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carbon st00ph
chemistry
| Question | Answer |
|---|---|
| fossil fuels | a natural fuel such as coal or gas, formed in the geological past from the heated and pressurized remains of living organisms - coal, oil, natural gas |
| where is crude oil found? | Crude oil is found trapped in some of the sedimentary rocks of the Earth's crust. |
| how is crude oil (and gas) formed? 1 | Millions of years ago, huge numbers of microscopic animals and plants - plankton - died and fell to the bottom of the sea. Their remains were covered by mud. |
| how is crude oil (and gas) formed? 2 | As the mud sediment was buried by more sediment, it started to change into rock as the temperature and pressure increased. The plant and animal remains were ‘cooked’ by this process, and slowly changed into crude oil. |
| how is crude oil (and gas) formed? 3 | Oil is less dense than the water in the rocks and will rise as a result of pressure from below (as can be seen in the animation above). often the oil will escape altogether if the rocks are permeable (liquids can pass through them). |
| how is crude oil (and gas) formed? 4 | If some of the rocks above the oil are impermeable the oil cannot rise through them, so it gets trapped underneath. Sometimes the oil gets trapped in the top of a fold underneath the solid layer of rock. Oil companies drill thru the rock to get to oil. |
| how is coal formed? | formed from dead plant material |
| why are fossil fuels non renewable? | They took a very long time to form and we are using them up faster than they can be renewed. Fossil fuels are also finite resources. They are no longer being made or are being made extremely slowly. 1ce they have all been used up, they cannot be replaced. |
| what is crude oil made of chemically? | a mixture of hydrocarbons (mainly alkanes) |
| what are hydrocarbons made of? | hydrogen and carbon molecules joined together by chemical bonds. Hydrocarbons are a group of compounds which contain the elements hydrogen and carbon. |
| different types of hydrocarbons | alkanes CnH2n+2 and alkenes CnH2n |
| small hydrocarbon properties | low boiling pt, very volatile, non-viscous (flows easily), ignites easily, pale, liquids/gases, weaker inter-molecular forces of attraction |
| large hydrocarbon properties | high boiling pt, not very volatile, viscous liquids (doesn't flow easily) or waxy solids, does not ignite easily, denser, stronger inter-molecular forces of attraction |
| how can geologists often tell where oil is trapped? | by looking at the structure of the rocks. Oil tends to be trapped where rocks are domed upwards, or where permeable rocks are in contact with impermeable rocks at a fault line. |
| what are the additional reserves of oil in rocks called? | oil shale |
| why is it expensive to extract oil from oil shale? | because it needs to be heated to release it |
| environmental problems with crude oil | oil spills cause oil slicks to travel across the sea, far from the original spill which damages beaches and wildlife and marine life as they are harmed when they are coated with oil. oil damages feathers and birds, sea otters, whales may get poisoned. |
| what is often used to clean oil slicks and why is it not good enough | detergent, these in turn may harm wildlife |
| how do oil companies drill for oil? | Oil companies can drill down through the impermeable rocks to get it out. production well is cut through to oil, oil drawn to surface. |
| political problems with oil | countries can argue and begin wars over who owns the oil. |
| what is distillation used for? when does it work? | to separate a pure liquid from a mixture of liquids. when the liquids have diff boiling pts. |
| explain what happens in distillation. 1 | The mixture is heated in a flask. Ethanol has a lower boiling point than water so it evaporates first. The ethanol vapour is then cooled and condensed inside the condenser to form a pure liquid. |
| explain what happens in distillation. 2 | The thermometer shows the boiling point of the pure ethanol liquid. When all the ethanol has evaporated from the solution, the temperature rises and the water evaporates. sequence of events in distillation: heating→evaporating→cooling→condensing |
| name the process by which crude oil is separated into more useful products? | fractional distillation |
| hydrocarbons between # and # carbon atoms are usually liquids | 5 and 12 |
| which hydrocarbons are usually gases | small hydrocarbons with only a few carbon atoms and have low boiling pts (<5) |
| which hydrocarbons are usually solids | large hydrocarbons with many carbon atoms and have high boiling pts |
| why can crude oil be separated by fractional distillation? | because it is a mixture of different hydrocarbons with different boiling points. |
| where does frac distillation of crude oil occur? where is it hot and where is it cool? | in a fractionating tower/column with several condensers coming off at different heights, hot (350c) at bottom, cool (25c) at top |
| explain how fractional distillation of crude oil works. | heated, vaporised crude oil enters at bottom, as it passes up it cools, fractions with high bpts condense + are collected at bottom, fractions with low bpts condense + are collected at top. Each frac has hc molecules with a similar number of carbon atoms. |
| from bottom (biggest) to top (smallest), name the products of fractional distillation of crude oil | residue (bitumen for roads and roof), fuel oil (for ships, power stations), heating oil (central heating), diesel oil (cars, lorries, buses), kerosene (aircraft fuel), naphtha (making chemicals), petrol fuel for cars), LPG/refinery gases (bottled gases) |
| why are smaller hc molecules in higher demand? | fuels made fromfrom oil mixtures containing large hc molecules aren't efficient. They are viscous and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules, and not enough small hydrocarbon molecules, to meet demand. |
| how are larger hc molecules made into smaller hc molecules? | oil companies can break down large molecules into more useful smaller alkane and alkene molecules, cracking. |
| what is cracking? | cracking is a thermal decomposition reaction and requires heat and a catalyst. cracking also splits up large alkane molecules into smaller alkane molecules and an alkene molecule which can be used to make polymers/plastics. |
| what happens in cracking? | heat long hc to vaporise it. pass over a powdered catalyst (Al2O3, 400-700c). long hc split apart on surface of the specks of catalyst. |
| products of cracking | shorter hcs which are more useful as fuels such as petrols. shorter alkanes. alkenes which are useful because they are used to make polymers |
| why are larger hcs having higher bpts? | intermolecular forces of attraction between large molecules > than between small molecules. thus, more energy is needed to break the forces of attraction between large molecules and so the boiling point is higher. |
| Factors influencing the use of a fuel | energy value of the fuel in kJ/g of fuel. availability. how it can be stored, cost, toxicity (is it poisonous), pollution caused, ease of use. |
| energy value of natural gas, petrol, coal. mg of carbon dioxide produced for each kJ. | 52,43,24 ..... 53,71,93 |
| how are fuels used? | they react with oxygen to release energy. most of the energy is released as heat, but light energy is also released. |
| complete combustion | combustion reaction that needs a plentiful supply of air/oxygen so that the elements in the fuel can react fully with oxygen. produces carbon dioxide and water. carbon oxidises to water, hydrogen oxidises to water. |
| complete combustion equation | hydrocarbon + oxygen → carbon dioxide + water |
| incomplete combustion | occurs when the supply of air or oxygen is poor. hydrogen still oxidises to water, but carbon is not fully oxidised - carbon monoxide and carbon (soot) are produced instead of carbon dioxide. |
| incomplete combustion equation | hydrocarbon + oxygen → carbon monoxide + carbon + water |
| problem with carbon monoxide | poisonous, odorless, colorless gas so kills with very little warning. reacts with haemoglobin in your blood and stops it from carrying oxygen to the body cells. |
| problem with soot | particle size of soot so small, can get deep into your lungs when breathed, can cause lung cancer. can damage trees and plants and make buildings black and grimy. global dimming |
| bunsen burner fuel | methane ch4 |
| whats the point of the air hole in bunsen burner | it allows complete or incomplete combustion |
| air hole open | air is drawn into the chimney where it mixes with natural gas, ensures complete combustion. very hot, blue flame is produced |
| air hole closed | natural gas can only mix with air at the mouth of the chimney. Incomplete combustion occurs as a result. yellow flame produced, which transfers less heat energy than blue flame. brighter than blue flame because specks of carbon glow when heated. |
| proportion of main gases in atmosphere | nitrogen 78%, oxygen 21%, argon 0.9%, carbon dioxide 0.035%. other, water vapour |
| early atmosphere | created from gases escaping Earth's interior and given out by volcanoes - there was intense volcanic activity for the 1st billion years of Earth's existence. mostly CO2 and H2O, little or no O2, small proportions of ammonia, methane. |
| evolution of atmosphere - water | proportions went down because, as Earth cooled down, most of the water vapour condensed and formed oceans. |
| evolution of atmosphere - CO2 | proportion went down - absorbed by plants for photosynthesis, locked up in fossil fuels, dissolved in the oceans. |
| evolution of atmosphere - ammonia | proportion went down because it reacted with oxygen to produce nitrogen |
| evolution of atmosphere - nitrogen | proportion went up because it was released by the reaction between ammonia and oxygen. nitrogen is not very reactive and once formed, it is not easily removed from the atmosphere again. |
| evolution of atmosphere - oxygen | proportion went up because of photosynthesis by plants |
| carbon cycle | photosynthesis removes co2 from atmosphere, respiration, combustion release co2 into atmosphere. these processes form a carbon cycle in which the proportion of carbon dioxide in the atmosphere remains about the same. |
| The use of fossil fuels, for example in vehicle engines and power stations, causes air pollution. what are the common air pollutants? | carbon monoxide, oxides of nitrogen, NOx, sulfur dioxide. |
| how is carbon monoxide formed? | incomplete combustion of the fuel in car engines |
| how are oxides of nitrogen, NOx formed? | formed from the heat and pressures found in a car engine |
| how is sulfur dioxide formed? | sulfur impurities in the fuel burn |
| problem with oxides of nitrogen, NOx | react with other pollutants in sunlight to form a photochemical smog, which causes breathing difficulties. forms acid rain |
| problems with sulfur dioxide | forms acid rain. sulfur can be removed from fuels before they are burned but takes more energy which usually comes from burning more fuel (releasing co2) and costs more to do it. petrol and diesel are starting to use low-diesel versions. |
| problem with acid rain | has several effects on the environment, including: killing plants and aquatic life, eroding stonework, corroding metals |
| function of catalytic converters | to convert harmful gases (CO, NOx) into less harmful gases (CO2, N2) |
| how does catalytic converters work | CO and NO absorbed onto a metal surface and temporary bonds are formed between the catalytic surface and the harmful gases. NO and CO react with each other forming CO2 and N2. the products are desorbed and diffuse away from the cat surfaces |
| where are catalytic converters found? | car exhaust systems |
| word equation for catalytic converter | carbon monoxide + nitrogen oxide → nitrogen + carbon dioxide |
| symbol equation for catalytic converter | 2CO + 2NO -> 2CO2 + 2N2 |
| other equations for catalytic converters | 2CO + O2 -> 2CO2 2NOx -> xO2 + N2 unburnt hydrocarbons -> carbon dioxide + water |
| what are the bonds that join the carbon and hydrogen atoms in a hydrocarbon | covalent |
| alkanes | saturated hydrocarbons, |
| what does saturated hydrocarbons mean | their carbon atoms are joined to each other by single covalent bonds. |
| alkenes | unsaturated hydrocarbons that contain a carbon-carbon- double bond. The presence of this double bond allows alkenes to react in ways that alkanes cannot. |
| how to test for alkene | Bromine water is an orange solution of bromine. It becomes colourless when shaken with an alkene. Alkenes can decolourise bromine water, while alkanes cannot. |
| reaction between bromine and alkenes is an example of a type of reaction called an | addition reaction. the bromine is decolourised because a colourless dibromo compound forms for example: ethene + bromine → dibromoethane |
| polymers | large molecules formed from many identical smaller molecules (monomers (simple molecule)) - plastics |
| why are alkenes used in polymerisation | because they can act as monomers because they contain a double bond. They can join end-to-end in a reaction called addition polymerisation. The polymers they form are called addition polymers. monomer is unsaturated, but the polymer is saturated. |
| general polymerisation | a lot of monomes -> a polymer molecule |
| drawing displayed formulas of polymers | n(monomer) -polymerisation-> (repeating unit)n. change the double bond in the monomer to a single bond in the repeating unit. add a bond to each end of the repeating unit. |
| how can ethene be made into ethanol | ethene react with steam. temp of 300c and pressure of 70 atmospheres. phospohoric acid used as a catalyst. atm its a cheap process because ethene is fairly cheap and not much is wasted. but its made from crude oil (nonrenewable) will get expensive soon. |
| high pressure, high temps polymers properties | flexible, low density, weak, lower usable temperature, many branches on polymer molecules |
| low pressure, low temps polymers properties | rigid, high density, strong, higher usable temperature, few branches on polymer molecules |
| condensation polymers | polymers not made from alkene monomers. e.g. nylon, polyesters. They can be drawn into very fine fibres and woven into cloth for clothing. Often, natural fibres such as cotton are mixed with nylon or polyester fibres to make a soft but hard-wearing cloth. |
| nylon desirable properties | does not let UV light pass through, tough, lightweight, waterproof. |
| problem with nylon | Unfortunately, nylon does not let water vapour pass through it either. This means nylon waterproof clothing traps sweat, so that after a while the inside of the clothing becomes wet and unpleasant to wear. |
| gore-tex | Gore-Tex has the desirable properties of nylon, but is also 'breathable'. It lets water vapour from sweat pass to the outside, but it stops rain drops from passing to the inside. |
| to whom is gore-tex useful | Clothing made of Gore-Tex is very useful to hikers and other people who work or play outside. |
| construction of gore-tex 1 | Gore-Tex contains layers of nylon, PTFE and polyurethane. PTFE contains lots pores - there are around 14 million per square millimetre. Each one is too small for water droplets to pass through, but big enough to let water molecules from sweat out. |
| construction of gore-tex 2 | Without the nylon, the layers would be too fragile to be useful. sandwich of materials - tough outer layer > protective layer > gore-tex membrane > protective layer > soft lining |
| PTFE properties | very slippery, used to make non-stick coatings for pans. |
| polymers are unreactive so can be suitable for... | storing food and chemicals safely |
| why is this property also bad | this property makes them not biodegradable - microbes cannot digest them and they take a long time to break down. its difficult to dispose of polymers. They are often buried in landfill sites or incinerated - burned. |
| ways polymers are disposed of | landfill, incineration, recycling |
| landfill | Waste polymers are disposed of in landfill sites. This uses up valuable land, and suitable sites often fill up quickly. |
| incineration | Polymers release a lot of heat energy when they burn. energy can be used to heat homes or generate electricity. problems with incineration. CO2 is produced, adds to global warming. Toxic gases are also produced, unless the polymers are burned at hi temp |
| recycling | Many polymers can be recycled. This reduces disposal problems and the amount of crude oil used. But first the different polymers must be separated from each other. This can be difficult and expensive. |
| new types of polymers | it is possible to include chemicals that cause the polymer to break down more quickly. Carrier bags and refuse bags made from degradable polymers are already available. |
| water-soluble polymers | Some polymers are water-soluble, which means they dissolve in water. These polymers are often used to wrap products such as dishwasher tablets and pouches containing detergent for washing machines. |
| the properties of solids like polymers depend on | how their molecules are arranged the strength of the forces between these molecules. |
| when will a polymer melt | A polymer will melt when the intermolecular forces are overcome. The stronger the forces, the more energy is needed to break them, and the higher the material’s melting point. |
| how are the forces of attraction in polymers | Strong covalent bonds join atoms to each other in individual polymer molecules. Weak intermolecular forces attract polymer molecules towards each other. |
| polymer chains | Many polymers contain long molecules that lie side by side. These can uncoil and slide past each other, making the material flexible. Long polymer chains have stronger forces of attraction than shorter ones: they make stronger materials |
| cross-linking | the polymer chains are chemically joined together in places, by covalent bonds. The polymer molecules cannot slide over each other so easily. This makes materials tougher and less flexible, and they cannot be easily stretched. give materials high melt pt |
| example of material that uses cross-linking | Vulcanised rubber has cross-links. Its polymer molecules are cross-linked by sulfur atoms. It is tough but flexible, and used for making tyres. |
| alternative fuels | ethanol (fermentation of plants), biogas (mixture of methane and co2, produced when microbes digest waste material) hydrogen gas (electrolysis of water) |
| ethanol pros | co2 released when burnt was taken in by the plant as it grew so its carbon neutral. only other product is water |
| ethanol cons | engines need to be converted before theyll work with ethanol fuels. ethanol fuel isnt widely available |
| biogas pros | waste material is readily available and cheap. carbon neutral |
| biogas cons | biogas production is slow in cool weather |
| hydrogen gas pros | hydrogen combines with oxygen in the air to form just water - so its very clean |
| hydrogen gas cons | you need a special, expensive engine and hydrogen isnt widely available. you still need to use energy from another source to make it. also hydrogen is hard to store |
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karspider
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