Presentation on theme: "1 M11-P1 Materials from the Earth 6th International Junior Science Olympiad (IJSO) Dr. Yu-San Cheung Department of Chemistry The Chinese."— Presentation transcript:
1 M11-P1 Materials from the Earth 6th International Junior Science Olympiad (IJSO) Dr. Yu-San Cheung Department of Chemistry The Chinese University of Hong Kong
2 Naturally occurring substances Considered valuable in their relatively unmodified (natural) forms Values: depending on the amount available and the demand A 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 soil Biological resources - plants and animals Raw materials (like minerals) Space and land Energy (like wind, geothermal( 地熱的 ), tidal( 潮汐的 ), and solar energy) Natural Resources( 天然資源 )
3 They can restock (renew) themselves, be used indefinitely if they are not over-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 crops fish and livestock Examples of non-living renewable resources: fresh water fresh air Flow renewable resources (or simply “flow resources”): renewable, but needing no regeneration or re-growth e.g., wind, tidal, and solar energy Renewable Resources( 再生資源 )
4 A non-renewable resource 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. Non-renewable Resources ( 非再生資源 )
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, crabs, etc. Natural Resources and Their Products
6 “Periodic Chart.pdf” in Minerals and Their Chemical Components Exercise: Find out the major chemical content in various types of minerals
7 Common Minerals and Their Uses Exercise: Find out the uses of some common minerals.
8 Cement & Concrete Cement: made from limestone, calcium, silicon, iron, and aluminum, plus lesser amounts of other ingredients When water is added to cement, a chemical process occurs as it dries, allowing it to harden. Concrete: cement + aggregates (e.g., sand, stone) Important and widely-used construction material Strengthened by steel-rod skeleton Annual 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 ) 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 ) Aggregates and concrete Crushed and used as aggregates for new concrete Batteries Difficulty: so many types of batteries Some old types contain mercury and cadmium Lead-acid battery (mostly used in automobiles): containing lead Biodegradable waste Electronics waste (recovering metals) Various types of metals (e.g., _________________________________) Paper Glass Plastic Rubber Textiles Timber
11 Metals 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 electrons Most metals form ionic bonds with non-metals [but not always, e.g., in Pb(C 2 H 5 ) 4, there is Pb–CH 2 CH 3 covalent bond] Physical properties: Electrical conducting Some 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 of its components. Example The major component of steel is iron and steel is stronger than iron. If chromium is added, we have stainless steel which can resist corrosion.
13 Examples of Alloys Carbon steel: iron + carbon (higher carbon content, stronger but more brittle) - Low carbon steel: ~0.05 – 0.3% carbon content - Ultra-high carbon steel : ~1 – 2% carbon content Stainless steel: steel + chromium (> 10%) Brass: copper + zinc (typically ~30 – 35%) Bronze: copper + tin (typically 12%) Rose gold: gold + copper: for jewelry 24k: 100% gold (18k: 75% gold) (k = “karat”) Solder: Conventional: Sn60/Pb40 (60% tin + 40% lead) Lead-free: e.g., SnAgCu (tin + silver + copper); different SnAgCu compositions: different melting points
14 Energy Resources Solar energy Wind energy Water-related:hydro power pumped-storage tidal power wave power Geothermal energy Biomass energy Garbage energy Nuclear energy Fossil fuels
15 Generation of Electrical Energy( 電能 ) Electrical energy is easily transported (from power plants to individual customers) Electrical energy is versatile Majority of energy available from Nature: in the form of kinetic energy and heat energy Kinetic energy electrical energy Heat energy kinetic energy of steam kinetic energy of magnet/metal electrical energy
16 Lenz’s Law( 楞次定律 ) Faraday‘s Law( 法拉第定律 ) of Induction In effect: Changing magnetic field electrical current /Hbase/electric/farlaw.html That is, kinetic energy electrical energy
17 Turbine( 渦輪機 ) Flow of fluid (acting on blazes) rotation of shaft Kinetic energy of fluid kinetic energy of shaft electrical energy
18 Solar Energy( 太陽能 ) Energy from the Sun The Sun is a nuclear reactor, 150 million km away. Only a small fraction of light energy and heat energy (1 part in ) reaches the Earth, but it is a huge amount to the Earth. Ultra-violet(UV) Visible Infra-red (IR) Solar cell: light energy electrical energy Water-heating system: heat energy heat energy of water Solar furnaces: heat energy heat energy of gas kinetic energy of gas electrical energy “light” Absorbed and becoming heat energy Increasing wavelength
19 Exercise: How is solar energy used for heating water in Hong Kong? Example: ring07.pdf
20 Wind Energy( 風能 ) Energy from wind Ancient application: sailing Used since Middle Ages: windmill Electricity generation: wind turbine electricity (reverse of electric fan operation) Wind Propeller 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, war Used nowadays to generate 20% of the world’s electricity Reservoir Dam Turbine Generator
22 Pumped 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 not 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. Top Reservoir Turbines & Pumps Lower Reservoir
23 Tidal Power( 潮汐能 ) Tide: water movement, containing kinetic energy Twice a day 8 sites in Britain, generating 20% of energy needed ~20 potential sites in the world Largest one: northern France Tide coming inTide going out
24 Off-shore Station
25 Wave Power Wave: generated by wind on sea surface Method: reverse of a swimming pool wave machine Water level going up and down Air flowing in and out
26 Geothermal Energy( 地熱能 ) The centre of the Earth: ~6000 C hot enough to melt rock A few km down the surface: > 250 C Used for thousands of years in some countries for cooking and heating If hot enough to produce steam electricity If not: heating Cold water down Power station Hot water down Hot region
27 Biomass( 生物量 ) Energy from organisms (usually plants) Example: burning of wood for heat and light Extraction 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 ( 三酸甘油酯 ) (Esters of glycerol with long-chain fatty acids)
29 Use of Biodiesel in automobiles Recipe: Biodiesel from New Oil Example: 1994 Dodge: 100,000 miles on 100% Rapeseed ( 芥花籽 ) Biodiesel
30 Burning garbage: generating heat energy, but serious pollution (e.g., dioxin) Bacterial action: generating landfill gas (mainly methane, CH 4 ) Garbage Energy
31 Basis of Nuclear 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-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 by specific values of the atomic number (no. of protons) and the mass number (no. of protons and neutrons) 1 1 H 2 1 H 12 6 C 13 6 C Nuclides( 核素 )
35 Nuclei of some atoms, e.g., 40 K, are unstable. They undergo spontaneous transformation into more stable atoms. The substance is called 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 This radiation was later shown to be separable by electric (or magnetic) fields into three types: alpha ( ), beta ( ) and gamma ( ) 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) (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 )
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 structure Examples: inhibition of cell division, denature of enzymes, mutation of genetic materials Interaction of Radiation with Cells
40 Half-life (t 1/2 ): the time it takes for half of its original amount to decay 1 ½ ¼ 1/8 1/16 …. After n half-lives, 1/(2 n ) is left. For example, after 10 half- lives, 1/(2 10 ) = 1/1024 (about 0.1%) is left. Rate of Radioactive Decay
41 Radionuclide 81 Kr 38 K 73 Se 131 I 60 Co 137 Cs 14 C 129 I 235 U 40 K Half-life 13 seconds 7.6 min 7.2 hr 8 days 5.3 yr 30 yr 5730 yr 17 million yr 703 million yr 1260 million yr Each radionuclide has a characteristic t 1/2 Half-lives of Some Radionuclides
42 cosmic rays terrestrial radiation (including radon) food & drinks ( 40 K 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( 核燃料 ) 235 U + n 139 Ba + 94 Kr + 3n Characteristics: Bombarded by neutron Chain reaction: 1 neutron in, 3 neutrons out. But not every neutron can hit an 235 U nucleus. The reaction may eventually stop. n U 235 This neutron starts the chain reaction n n n Kr Ba U 235 n n n Kr Ba U 235 n n n Kr Ba U 235 n n n Kr Ba
44 Enriched Nuclear Fuel ( 核燃料 ) To make the chain reaction self-sustaining, we need to use: (1)uranium enriched in 235 U (2)super critical mass of the fuel Natural uranium: 238 U (99.3%) & 235 U (0.7%) Enriched: 2-3% in 235 U (>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% 235 U (~40 cm diameter) Higher 235 U percentage: larger/smaller critical mass Neutron reflector: larger/smaller critical mass
46 Nuclear Power Plant( 核能發電廠 ) Neutron absorber (e.g., boron, cadmium) Cooling Tower Cooling Water Condensor Turbine Generator Pumps Steam Line Steam Generator Reactor Containment Structure Control Rods
47 Other Nuclear Fuels Plutonium-239 & Uranium-233
48 Nuclear Fusion( 核聚變 ) Heavy nuclei favor fission. Light nuclei favor fusion. Examples of nuclear fusions: 2 H + 3 H 4 He + n 2 H + 2 H 3 He + n 2 H + 2 H 3 H + p
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 nuclear 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 2 H: 0.015%)
51 Accidents of Nuclear Power Plants Three Mile Island, USA (1979) Chernobyl, Ukraine, in former USSR (1986) Leakage of highly radioactive materials On the whole, non-nuclear large-scale industrial accidents result in higher tolls.
52 Nuclear Weapons & Nuclear Power Plants A nuclear power plant does not aim to make nuclear weapons. But the materials can be used for nuclear weapons. Concerns: 235 U: needs extra work to enrich its percentage 329 Pu: created in a uranium reactor, the percentage of which is high enough for nuclear weapons In addition to making a nuclear bomb (which can really explode), the waste can also used for “dirty bomb”. More about nuclear proliferation:
53 Advantages & Disadvantages Advantages No CO 2 is emitted No air is needed Disadvantages In case of accident, the damage is serious Using and producing materials, which are the source for nuclear weapons Disposal of nuclear waste: waste cannot be “destroyed”
54 Industrial Revolution: increases in the use of fossil fuels Steam engines (late 1700s): needed fuels chemical energy (stored in _______) heat energy (of _______) kinetic energy (of _______) kinetic energy (of _______) to run machines, cars, etc. Fossil Fuels( 化石燃料 )
55 What are fossil fuels? Plants, animals, and microorganisms (living millions of years ago) death Remains buried and subjected to high temperatures and pressures in Earth’s crust Primarily hydrocarbons, C x H y “Fossil fuel” sometimes also includes non-biological source such as tar sand, which is known as mineral fuel.
56 Coal Petroleum (oil) Natural gas Tar sands and oil shale Methane hydrate Types of Fossil Fuels( 化石燃料 )
57 Carbon Cycle Atmosphere ( ) Fossil Fuels & Cement Production ( ) Vegetation ( ) Soils ( ) Marine Biota ( ) Dissolved Organic Carbon ( ) Surface Ocean ( ) Deep Ocean ( ) Sediments ( ) Exercise: Find out the carbon distribution in the Nature from internet.
58 Heat Energy Units BTU (British Thermal Units) = 1054 – 1060 J Quad: quadrillion BTU = BTU Total U.S. energy use: ~100 Quad in 2005 A barrel of oil (bbl): ~6 million BTU 100 Quads: 17 billion barrels of oil (1 bbl = 42 gallons)
59 Coals( 煤 ) Plant remains covered by water and mud Readily combustible Black or brownish black in color Mainly composing of carbon, with an assortment of other elements (e.g., sulfur) Most abundant of all fossil fuels, the largest single source of fuel for the generation of electricity world-wide One of the major sources of carbon dioxide emissions
60 Worldwide Coal Production Exercise: Find out the worldwide coal production, coal reserves, and major coal exporters.
61 Processing of Coal Other than being burnt directly, coal can be further processed to obtain higher-quality fuel. Liquefaction: coal liquid fuels e.g., gasoline or diesel Gasification: C + steam + O 2 synthesis gas (CO + H 2 ) Coking (~ 1000 o C): driving off volatile substances to form coke
62 Petroleum( 石油 )(Oil, Crude Oil) Compression and heating of ancient organisms Buried at the ocean bottom, where O 2 was insufficient to oxidize all the organic materials
63 Oil Producing and Consuming Countries Exercise: Find out the major oil producing and consuming countries around the world.
64 Petroleum( 石油 ) Hydrocarbon, mostly alkane (saturated C x H y ): C 5 H 12 to C 18 H 38 Shorter hydrocarbon: natural gas Longer hydrocarbon: paraffin wax High energy density, easy transportability, relatively high abundance Source of raw material for many chemical products
65 Oil Refinery: Separating Components of Different Molecular Weights Very detailed flowchart: i/Image:RefineryFlow.png Exercise: Find out various oil refinery products and their usages.
66 Cracking( 裂解 ) Breaking down long carbon chains By heating & with catalysts e.g. CH 3 CH 2 CH 2 CH 3 CH 2 =CH 2 + CH 3 CH 3
67 Knocking of Gasoline( 汽油 ) Gasoline is burnt to produce energy in a combustion engine (e.g., of a vehicle) Some gasoline start to burn before they are ignited by sparks. This premature ignition produces a “knocking” sound. So it is sometimes called “knocking”. Consequences of knocking: power loss and engine wearing
68 Octane Rating Different gasoline have different anti-detonation Octane rating: a measure of the anti-detonation (or auto- ignition resistance) of gasoline and other fuels used in spark-ignition internal combustion engines.
69 iso-octane: set at 100 n-heptane: set at 0 A mixture of iso-octane and n-heptane: x% (by volume) in iso-octane, “octane rating”: x. Example: 84 liters of iso-octane + 16 liters of n-heptane 84% (by volume) in iso-octane 16% (by volume) in n-heptane Octane Rating: 84 It is found that 1-pentene has the same “knocking” property as this mixture, so we say that the octane rating of 1-pentene is 84. Octane Rating
70 Octane Rating Octane rating can be smaller than 0 and larger than 100. e.g., n-octane: -10 benzene: 101 ethane: 108 Octane rating for gasoline for vehicles:
71 Anti-knocking Agent Tetra-ethyl lead (TEL): Added to gasoline to increase octane rating About 0.05% of TEL in gasoline Pb(CH 2 CH 3 ) 4, mostly covalent in nature, not containing Pb 4+ and CH 2 CH 3 – How it works: Knocking causes formation of radicals, e.g., CH 3, from gasoline Chain reaction: these radicals destroy other gasoline molecules Pb(CH 2 CH 3 ) 4 Pb(CH 2 CH 3 ) 3 + CH 2 CH 3 (or Pb + 4 CH 2 CH 3 ?) These radicals from TEL and remove radicals from gasoline Sometime literatures say that Pb + O 2 PbO 2 and the PbO 2 reacts with the radicals from gasoline Other anti-knocking agents (also called octane enhancers): methanol & ethanol
72 Problems of Leaded Gasoline Lead is toxic to humans It poisons Rh and Pt catalysts in catalytic converters (which convert NOx and VOC emitted from pipes of vehicles into harmless substances) Rh = rhodium Pt = platinum Both are metals with catalytic property
73 Natural Gas( 天然氣 ) Formation process: similar to that of petroleum Components: (%) methane (CH 4 ): 70 – 90 ethane (C 2 H 6 ): 5 – 15 propane (C 3 H 8 ), butane (C 4 H 10 ): < 5 CO 2, N 2, helium, and hydrogen sulfide (H 2 S): balance Exercise: Find out the major natural gas producing and consuming countries around the world.
74 Tar Sand Also called “oil sand” (actually more appropriate) A mixture of extremely heavy crude oil, sand or clay, and water. Natural material, nothing to do with tar (man-made) Worldwide sources: Canada, Venezuela, and USA.
75 Oil Shale( 油頁岩 ) A fine-grained sedimentary rock containing significant traces of kerogen (a solid mixture of organic chemical compounds) that have not been buried for sufficient time to produce conventional fossil fuels. When heated to a sufficiently high temperature a vapor is driven off which can be distilled to yield a petroleum-like shale oil, a form of non-conventional oil, and combustible shale gas. Can be burnt directly as a low-grade fuel for power generation and heating. Can be used as a raw material in the chemical and construction materials industries. Reserve: mainly in North America
76 Methane Hydrate (Methane Ice) Ice that contains a large amount of methane within its crystal structure Total amount: billion tons of carbon (carbon for all fossil fuel reserves: 5000 billion tons) Natural gas hydrates (NGH) vs. liquefied natural gas (LNG) in transportation: NGH: stable up to −20 C LNG: stable up to −162 C Therefore, there is some interest in converting natural gas into NGH rather than LNG for transportation.