Chemistry - Unit 1

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  • Chemistry - Unit 1
    • 1. Fundamental Iedas
      • 1.1:  Atoms, Elements and Compounds - All material substances are made up of atoms; Elements are substances which contain only one type of atom; Compounds contain more than one different atom.
        • NOTE: The word 'atom' comes from the Greek 'atomos' meaning indivisible, as atoms cannot be (safely) split into anything smaller.
        • NOTE: Atoms consist of +ve protons and +-ve neutrons in the nucleus, with -ve electrons in outer levels.
      • 1.2: Atomic Structure - Atoms are made of protons, electrons and neutrons; protons have a +ve charge whilst electrons have -ve, equalling it out; Neutrons have a neutral charge; Atomic no. is the count of p+ in an atom (and also e- in a non-ion); Mass no. is the added mass of p+ and n0 (e- are not counted as they are too small to make a difference).
        • NOTE: Neutrons have a neutral0 charge as they are a proton and an electron together. The +ve and -ve charges cancel each other, creating neutral0 charge.
        • NOTE: Electrons are NOT equal in mass (they're actually 1/1836) to a proton (composed of 2 up and 1 down). The energy binding these three quarks is what makes the proton so massive. However if an e- is -1, ups are +2/3 and downs +1/3, making a +1 - equal to the e-.
      • 1.3: Arrangement of Electrons - Electrons are arranged in energy levels or 'shells'; Atoms with the same no. of e- in the outer shell are in the same group (1 - 8); The group number determines the properties (melting/boilng point, reactivity, rarity, etc.) of the atom.
        • NOTE: The fact that the nucleus takes up most of the mass in an atom, yet only a fraction of the space, infers (disturbingly) that the majority of matter is just empty space.
      • 1.4: Forming Bonds - When atoms from different elements react together, compounds are formed; Metal atoms form +ve charged ions; Non-metals form -ve charged ions; These +ve and -ve ions are attracted and bond; Non-metals bond together by sharing e- in covalent bonding.
        • NOTE: A compound's formula (eg. CaCO3) shows how many of which atom have bonded to make that compound.
      • 1.5: Chemical Equations - As no atoms are created or destroyed  in a chemical reaction the mass of reactants must equal the mass of the product(s); There must be the same number of each type of atom on each side of an equation.
    • 2. Rocks and Limestone Building Materials
      • 2.1: Limestone and Uses - Limestone is made from CaCO3; It is widely used in the building industry; The CaCO3 in limestone breaks down in thermal decomposition to make Ca and CO2.
      • 2.2: Reactions in Carbonates - Carbonates react with dilute acid to form a salt, water and carbon dioxide; Limewater turns cloudy in the test for CO2. A precipitate of insoluble CaCO3 causes the cloudiness; Metal carbonates decompose on heating to form metal oxides and carbon dioxide.
        • NOTE:    Acid + Metal -> Salt + Hydrogen;                   Acid + Metal Oxide -> Salt + Water;                    Acid + Metal Carbonate -> Salt + Water + Carbon Dioxide.
      • 2.3: Limestone Cycle - When water is added to CaO it produces CaOH; CaOH is alkaline so it can be used to neutralise acids; The reaction and formation of limestone is called the limestone cycle.
        • NOTE: CaCO3 -heat-> CaO + CO2;                         CaO -water-> CaOH;                            CaOH -more-water-and-filter-> CaOH (sol);                      -add-CO2-> CaCO3
      • 2.4: Cement and Concrete - Cement is made by heating clay mixed with crushed limestone powder in a kiln; Mortar is made by mixing cement and sand with water; Concrete is made by mixing aggregate  with cement, sand and water.
      • 2.5: Limestone and Issues - Limestone quarrying has advantages and disadvantages - job creation, local income, increased traffic, scarred landscape, affected habitat; limestone, cement, mortar and concrete all have useful properties in construction, glass-making and sculpture, meaning demand will always be high.
        • NOTE: The UK luckily has some of the greatest limestone reserves on Earth, meaning it is a leader in quarrying, production and exportation of limestone and calcium oxide.
    • 3. Metals and Uses
      • 3.1: Extracting Metals - A mined metal which is economically viable to extract is called an ore; Ores need to be concentrated to make the metal:waste ratio higher; nonreactive metals like gold and platinum are found pure, meaning they need less extraction; All metals below Carbon in the reactivity series can be reduced with Carbon to give the metal.
      • 3.2: Iron and Steels - Iron is extracted from iron ore by reduction in a blast furnace; pure iron is too soft and malleable for it to be useful; carefully controlled quantities of carbon and other elements are added to iron to make steel alloys; common steels eg. low-carbon, which is easily shaped and stainless, which is resistant to corrosion.
        • NOTE: The Angel of the North, standing at 20m with a wingspan of 54m and weighing over 200 tonnes, is made from a copper and iron based steel. The tallest statue in the world is The Spring Temple Buddha in Henan, China, consisting of 1125 pieces of copper cast and weighing over 1,000 tonnes.
      • 3.3: Aluminium and Titanium - Both are useful because they are corrosion resistant; Al has to be extracted using electrolysis as it is higher than C in the reactivity series; Both Al and Ti are expensive as their extraction requires many stages and huge amounts of energy.
      • 3.4: Extracting Copper - Most copper is extracted by smelting (also known as roasting) copper-rich ores, although our limited supplies of ores are becoming scarcer and scarcer; Copper can be extracted from copper solutions by electrolysis or by displacement using scrap iron. Electrolysis is also used to purify impure copper.
        • NOTE: Fibre optic cables have been developed as a replacement for copper wires, many of them transatlantic and other undersea cables, as the metal will soon run out. Fibre optics are also a good alternative as they can carry more than one piece of information per place.
        • NOTE: Biologists are developing new ways to extract low-grade, cheap copper using organic methods such as bacterial bioleaching and plants in phytomining.
      • 3.5: Useful Metals - The transition metals are found in the central block of the periodic table; they have properties that make them useful for construction and design - eg. copper wiring is used because of its high conductivity; copper, gold, aluminium and iron are all alloyed with other metals to make them stronger and less malleable.
        • NOTE:  Rare Earth metals such as gold can be found all over, such the reasonable deposits in Wales, but the quantity is not enough to make its extraction industrious. In modern times, Welsh gold has been used to make the wedding rings of royal brides and other royal jewelry.
        • NOTE: Alloys are far less malleable as they are composed of different sized atoms, meaning they cannot move about as freely as in pure element, where all the atoms are structured and the same size. This raises the boiling and melting points of the alloy considerably.
      • 3.6: Metallic Issues - There are many issues regarding the mining and exploiting metal ores and the Earth's deposits; Recycling metals saves energy and finite resources. The pollution from extraction is also reduced; Metals are not completely ideal construction materials as they can rust and are expensive.
        • NOTE: Another organic way of removing pure metals is by allowing plants to absorb the metal and recovering the metal from the ashes of the plants.
    • 4. Crude Oils and Fuels
      • 4.1: Fuels from Crude Oils - Crude oil is a mixture of many different compounds; Many of the compounds are hydrocarbons; alkanes are saturated hydrocarbons - they carry as many hydrogen atoms as possible in their molecules.
        • NOTE: Hydrocarbons are simply any polymer containing both (and only) hydrogen and carbon atoms in their molecules.
      • 4.2: Fractional Distillation (Of oil! Not booze) - Crude oil is fractionalised down into small chains by distillation; The properties of each fraction depends on the size of the hydrocarbon molecules; smaller chains make better fuels as they ignite more easily and burn well, with smokeless flames.
      • 4.3: Burning Fuels - When hydrocarbons are burnt in plenty of air, the carbon and hydrogen in the fuel are completely oxidised, producing carbon dioxide and water; If they are burnt in insufficient oxygen it forms poisonous carbon MONoxide and soot; Sulphur impurities in fuels burn to form sulphur dioxide which causes acid rain; At high temperatures in combustion engines nitrogen from the air reacts with oxygen to form nitrogen oxides, which too cause acid and also breathing problems for some people.
        • NOTE: Sulphur can be spelt with either an 'f' or a 'ph', depending on whether the Latin 'p' or Greek 'theta' is taken as the true root. Although 'Sulfur' was established as the international spelling in 1990, as the USA deliberately chose the Greek form, many British and European publishers and institutions still use 'ph'.
      • 4.4: Cleaner Fuels - Burning fuels release substances that spread throughout the atmosphere; The pollution produced by burning fuels can be reduced by treating the pollutants from combustion. This removes nitrogen oxides, sulphur dioxides and carbon monoxide; sulphur can also be removed from fuels before they are even burnt.
        •   NOTE: Carbon dioxide and other gases produced in combustion are labelled 'greenhouse gases' as they have been shown to cause global temperatures to rise unchecked. It destroys the ozone, allowing greater UV exposure from Sol, and also absorbs radiation bouncing off Earth and back into space, creating a blanket effect, such as on Venus.
      • 4.5: Alternative Fuels  - Biofuels are a renewable source of energy that could eventually replace all fossil fuels; Biodiesel can be made from vegetable oils; There are both advantages and disadvantages of using biodiesel; Ethanol is another biofuel that is made from sugar plants; biogas generators create energy from the gas produced by rotting and decomposing organic matter.
        • NOTE: Hydrogen is the main alternative to fossil fuels at the moment. As the most abundant element in the Universe, and easily creatable, it will certainly never in short supply. The problem is in the amount of energy expended extracting it into fuel form and also in creating special hydrogen fuel cells.
    • 5. Products from Oils
      • 5.1: Cracking Hydrocarbons - Hydrocarbons can be split by mixing the chains with steam and heating to a high temperature or by passing the vapours over a heated catalyst; cracking produces saturated hydrocarbons which are used as fuels and unsaturated hydrocarbons called alkenes.
        • NOTE: Alkenes can be reacted with an alkene indicator - orange bromine water which turns it colourless, proving the presence of saturates.
      • 5.2: Making Polymers from Alkenes - All plastics are a type of material called polymers, which are large chains of molecules reacted together; Singular molecules are called monomers.
        • NOTE: 'Polymer' literally means 'many-molecules', taken from the Greek 'poly-'; 'Monomer' inversely means 'single-molecule', using the Greek number one - 'mono-' - as the prefix.
      • 5.3: New and Useful Polymers - New polymers are being developed all the time - they are specially designed to have certain properties that make them suited for certain uses; Smart polymers may have their properties changed by light, temperature, age or other surroundings. This allows them to react to circumstances; More plastics are now being recycled with government and international emphasis on sustainable living.
      • 5.4: Plastic Waste - Non-biodegradable plastics cause unsightly rubbish, take up space in landfill and are a huge threat to land and marine wildlife; Biodegradable plastics are decomposed by the action of microorganisms in soil. Making plastics with starch granules in their structure help the microorganisms break down plastic.
      • 5.5: Ethanol - There are two ways of producing ethanol: one for industrial use and one for human consumption; Ethene passed over steam in the presence of a catalyst forms cheap, pure and quick ethanol in a continuous process called hydration; The more traditional batch process produces ethanol by fermenting sugar (glucose) using carbon dioxide.
    • 6. Plant Oils
      • 6.1: Extracting Vegetable Oils - Vegetable oils can be extracted from seeds, nuts and fruits by pressing or distillation; Vegetable oils provide nutrients and a lot of energy. They are important foods and can be used to make biofuels.
        • NOTE: Unsaturated oils contain carbon-carbon double bonds (C=C) and so decolourise bromine water.
      • 6.2: Cooking With Vegetable Oils - Vegetable oils are useful in cooking because of their high boiling point, meaning they won't evaporate in normal cooking temperatures; Cooking in oil increases the energy content of foods, changes the flavour, colour and texture of the food.
        • NOTE: Vegetable oils can be hardened by reacting them with hydrogen at 60 degrees C with a nickel catalyst. This makes them solids at room temperature that are suitable for spreading (Margerine, Flora).
      • 6.3: Everyday Emulsions - Oils do not dissolve in water but oils and water can be used to produce emulsions which all have special properties; Emulsions made from vegetable oils are used in many foods; Because they have molecules which are both hydrophobic and hydrophilic at opposite ends, they stop oil and water separating into layers as they usually would.
        • NOTE: Foods which contain emulsifiers include ice cream, mayonnaise, coffee and butterfat.
      • 6.4: Food Issues - Vegetable oils are high in energy and provide nutrients; Vegetable oils are believed to be better for health than saturated fats; Emulsifiers improve the texture of foods enabling water and oil to mix. This makes fatty foods more palatable and tempting to eat; Any substance added to a food to preserve it or improve its taste, texture or appearance is called an additive.  
        • NOTE: Additives that have been approved for use in Europe are given E numbers (usually with a negative stigma attached).
    • 7. The Changing Earth
      • 7.1: Structure of the Earth - The Earth is made of layers called the inner core, outer core, mantle, upper mantle, and crust, with the atmosphere around the surface; The Earth's limited resources come from the crust, oceans, atmosphere and immediate neighbouring bodies.
      • 7.2: The Restless Earth - The crust and upper mantle are split into tectonic plates which are constantly moving because of convection currents in the mantle caused by radioactive decay; Earthquakes, volcanoes and mountain ranges occur along fault lines - where tectonic plates meet - but it is difficult to accurately predict where and when earthquakes will occur.
        • NOTE: The theory of tectonic plates and continental drift was first proposed by Alfred Wegener in 1912, and repeated in his first book in 1915, but it took until the 1960s, 30 years after Wegener's death on an Arctic supply mission that it was fully accepted.
      • 7.3: The Earth's Atmosphere - The Earth's atmosphere was formed by early volcanic activity, releasing sulphur, carbon dioxide, methane and ammonia; Oxygen was added by early life taking in CO2 and releasing Oxygen - which eventually became so concentrated that it was poisonous to the plants, wiping them out and allowing new life forms better adapted to oxygen to become the dominant strain.
      • 7.4: Life on Earth (No, not the TV programme!) - There are many theories on how life began on Earth, some with more credibility than others; The most famous is Miller-Urey's idea of a hydrocarbon, ammonia and (most importantly) protein 'primordial soup' with lightning providing energy, creating the first lifeforms.
        • NOTE: The general scientific consensus of life's beginning is that it was at least 4 billion years ago; multi-cellular lifeforms appeared around 2.9 billion years ago; and complex life appeared after the Cambrian Explosion 542 million years ago.
        • NOTE: Other theories propose:                         - life was formed on the ocean floor, not the surface, around thermal vents giving out sustaining chemicals and carbon-dioxide, known as the Deep Sea Vent theory                     - that life (or the basic ingredients at least) was brought to Earth during the Late Bombardment on asteroids and comets, of which there is significant evidence to support (however, this just shifts responsibility elsewhere, not actually explaining how the bacteria 'became')                              - that the first lifeforms were created by extra-terrestrial life and evolution and society has been guided by them ever since (again, not explaining just shifting the responsibility)                        - and also that life was created by extra-Universal higher being(s), found in many cultures and Creation stories across the globe.
      • 7.5: Gases in the Atmosphere - Most of the CO2 in the early atmosphere became locked up in sedimentary rocks and fossil fuels; Today's atmosphere is 78% nitrogen, 21% oxygen, 0.9% argon, 0.035% carbon dioxide and the rest is trace gases; The main gases can be separated  by fractional distillation and used in industry as raw materials.
      • 7.6: Carbon Dioxide in the Atmosphere - 0.035% (or 350 ppm) of Earth's atmosphere is Carbon Dioxide; Carbon moves into and and out of the atmosphere due to plants, animals, oceanic circulation and sedimentary rocks; The amount of CO2 in the atmosphere has risen noticeably in the recent past due to fossil fuels being burnt and released into the atmosphere.

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