1、1,M11-P1 Materials from the Earth,6th International Junior Science Olympiad (IJSO),Dr. Yu-San Cheungyscheungcuhk.edu.hkDepartment of ChemistryThe Chinese University of Hong Kong,2,Naturally occurring substancesConsidered valuable in their relatively unmodified (natural) formsValues: depending on the
2、 amount available and the demandA commodity is generally considered a natural resource when the primary activities associated with it are extraction and purification, as opposed to creation.Examples of natural resources:Air, water, and soilBiological resources - plants and animals Raw materials (lik
3、e minerals) Space and land Energy (like wind, geothermal(地熱的), tidal(潮汐的), and solar energy),Natural Resources(天然資源),http:/en.wikipedia.org/wiki/Natural_resources,http:/www.ecofriendlykids.co.uk/NaturalResourcesEarth.html,3,They can restock (renew) themselves, be used indefinitely if they are not ov
4、er-harvested.If consumed at a rate that exceeds their natural rate of replacement, the standing stock will diminish and eventually run out. Examples of living renewable resources: trees (forests and woodlands) and cropsfish and livestockExamples of non-living renewable resources: fresh waterfresh ai
5、rFlow renewable resources (or simply “flow resources”):renewable, but needing no regeneration or re-growthe.g., wind, tidal, and solar energy,Renewable Resources(再生資源),http:/en.wikipedia.org/wiki/Natural_resources,http:/www.ecofriendlykids.co.uk/NaturalResourcesEarth.html,4,A non-renewable resource
6、is a natural resource that cannot be re-made, re-grown, or regenerated on a scale comparative to its consumption. Fossil fuels, such as coal, petroleum, and natural gas are often considered non-renewable resources, as they do not naturally re-form at a rate that makes the way we use them sustainable
7、.,Non-renewable Resources (非再生資源),http:/en.wikipedia.org/wiki/Natural_resources,5,Forests: timber (for building houses, boats, decks, and furniture; and making paper) Mines: metal products, fossil fuels, salts, jewelry, gravel (for building roads and concrete)Aquaculture(水產養殖): fishes, shrimps, crab
8、s, etc.,Natural Resources and Their Products,http:/www3.iptv.org/exploremore/land/issues/iss_natu/natural_resources.cfm,6,“Periodic Chart.pdf” in http:/www.mii.org/,Minerals and Their Chemical Components,Exercise: Find out the major chemical content in various types of minerals,7,Common Minerals and
9、 Their Uses,http:/www.mii.org/commonminerals.html,Exercise:Find out the uses of some common minerals.,8,Cement & Concrete,http:/ from limestone, calcium, silicon, iron, and aluminum, plus lesser amounts of other ingredientsWhen water is added to cement, a chemical process occurs as it dries, allowin
10、g it to harden. Concrete:cement + aggregates (e.g., sand, stone)Important and widely-used construction materialStrengthened by steel-rod skeletonAnnual production: about 6 billion tons (1 ton each person on the Earth)Life: 50,000 years,Cement: 水泥Concrete:混凝土,9,Recycling(循環),http:/en.wikipedia.org/wi
11、ki/Recycling,Recycling is the reprocessing of materials into new products.It can save energy and reduce air pollution.,Exercise: Find out the environmental effects of recycling.,10,Recycling (循環),http:/en.wikipedia.org/wiki/Recycling,Aggregates and concreteCrushed and used as aggregates for new conc
12、reteBatteriesDifficulty: so many types of batteriesSome old types contain mercury and cadmiumLead-acid battery (mostly used in automobiles): containing leadBiodegradable wasteElectronics waste (recovering metals)Various types of metals (e.g., _)PaperGlassPlasticRubber TextilesTimber,11,Metals,http:/
13、en.wikipedia.org/wiki/Metal,In chemistry:A metal is an element that readily loses electrons to form positive ions (cations) and the cations are surrounded by a sea of electronsMost metals form ionic bonds with non-metals but not always, e.g., in Pb(C2H5)4, there is PbCH2CH3 covalent bondPhysical pro
14、perties:Electrical conductingSome hard, some soft, some being liquid,12,Alloys(合金),Alloy: a homogeneous mixture of two or more elements, at least one of the elements is a metal, the resulting mixture has metallic properties.An alloy usually has properties (physical and chemical) different from those
15、 of its components.ExampleThe major component of steel is iron and steel is stronger than iron.If chromium is added, we have stainless steel which can resist corrosion.,http:/en.wikipedia.org/wiki/Alloy,13,Examples of Alloys,http:/en.wikipedia.org/wiki/Carbon_steelhttp:/en.wikipedia.org/wiki/Stainle
16、ss_steelhttp:/en.wikipedia.org/wiki/Brasshttp:/en.wikipedia.org/wiki/Bronzeshttp:/en.wikipedia.org/wiki/Rose_goldhttp:/en.wikipedia.org/wiki/Solderhttp:/en.wikipedia.org/wiki/List_of_alloys,Carbon steel: iron + carbon (higher carbon content, stronger but more brittle)- Low carbon steel: 0.05 0.3% ca
17、rbon content- Ultra-high carbon steel : 1 2% carbon contentStainless steel: steel + chromium ( 10%)Brass: copper + zinc (typically 30 35%)Bronze: copper + tin (typically 12%)Rose gold: gold + copper: for jewelry24k: 100% gold (18k: 75% gold) (k = “karat”)Solder: Conventional: Sn60/Pb40 (60% tin + 40
18、% lead)Lead-free: e.g., SnAgCu (tin + silver + copper); different SnAgCu compositions: different melting points,14,Energy Resources,Solar energyWind energyWater-related:hydro power pumped-storagetidal power wave power Geothermal energyBiomass energyGarbage energyNuclear energyFossil fuels,http:/ of
19、Electrical Energy(電能),Electrical energy is easily transported (from power plants to individual customers)Electrical energy is versatileMajority of energy available from Nature: in the form of kinetic energy and heat energyKinetic energy electrical energy Heat energy kinetic energy of steam kinetic e
20、nergy of magnet/metal electrical energy,16,Lenzs Law(楞次定律)Faradays Law(法拉第定律) of Induction,In effect: Changing magnetic field electrical current,http:/hyperphysics.phy-astr.gsu.edu /Hbase/electric/farlaw.html,That is, kinetic energy electrical energy,17,Turbine(渦輪機),Flow of fluid (acting on blazes)
21、rotation of shaftKinetic energy of fluid kinetic energy of shaft electrical energy,http:/en.wikipedia.org/wiki/Turbine,18,Solar Energy(太陽能),Energy from the SunThe Sun is a nuclear reactor, 150 million km away. Only a small fraction of light energy and heat energy (1 part in 1010) reaches the Earth,
22、but it is a huge amount to the Earth.Ultra-violet(UV) Visible Infra-red (IR)Solar cell: light energy electrical energyWater-heating system: heat energy heat energy of waterSolar furnaces: heat energy heat energy of gas kinetic energy of gas electrical energy,http:/ and becoming heat energy,Increasin
23、g wavelength,19,Exercise: How is solar energy used for heating water in Hong Kong? Example: http:/www.cuhk.edu.hk/greencampus/en/communication/sc_spring07.pdf,20,Wind Energy(風能),Energy from windAncient application: sailingUsed since Middle Ages: windmillElectricity generation: wind turbine electrici
24、ty(reverse of electric fan operation),http:/ blades,Gearbox & generator in housing which can be rotated to face the wind,Tower,21,Hydro Power(水力),Energy from the flow of water: (potential energy of water kinetic energy of water ) Ancient application: corn grinding, sailing, warUsed nowadays to gener
25、ate 20% of the worlds electricity,http:/ Storage Reservoirs,They are not facilities or methods to generate electrical power. They are a way of storing energy so that it can be released quickly when needed. Demand for electrical power changes throughout the day. When the demand is low, extra power no
26、t used is wasted.,A facility is needed which can store excess energy produced, and can release the stored energy immediately. Pumped storage reservoirs can do the job.,http:/ & Pumps,Lower Reservoir,23,Tidal Power(潮汐能),Tide: water movement, containing kinetic energyTwice a day8 sites in Britain, gen
27、erating 20% of energy needed 20 potential sites in the worldLargest one: northern France,http:/ coming in,Tide going out,24,Off-shore Station,http:/www.swanturbines.co.uk/,http:/ Power,Wave: generated by wind on sea surfaceMethod: reverse of a swimming pool wave machine,http:/ level going up and dow
28、n,Air flowing in and out,26,Geothermal Energy(地熱能),The centre of the Earth: 6000 Chot enough to melt rockA few km down the surface: 250 CUsed for thousands of years in some countries for cooking and heating,If hot enough to produce steam electricityIf not: heating,http:/ water down,Power station,Hot
29、 water down,Hot region,27,Biomass(生物量),Energy from organisms (usually plants)Example: burning of wood for heat and lightExtraction of fuel: ethanol by fermentation: corns / canes cane sugar ethanol Biodiesel: a fuel made from vegetable oil that runs in any unmodified diesel engine.,Triglycerides (三酸
30、甘油酯)(Esters of glycerol with long-chain fatty acids),28,Triglycerides Biodiesel,29,Use of Biodiesel in automobiles,Recipe: Biodiesel from New Oil,Example:1994 Dodge: 100,000 miles on 100% Rapeseed (芥花籽),http:/www.dancingrabbit.org/biodiesel/newoil.php,Biodiesel,30,Garbage Energy,31,Basis of Nuclear
31、Physics & Nuclear Power,32,Testing your knowledge on: molecules, atoms, and subatomic particles,A molecule consists of two or more _ of the same or different elements. Examples: _Atoms are the smallest particles of an element.Sub-atomic particles: particles that constitute atoms. _Which of these sub
32、-atomic particles make up nuclei?,33,Compare the sizes of:molecules, atoms, and nuclei.,Testing your knowledge on: molecules, atoms, and subatomic particles,Isotopes are atoms of the same _ but having different numbers of _ in their _.,Exercise (fill-in-the-blank):,34,A nuclear species characterized
33、 by specific values of the atomic number (no. of protons) and the mass number (no. of protons and neutrons),mass number,atomic number,element symbol,Nuclides(核素),35,Nuclei of some atoms, e.g., 40K, are unstable. They undergo spontaneous transformation into more stable atoms. The substance is called
34、radioactive.Such a transformation process is called radioactive decay. It is usually accompanied by emitting particles and energy collectively called radiation.,Radioactive(放射性)Substances,36,The phenomena of radioactivity was discovered in 1896. This radiation was later shown to be separable by elec
35、tric (or magnetic) fields into three types: alpha (a), beta (b) and gamma (g) rays.,Radioactivity(放射現象),Radioactive material,+,Lead block,Electric plate (negative),Electric plate (positive),Luminescent screen,ray, ray, ray,37,Unstable nuclei are radioactive Nuclei consist of proton(s) & neutron(s) (
36、except _) Forces inside the nuclei: (1) Repulsive Coulomb force: between protons (2) Attractive nuclear force: between proton & proton, neutron & neutron, proton & neutron Stability depends on the balance of the two forces,Stability of Nuclides(核穩定性),38,Alpha particle (helium-4 nucleus, 4He2+) Beta
37、particle (electron) Gamma ray / X-ray (electromagnetic radiation) Neutron,Radioactive Decay Products,39,Ionization and atomic excitation causing molecular rearrangement or formation of free radicals Alteration of molecules leads to malfunction of physiological processes which depend on the chemical
38、structure Examples: inhibition of cell division, denature of enzymes, mutation of genetic materials,Interaction of Radiation with Cells,40,Half-life (t1/2): the time it takes for half of its original amount to decay,1 1/8 1/16 .,After n half-lives, 1/(2n) is left.For example, after 10 half-lives, 1/
39、(210) = 1/1024 (about 0.1%) is left.,Rate of Radioactive Decay,41,Radionuclide81Kr38K73Se131I60Co137Cs14C129I235U40K,Half-life13 seconds7.6 min7.2 hr8 days5.3 yr30 yr5730 yr17 million yr703 million yr1260 million yr,Each radionuclide has a characteristic t1/2,Half-lives of Some Radionuclides,42,cosm
40、ic rays terrestrial radiation (including radon) food & drinks (40K within body),medical instruments leakage/disposal radioactive fallout (weapon testing) consumer products, e.g., smoke detectors, “glow in the dark” watches,Sources of Radiation,Natural Radiation,Artificial Radiation,43,Nuclear Fuel(核
41、燃料),235U + n 139Ba + 94Kr + 3n,Characteristics: Bombarded by neutron Chain reaction: 1 neutron in, 3 neutrons out.But not every neutron can hit an 235U nucleus.The reaction may eventually stop.,http:/ Nuclear Fuel(核燃料),To make the chain reaction self-sustaining, we need to use:uranium enriched in 23
42、5Usuper critical mass of the fuelNatural uranium: 238U (99.3%) & 235U (0.7%)Enriched: 2-3% in 235U (85% for bomb)Methods: centrifugation, diffusion, and electromagnetic isotopic separation.,45,Critical Mass(臨界質量),Critical mass: sphere of 600 kg for 15% 235U (40 cm diameter)Higher 235U percentage: la
43、rger/smaller critical massNeutron reflector: larger/smaller critical mass,http:/en.wikipedia.org/wiki/Image:Critical_mass.svg,46,Nuclear Power Plant(核能發電廠),http:/ Nuclear Fuels,Plutonium-239 & Uranium-233,48,Nuclear Fusion(核聚變),Heavy nuclei favor fission.Light nuclei favor fusion.Examples of nuclear
44、 fusions:2H + 3H 4He + n 2H + 2H 3He + n2H + 2H 3H + p,http:/en.wikipedia.org/wiki/Nuclear_fusion,49,Human-made Nuclear Fusion,In order for a nuclear fusion to occur, two nuclei must be brought close enough.But the repulsion between nuclei is huge. Nuclei must contain high enough energy.Human-made n
45、uclear fusion: through nuclear fission in nuclear bomb,50,Nuclear Fusion(核聚變) in Nuclear Power Plant,Nuclear fusion: more energy released than fission But once started, nuclear fusion is out of controlled and cannot be stopped.Nuclear fusion for power generation: to be developed.Other advantages of fusions over fissions: less hazardous products source more available (natural abundance of 2H: 0.015%),
