas • Chlorinated hydrocarbons = DDT, PCB, Chlorofluorocarbons (CFC) • Simple carbohydrates = sugar, starch

21. Polymers • larger and more complex organic compounds made up of monomers • complex carbohydrates • proteins - 20 amino acids • nucleic acids – nucleotides

22. Inorganic compounds • Not originating from a living source • Earth’s crust – minerals, water • water, nitrous oxide, nitric oxide, carbon monoxide, carbon dioxide, sodium chloride, ammonia

23. 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

24. Law of Conservation of Matter • Elements and compounds changed from one form to another, can never be destroyed • No “away” in “throw away”

25. 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

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

27. Energy • Capacity to do work and transfer heat • Energy unit = joule (J) • Power = energy ÷ time  kilowatts (kW) • Kinetic Energy- energy in action • Heat – kinetic energy of moving atoms, ions, or molecules in a substance • Electromagnetic radiation – energy in the form of waves • Ex. a running river moves a turbine to produce power • Potential energy - stored energy that is potentially available • Ex. a dam stores water in a reservoir that can be released to move a turbine to produce power

28. Earth’s systems need energy • 99% solar  electromagnetic radiation • Indirectly produces wind, hydropower, and biomass • Without it earth’s temperature would be -240° C

29. Energy quality • Measure of how useful an energy source is in terms of concentration and ability (and ease of use) to perform work

30. 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 • Energy input always equal to energy output • Second Law of Thermodynamics • Energy always goes from a more useful to a less useful form when it changes from one form to another

31. Energy Efficiency • Ratio of the amount of work that is done to the total amount of energy that is introduced into the system in the first place • Ex. Coal-burning power plant • 1 metric ton of coal containing 24,000 mega joules (MJ) of chemical energy creates 8,400 MJ electricity • How efficient is the power plant? • 8,400/24,000 • 0.35  35% efficient • What percent of the original energy is “lost?” • 35%

32. Energy Efficiency • Transmission lines bring electricity from power plant to house • 10% of the electrical energy is lost • Transport is 10% efficient • Electrical energy is used to light an incandescent bulb • Bulb is 5% efficient  95% of energy is lost! • Overall: • .35 (power plant) x 0.9 (transmission lines) x 0.05 (light bulb) • What is the overall efficiency? • 0.016  1.6% efficiency

33. Systems Have Inputs, Flows, and Outputs • System • Set of components that interact in a regular way • Ex. Human body, earth, the economy • Inputs from the environment • Flows, throughputs of matter and energy • Outputs to the environment • Closed systems – no inputs or outputs • Ex. Earth • Energy system = open • Matter system = closed

34. Economic System Fig. 2-17, p. 48

35. 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

36. Positive Feedback Loop Fig. 2-18, p. 49

37. Negative Feedback Loop Fig. 2-19, p. 50

38. Complex systems • Time lags – change in a system leads to other changes after a delay • Ex. lung cancer • Synergy– when two or more processes interact so that the combined effect is greater • Helpful • Studying with a partner • Harmful • E.g., Smoking and inhaling asbestos particles • Chaos – unpredictable behavior in a system