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

Science and Technology

Science – knowledge of how the world worksTechnology – creation of new processes intended to improve the quality of life

Scientific methodHYPOTHESIS – proposed to explain observed patternsCritical experimentsAnalysis and conclusions

Scientific law and Theory

Law – certain phenomena always act in a predictable mannerTheory – rational explanation for numerous observations of a certain phenomena – global warming due to greenhouse effect

Accuracy Vs PrecisionAccuracy – measurement agrees with the accepted correct value

Precision – measure of reproducibility

Types of reasoningInductive - using observations and facts to arrive at generalizationsDeductive - using logic to arrive at a specific conclusion

ModelsMental models –perception , unreliableConceptual – general relationships among components of a systemGraphic – display dataPhysical – miniaturesMathematical – use of equations

Feedback loop Change in one part of a system influences another part of the system

Positive feedback loopExponential growth of population – more individuals lead to increased number of births

Negative feedback loopTemperature regulation in humans – increased temperature leads to decrease in temperature by sweating

Complex systemsTime lags – change in a system leads to other changes after a delay – lung cancerResistance to change – built in resistance – political, economicSynergy-when two or more processes interact so that the combined effect is greater Chaos – unpredictable behavior in a system

Gaia Hypothesis (1970)

James Lovelock and Lynn Marguilisproposes that organisms interact with their inorganic surroundings on Earth to form a self-regulating, complex system that contributes to maintaining the conditions for life on the planet

Important TermsInputs - matter, energy, informationThroughput - flow of inputOutput - matter, energy, information flowing out

Matter and Energy ResourcesNature’s Building Blocksanything that has mass and takes up space

Forms of matterelements – single type of atoms110 elements – 92 natural +18 synthesizedcompounds - 2 or more elements, held together by chemical bonds

Building Blocksatoms - smallest units of matter- protons,neutrons,electronsion - electrically charged atomsmolecules - combinations of atoms of the same or different elements

DefinitionsAtomic Number - number of protonsIsotopes - same atomic number, different mass numberIons - atoms can gain or lose one or more electronsMass Number - protons + neutrons

IsotopeElements with same atomic number but a different mass number

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

Organic Compoundswith carbonsugar, vitamins, plastics, aspirin

Environmental Organic Compounds

Hydrocarbons = methane gasChlorinated hydrocarbons =. DDT, PCBChlorofluorocarbons (CFC)- Freon 12

Polymerslarger and more complex organic compounds made up of monomerscomplex carbohydratesproteins - 20 amino acidsnucleic acids - nucleotides

Inorganic compoundsno carbon,not originating from a living sourceEarth’s crust – minerals,waterwater, nitrous oxide, nitric oxide, carbon monoxide, carbon dioxide, sodium chloride, ammonia

Matter qualityMeasure of how useful a matter is for humans based on availability and concentration

Energycapacity to do work and transfer heat Kinetic Energy -energy in actionelectromagnetic radiation, heat, temperaturePotential energy - stored energy that is potentially available

Electromagnetic radiationdifferent wave lengths shorter – high energy, disrupts cells with long term exposure

Energy sources97% solarwithout it earth’s temperature - 240 C1% - non commercial(wood, dung, crops) + commercial ( burning mineral resources)

Energy qualityMeasure of how useful an energy source is in terms of concentration and ability to perform useful work

Law of Conservation of Matter

elements and compounds changed from one form to another, can never be destroyedno “away” in “throw away”

Nuclear Changesnuclei of certain isotopes spontaneously change (radioisotopes) or made to change into one or more different isotopes Alpha particles – fast moving (2 protons+2neutrons); Beta particles – high speed electrons ; Gamma particles - high energy electromagnetic radiation radioactive decay, nuclear fission, nuclear fusion

Use….radioisotopesEstimate age of rocks and fossilsTracers in pollution detection and medicineGenetic control of insects

Half - Lifetime needed for one-half of the nuclei in a radioisotope to decay and emit their radiation. Goes through 10 half –lives before it becomes a non-radioactive form

Nuclear Fissioncertain isotopes

(uranium 235) split apart into lighter nuclei when struck by neutronschain reaction releases energyneeds critical mass of fissionable nuclei

Nuclear fusiontwo isotopes (hydrogen) forced together at extremely high temperatures (100 million C)uncontrolled nuclear fusion thermonuclear weapons

1st Law of Energy or 1st Law of Thermodynamics

in all physical and chemical changes energy is neither created or destroyedenergy input always equal to energy output

2nd Law of Energy or 2nd Law of Thermodynamics

when energy is changed from one form to another some of the useful energy is always degraded to lower quality, more dispersed, less useful energy(heat)

Implications for the environment – High waste society

Implications for the environment – Low waste society