- Created by: Anna Fox
- Created on: 05-01-12 19:06
Lime cycle, word chemical equataion
The lime cycle
The manifacture and setting of lime is defined in three seperate processes.
Burning- When burning the calciun carbonate the carobon dioxide is driven of at teperatures of about 800 degrees centigrade to produce lump lime of calcium oxide.
Equation: Limestone+Heat--> Quicklime+Carbon Dioxide As a symbol equation this is CaCO3-->CaO+Co2
Slaking: Slaking of calcium hydroxide by the exothermic reaction with water to produce lime putty or calcium hydroxide. Word equation for this is: Quicklime+Water-->Slaked lime
Setting: of carbonation of cacium hydroxide by a slow reaction with carbon dioxide into the air to produce calcium carbonate. Word equation for this: Calcium Hydroxide+Carbon dioxide--> Calcium carbonate
Alternative names for quicklime and slaked lime:
Quicklime=Calcium Oxide Slaked Lime= Calcium hydroxide
Uses of Slaked lime and Mortar
Slaked limes is used to make motar. It is mixed with sand and water to help use it on bricks to hold them together. It is an ingredient in whitewash, motar and plaster.
Uses of mortar:
Lime mortar is used as an alternative to ordinary portland cement. It is made principally of lime (hydraulic, or non hydraulic), water and an aggregate such as sand.
Metal reactivity series
Other metals may be more reactive than other metals such as magnesium or in between magnesium and platanium. If we put the metals in order of reactivity, from the most reactive to the least reactive, we get a list called the reactivity series.
The reactivity for some common metals.
Extraction iron from iron oxide using the blast fu
Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite contain iron oxide. The oxygen must be removed from the iron oxide to leave iron behind. Reactions in which oxygen is removed is called reduction reactions.
Carbon is more reactive from iron, so it can push out or displace the iron from iron oxide. Here are the equations for the reactions.
Iron oxide+carbon-->Iron+carbon dioxide
2Fe2O3+3C-->4Fe+3CO2. In this reaction io=ron oxide is reduced to iron, and the carbon is oxidised to carbon dioxide.
In a blast furnace, it is so hot that carbon monoxide can be used to reduce the iron oxide in place of carbon.
Iron oxide+carbon monoxide-->Iron+ Carbon dioxide
Proporties of iron and steel
The physical properties of steel do not resemble its component element carbon and iron. It is high in strengh, low in weight, durable, flexible and corrosive resitant. It is highly fleible, hence it can be molded into any desired shape. One of the most important properties of steel is the ability to cool down quickly from a high temperature when exposed to water or oil. Unlike iron steel does not rust very easily on exposure to water or moisture.
Pure iron is unaffected by dry air and pure water at an ordianary temperature, but commecial iron rusts in moist air and water. Pure iron give off hydrogen, nitrogen, carbon monoxide on heating. The metal burn brilliantly when heated in oxygen and also undergos combustion in burning sulfur. It decomposes steam at red heat, which utilized the manifacture of hydrogen.
Common alloy's, uses and properties
Uses of Alliminium alloy's: Aliminium when combinded with other metals gives stength and charecteristics for a particular use. Aliminium alloy's are exstentivly used in production automotive engine parts . The huge array of quality aliminium is used in various applications like transport, packaging, electrical application, medicine, and constructions of homes and furniture.
Uses of copper alloy's: Copper alloys have excellent electrical and thermal performance, good corrosive resistance, high ductility, and relilativly low cost. Copper alloys are less exspensive than gold or platanium that is why largly utilized ondontilogical restorations. Due to its high strength, electrical and thermal conductivity copper alloys are used in the manifacture of all types of electrical equipment.
SMA (smart memory alloys)
Shape memory alloys are metals that after being strained, at a certain temperature revert back to their original shape. A change in their crystle structure above their transformation causes them to turn back to their original shape.
SMA's enable lare forces (generated when encoutering any resistance during their transformation) and large movement acutation. as they can recover large strains.
Extraction of copper, melting, uses of copper
Copper is less reactive than carbon, so it can be extracted from its ores by heating it with carbon. For example, copper is formed if copper oxide is heated strongly with charcoal - which is mostly carbon:
copper oxide + carbon → copper + carbon dioxide
Copper is purified by electrolysis. Electricity is passed through solutions containing copper compounds, such as copper sulphate. The anode - positive electrode - is impure copper. Pure copper forms on the cathode - negative electrode.
Uses of copper: Copper is used to pipe water supplies. The metal is also used in refrigerators and air conditioning systems. Computer heat sinks are made out of copper as it is able to absord a high amount of heat. As a good conductor of heat copper is used in copper wire, electromagnets, electrical relays and switches.
Aliminium and titanium
Aluminium and titanium are two metals that are low in density. This means that they are light weight for their size. They also have a very thin layer of their oxides on the surface, which stops air and water getting into the metal, so aluminium and titanium resist corrosion. These propeties make the two metals very useful.
Aluminium is used for air-craft, trains, over head power cables,sauce pans and cooking foil.Titaniumis used for fighter air-craft, artificial hip joints and and pipes in nuclear power stations.
Unlike iron, aluminium and titanium cannot be extracted from their oxides by reduction with carbon: Aluminium is more reactive than carbon, so the reaction does not work. Titanium forms titanium carbide with carbon, which makes the metal brittle.
Fuels from crude oil, hydrocarbons
Crude oils contains many different compounds that boil at different temperatures. These burn under different conditions so it needs to be separated to make useful fuels. We can separate mixtures of liquids by distillation. simple ditillation of crude oil can produce liquids that boil within different temperature ranges.
Most of the compounds in crude oil are hydrocarbons. This means that theys contain carbon and hydrogen only. Many of these hydrocarbons are alkanes, with general formula CnH2n+2. Alkanes contain as many hydrogen atoms as possible in each molecule and so we call them saturated hydrocarbons.
Molecules can be represented by: a molecular formula that shows the number of each type of atom. A structual formula that shows how the atoms are bonded together.
How fractional distillation works
Fractional distilation differs from distilations only in that it separates a mixture into a number of different parts, called fractions. A tall column is fitted above the mixture, with several condensers coming off at different heights. The columnis hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with low boiling point condese at the top. Like distillation, fractionla distillation works because the substances in the mixture have diffrent boiling points.
Fractional distillation of crude oil:
Because they have different boiling points, the substances in crude oil can be separated using fractional distillation. The crude oil is evaporated and its vapours allowed to condense at different temperatures in the fractionating column. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms.
The main fractions include, refinary gas, gasoline (petrol),naphtha, kerosene, diesel oil, fuel oil, and a residue that contains bitumen.
General formula for alkanes and how to draw them
Alkanes are saturated hydrocarbons as they only have single covalent bonds. Examples of alkanes, are gases produced by fractional distillation.
Alkanes have the general formula of CnH2n+2, below is a table of the first four alkanes in increasing order of carbon atoms.
FormulaStructure Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10
Refining crude oil
Crude oil is amixture of many different chemicals, most of which are hydrocarbons. These are chain molecules of varying length that are made from hydrogen and carbon atoms only.
Crude oil is refined by the petrochemical industry. The hydrocarbons are separated into fractions of familular size. These fraction include fuels such as, petrol, diesel, lubricants, and raw materials for chemical synthesis.
Most of the fractions burned from crude oil are burned as fuels. Only a small percent of crude oil is used for chemical synthesis.
The main purpose of fuel is to store energy, which should be in a stable form and can be easily transported to the place of production. Almost all fuels are chemical fuels. The user employs this fuel to generate heat or perform mechanical work, such as powering an engine. It may also be used to generate electricity, which is then used for heating, lighting or electronics purposes.
Biofuels are also considered a renewable source. Although renewable energy is used mostly to generate electricity, it is often assumed that some form of renewable energy or at least it is used to create alternative fuels.
Fuels made from oil mixtures containing large hydrocarbon molecules are not effiicient. They do not flow easily and they are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand- this is where craking comes in.
Craking allows larger molecules to be broken down into more smaller, more usefulhydrocarbon molecules. Fraction containing large hydrocarbon molecules are vaporised and passed over a hot catalyst. This breaks chemical bonds in the molecules, and forms smalled hydrocarbon molecules.
Making polymers from alkenes
Polymers are very large molecules made from many small molecules that have joined together. The small molecules used to make polymers are called monomers. Lots of ethene molecules can join together in long chains to form poly(ethene), commonly called polythene. The reaction is called polymerisation, because the molecules simply add together and only the polymer is produced.
We can react other alkenes together in a simular way to form polymers such as poly(propene). Many of the plastics we use as bags, bottles, containers and toys are made from alkenes.
Monomers ---> Polymer
Ethene ---> Polyethene
New and useful polymers
We can design the properties of polymers by choosing different monomers and by changing the conditions used to make them. Polymers are widely used for food packaging to keep food in good condition. Some of these polymers are not biodegradable and cause problems with waste disposal.
The polymers used for drinks bottles are strong, flexible, lightweight, clear and non-porous. Polymers have been developed to coat fabrics that make them waterproof but able to let gases through (breathable). New polymers have been developed for medical use, including hydrogels which are also used in agriculture and food. Smart polymers can be used to control the release of drugs and shape memory polymers are used for stiching wounds.
Extraction vegetable oils
Some seeds, nuts and fruits are rich in vegetable oils. The oils can be extracted by pressing followed by removing water and other impurities. Some oils are extracted by distilling the plants with mixed water. This produces a mixture of oil and water from which the oil cant be separated.
The molecules in vegetable oils have hydrocarbon chains. Those with carbon-carbon double bonds are unsaturated. If there are several double bonds in each molecule, they are called polyunsaturated. Unsaturated oils will react with bromine or iodine. Bromine water is used as the test for an unsaturated compound.
Vegetable oils produce alot of energy when eaten or when we burn them as fuels.
Cooking with vegetable oils
The boiling points of vegetable oils are higher than water, So food is cooked at higher temperatures in oil. This means that it cookes faster. It also changes the flavour, colour and texture of the food. Some of the oil is absorbed and so the energy content of the food increases.
Unsaturated oils can be reacted with hyrogen so that some or all of the double carbon-carbon bonds become single bonds. This is an addition reaction called hydrogenation and is done at about 60 degrees using a nickel catalyst. Hydorgenation is used to increase the melting points of oils so they harden and become solid fats at room temp.
solid fats can be spread and can be used to make cakes, biscuits and pastries.
Hydrogenation of vegetable oils
Saturated vegetable fats are solid at room temperature, and have a higher melting point than unsaturated oils. This makes them suitable for making margarine, or for commercial use in the making of cakes and pastry. Unsaturated vegetable oils can be ‘hardened’ by reacting them with hydrogen, a reaction called hydrogenation.
During hydrogenation, vegetable oils are reacted with hydrogen gas at about 60ºC. A nickel catalyst is used to speed up the reaction. The double bonds are converted to single bonds in the reaction. In this way unsaturated fats can be made into saturated fats – they are hardened.
Emulsions: mayonsise and emulsion paints are emulsions
type of emulsionexampleminor componentmajor component water in oil butter water fat oil in water milk fat water
Emulsions are made from liquids that usually separate from eachother. They are made by vigorously shaking, stirring or beating the liquids together to form tiny droplets of the liquids. The droplets are so small that they remain suspended in each other and are slow to separate.
Emulsifiers help keep the droplets to stay suspended and stop the liquids from separating. They do this because different parts of their molecules are attracted to the different liquids.
Emulsions are opaque and usually thicker than the liquids they are made from. This improves their texture, apperance and ability to stick to solids. Milk, sauces, salad dressings and icecream are examples of emulsions
Food additives- chromatography and mass spectossto
Substances added to food to improve its apperance, flavour, texture and keeping qualities are called food additives. Additives may be natural products or synthetic chemicals. These are the six main types of additive: colours, preservativs, antioxidants, emulsifiers, acidity regulators, flavourings.
Foods are checked by chemical analysis to ensure only permitted additives have been used. The methods used include chromatography and mass spectrometry.
Structure of the earth
The Earth is almostspherical with a radius of about 6400km. At the surface is a thin, solid crust. The thickness of the crust varies between 5km and 70km. It is thinnest under the oceans. The mantle is under the crust. It is about 3000km thick, and so goes almost halfway to the center of the earth. The mantle is almost entirely solid, but it can flow very slowly.
The core is very dense and made of metals, mainly nickel and iron. The outer core is liquid and the inner core is solid. This modelof the earth was built up using evidence from seismic waves from earthquakes. Scientists once thought that mountains and valleys were formed by the earth shrinking. They beleived that the crust solidfied as the earth cooled down and then the earth continued to shrink causing the crust to wrinkle.
Scientists now beleive that mountains form at boundaries between tectonic plates. Tectonic plates are large parts of the lithosphere, the earths crust and upper part of the mantle. The lithosphere is broken into tectonic plates that move a few centimeters a year.
Gas in the atmosphere
For the last 200 years the propotions of the gases in the atmosphere have been about the same as they are now The atomosphere is almost four-fifths nitrogen and just over one-fifth oxygen. The other gases make up about 1% of the atomsphere. They are noble gases (mainly argon), carbon dioxide (0.04%) and water vapour.
Most of the carbon dioxide in the early atmosphere ended up in the sedimentry rocks or fossil fuels. The noble gases are in group 0 of the periodic table. They are the least reactive elements and they are used where a lack of reactivity is important.
Argon is used as an inert atmosphere, for example in light bulbs to prevent the filament from buring.
Neon is used in electrical discharge tubes for advertising.
Helium is used in baloons.
The carbon cycle
Carbon dioxide moves into and out of the atmosphere and natural processes have kept this in balance for millions of years.
Plants remove carbon dioxide from the air for phtosynthesis to produce food. Carbon dioxide is released back into the atmosphere when plants and animals respire or decompose. Some of the carbon is used to make animal shells, and in the past these formed sedimentry rocks. Volcanoes produce carbon dioxide by decomposing carbonate rocks that have moved deep into the ground. Carbon in plants and animals also went into fossil fuels . When we burn fossil fuels we release carbon dioxide that had been absorbed from the atmosphere millions of years ago. Combustion of fossil fuels has incread very rapidly in the last 50 years and the levelof carbon dioxide in the atmosphere is increasing. As the amount of carbon dioxide increases more of it dissolves in the oceans.