Chemistry 1a

Flashcards by lauramarypowell, updated more than 1 year ago
Created by lauramarypowell about 6 years ago


AQA chemistry 1a GCP revision guide

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What is a nucleus? 1) It's in the middle of the atom. 2) It contains protons and neutrons. 3) Protons are positively charged. 4) Neutrons have no charge (they're neutral). 5) So the nucleus has a positive charge overall because of the protons. 6) But size-wise it's tiny compared to the rest of the atom.
What are the electrons? 1) Move around the nucleus. 2) They're negatively charged. 3) They're tiny, but they cover a lot of space. 4) They occupy shells around the nucleus. 5) These shells explain the whole of Chemistry.
What is in an atom? Atoms have a small nucleus surrounded by electrons.
How do atoms stay neutral, become negative or positive? 1) Atoms have no charge. They are neutral. 2) The charge on the elections is the same size as the charge on the protons - but opposite. 3) This means the number of protons always equals the number of electrons in an atom. 4) If some electrons are added or removed, the atom becomes charged and is then an ion.
What decides what type of atom an atom will be? 1) Atoms can have different numbers of protons, neutrons and electrons. It's the number of protons in the nucleus that decides what type of atom it is. 2) For example, an atom with one proton in its nucleus is hydrogen and an atom with two protons is helium.
What is an element? 1) If a substance only contains one type of atom it's called an element. 2) There are about 100 different elements - quite a lot of everyday substances are elements:- copper, aluminium, iron, oxygen and nitrogen. 3) So all the atoms of a particular element (e.g.nitrogen) have the same number of protons and different elements have atoms with different numbers of protons.
How can atoms be represented by symbols and what does: C, O, Mg, Na, Fe and Pb? Atoms of each element can be represented by a one or two letter symbol - it's a type of shorthand that saves you the bother of having to write the full name of the element. Some make perfect sense : e.g. C=carbon, O=oxygen, Mg=magnesium. Others seem to make as much sense as an apple with a handle. e.g. Na=sodium, Fe=iron and Pb=lead.
How does the periodic table put elects with similar properties together? Use group 1and 0 as examples. 1) The periodic table is laid out so that elements with similar properties form columns. 2) These vertical columns are called groups and Roman numerals are often used for them. 3) All of the elements in a group have the same number of electrons in their outer shell. 4) This is why elements in the same group have similar properties. So, if you know the properties of one element you can predict properties of other elements in that group. 5) For example, the group 1 elements are Li, Na, K, Rb, Cs and Fr. They're all metals and they react the same way. E.g. they all react with water to form an alkaline solution and hydrogen gas, and they all react with oxygen to form an oxide. 6) The elements in the final column (Group 0) are the noble gases. They all have 8 electrons in their outer shell, apart from helium which has 2. This means that they're stable and unreactive.
What does the top and bottom numbers show? 1) The top number is the mass number. This is the total number of protons and neutrons. 2) The bottom number is the atomic number. This is the number of protons, which conveniently also tells you the number of electrons. 3) So if you want to find the number of neutrons in an atom, just subtract the atomic number from the mass number.
What are the electron shell rules? 1) Electrons always occupy shells (sometimes called energy levels). 2) The lowest energy levels are always filled first - these are the ones closest to the nucleus. 3) Only a certain number of electrons are allowed in each shell: 1st shell: 2, 2nd shell: 8 and 3rd shell: 8. 4) Atoms are much happier when they have full electron shells - like the noble gases in group 0. 5) In most atoms the outer shell is not full and this make the atom want to react to fill it.
What are the rules to work out electronic structure? (use nitrogen as an example). You need to know the electronic structure for the first 20 elements. But they're not hard to work out. For a quick example, take nitrogen. Follow the steps ……. 1) The periodic table tells us nitrogen has seven protons….. so it must have seven electrons. 2) Follow the 'Electron Shell Rules'. The first shell can only take 2 electrons and the second shell can take a maximum of 8 electrons. 3) So the electronic structure for nitrogen must be 2,5.
How do you calculate the electronic structure of argon? 1) To calculate the electronic structure of argon, follow the rules. It's got 18 protons so it must have 18 electrons. The first shell must have 2 electrons, the second shell must have 8, and so the third shell must have 8 as well. It as easy as 2,8,8.
How do atoms join together to make compounds? 1) When different elements react, atoms form chemical bonds with other atoms to form compounds. It's usually difficult to separate the two original elements out again. 2) Making bonds involves atoms giving away, taking or sharing electrons. Only the electrons are involved. 3) A compound which is formed from a metal and a non-metal consists of ions. The metal atoms lose electrons to form positive ions and the non-metal atoms gain electrons to form negative ions. The opposite charges (positive and negative) of the ions mean that they're strongly attracted to each other. This is called ionic bonding. E.g. a sodium atom gives an electron to a chlorine atom. 4) A compound formed from non-metals consists of molecules. Each atom shares an electron with another atom - this is called a covalent bond. Each atom has to make enough covalent bonds to fill up its outer shell. E.g. HCl a hydrogen atoms bonds with a chlorine atom by sharing an electron with it.
How are the properties of compound different from the original elements? Use iron sulfide as an example. 1) The properties of a compound are totally different from the properties of the original elements. For example, if iron (a lustrous magnetic metal) and sulfur (a nice yellow powder) react, the compound formed (iron sulfide) is a dull grey solid lump, and doesn't behave anything like either iron or sulfur. The mixture of iron and sulfur + heat gives the compound iron sulfide. 2) Compound can be small molecules like water, or great whopping lattices like sodium chloride.
How can a formula show what atoms are in the compound? Use carbon dioxide, sulfuric acid and calcium hydroxide as examples. 1) Carbon dioxide, CO2, is a compound formed from a chemical reaction between carbon and oxygen. It contains 1 carbon atom and 2 oxygen atoms. 2) Here's another example: the formula of sulfuric acid is H2SO4. So, each molecule contains 2 hydrogen atoms, 1 sulfur atom and 4 oxygen atoms. 3) There might be brackets in the formula, e.g. calcium hydroxide is Ca(OH)2. The little number outside the bracket applies to everything inside the brackets. So in Ca(OH)2 there is 1 calcium atom, 2 oxygen atoms and 2 hydrogen atoms.
What happens to atoms in chemical reactions? 1) During chemical reactions, things don't appear out of nowhere and things don't just disappear. 2) You still have the same atoms at the end of a chemical reaction as you had at the start. They're just arranged in different ways. 3) Balanced symbol equations show the atoms at the start (the reactant atoms) and the atoms at the end (the product atoms) and how they're arranged e.g.: word equation: magnesium +oxygen = magnesium oxide. Balanced symbol equation: 2Mg + O2 = 2MgO. 4) Because atoms aren't gained or lost, the mass of the reactants equals the mass of the products. So if you completely react 6g of magnesium with 4g of oxygen, you'd end up with 10g of magnesium oxide.
How do you balance equations and what is wrong with this equation: H2SO4 +NaOH = Na2SO4 + H2O. 1) There must always be the same number of atoms of each element on both sides - they can't just disappear. 2) You balance the equation by putting numbers in front of the formulas where needed. Take this equation for reacting sulfuric acid (H2SO4) with sodium hydroxide (NaOH) to get sodium sulfate (Na2SO4) and water (H2O): H2SO4 + NaOH = Na2SO4 +H2O. The formulas are all correct but the numbers of some atoms don't match up on both sides. E.g. there are 3 Hs on the left, but only 2 on the right and 1 Na on the left and 2 on the right.
How do you balance an equation? 1) Find an element that doesn't balance and pencil in a number to try and sort it out. 2) See where it gets you. It may create another imbalance - if so, just pencil in another number and see where that gets you. 3) Carry on chasing unbalanced elements and it'll sort itself out.
Balance the equation: H2SO4 + NaOH = Na2SO4 +H2O. We need to sort out the imbalance of H atoms and Na atoms. 1) The only thing you can do about that is make it 2H2O instead of just H2O: H2SO4 + NaOH = Na2SO4 + 2H2O. 2) But that now causes too many H atoms and O atoms on the right hand side, so to balance that up you could try putting 2NaOH on the left hand side: H2SO4 + 2NaOH = Na2SO4 + 2H2O. 3) And suddenly there it is! Everything balances. And you'll notice the Na just sorted itself out.
Why is limestone quarried? Limestone's quarried out of the ground - it's great for making into blocks for building with. Fine old buildings like cathedrals are often made purely from limestone blocks. It's pretty sturdy stuff, but don't go thinking it doesn't react with anything.
What is limestone? 1) Limestone is mainly calcium carbonate - CaCO3.
What happens to limestone when it is heated? When it's heated it thermally decomposes to make calcium oxide and carbon dioxide. CaCO3 (s) = CaO (s) + CO2 (g). a) When magnesium, copper, zinc and sodium carbonates are heated, they decompose in the same way. E.g. magnesium carbonate = magnesium oxide + carbon dioxide. b) However, you might have difficulty doing some of these reactions in class - a bunsen burner can't reach a high enough temperature to thermally decompose some carbonates of group 1 metals.
What is thermal decomposition? Thermal decomposition is when one substance chemically changes into at least two new substances when it's heated.
How does calcium carbonate (limestone) react with acid? Calcium carbonate also reacts with acid to make a calcium salt, carbon dioxide and water. E.g:Calcium carbonate + sulfuric acid = calcium sulfate + carbon dioxide +water CaCO3 + H2SO4 = CaSO4 + CO2 + H2O. a) The type of salt produced depends on the type of acid. For example, a reaction with hydrochloric acid would make a chloride (e.g. CaCl2). b) Other carbonates that react with acids are magnesium, copper, zinc and sodium. c) This reaction means that limestone is damaged by acid rain.
How does calcium oxide react with water? 1) When you add water to calcium oxide you get calcium hydroxide. Calcium oxide + water = calcium hydroxide or CaO + H2O = Ca(OH)2.
How can calcium hydroxide be used? 1) Calcium hydroxide is an alkali which can be used to neutralise acidic soil in fields. Powdered limestone can be used for this too, but the advantage of calcium hydroxide is that it works much faster. 2) Calcium hydroxide can also be used in a test for carbon dioxide. If you make a solution of calcium hydroxide in water (called limewater) and bubble gas through it, the solution will turn cloudy if there's carbon dioxide in the gas. The cloudiness is caused by the formation of calcium carbonate. Calcium hydroxide +carbon dioxide = calcium carbonate + water. Ca(OH)2 + CO2 = CaCO3 + H2O.
What is limestone used to make? 1) Powdered limestone is heated in a kiln with powdered clay to make cement. 2) Cement can be mixed with sand and water to make mortar. Mortar is the stuff you stick bricks together with. You can add calcium hydroxide to mortar. 3) Or you can mix cement with sand and aggregate (water and gravel) to make concrete.
How does quarrying limestone make a mess of the landscape? Digging limestone out of the ground can cause environmental problems. 1) For a start, it makes huge ugly holes which permanently change the landscape. 2) Quarrying processes, like blasting rocks apart with explosives, make lots of noise and dust in quiet, scenic areas. 3) Quarrying destroys the habitats of animals and birds. 4) The limestone need to be transported away from the quarry - usually in lorries. This causes more noise and pollution. 5) Waste materials produce unsightly tips.
How does making stuff from limestone cause pollution? 1) Cement factories make a lot of dust, which can cause breathing problems for some people. 2) Energy is needed to produce cement and quicklime. The energy is likely to come from burning fossil fuels, which causes pollution.
What are the plus sides of quarrying for limestone? 1) Limestone provides things that people want - like houses and roads. Chemicals used in making dyes, paints and medicines also come from limestone. 2) Limestone products are used to neutralise acidic soil. Acidity in lakes and rivers caused by acid rain is also neutralised by limestone products. 3) Limestone is also used in power station chimneys to neutralise sulfur dioxide, which is the cause of acid rain. 4) The quarry and associated businesses provide jobs for people and bring more money into the local economy. This can lead to local improvements in transport, roads, recreation facilities and health. 5) Once quarrying is complete, landscaping and restoration of the area is normally required as part of the planning permission.
What are the advantages and disadvantages of limestone products? Limestone and concrete (made from cement) are used as building materials. In some cases they're perfect for the job but in other cases they're a bit of a compromise. 1) Limestone is widely available and cheaper than granite or marble. It's also a fairly easy rock to cut. 2) Some limestone is more hard-wearing than marble, but it still looks attractive. 3) Concrete can be poured into moulds to make blocks or panels that can be joined together. It's a very quick and cheap way of constructing buildings and it shows - concrete is the most unattractive building material. 4) Limestone, concrete and cement don't rot when they get wet like wood does. They can't be gnawed away by insects or rodents either. And to top it off, they're fire resistant too. 5) Concrete doesn't corrode like lots of metals do. It does have a fairly low tensile strength though and can crack. If it's reinforced with steel bars it'll be much stronger.
What is a metal ore? A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it.
How is extraction of ores worthwhile? 1) In many cases the ore is an oxide of the metal. For example, the main aluminium ore is called bauxite - it's aluminium oxide (Al2O3). 2) Most metals need to be extracted from their ores using a chemical reaction. 4) The economies (profitability) of metal extraction can change over time. For example: a) If the market price of a metal drops a lot, it might not be worth extracting it. If the price increases a lot then it might be worth extracting more of it. b) As technology improves, it becomes possible to extract more metal from a sample of rock than was originally possible. So it might now be worth extracting metal that wasn't worth extracting in the past.
How are metals extracted from their ores? 1) A metal can be extracted from its ore chemically - by reduction or by electrolysis (splitting with electricity). 2) Some ores may have to be concentrated before the metal is extracted - this just involves getting rid of the unwanted rocky material. 3) Electrolysis can also be used to purify the extracted metal.
How can some metals be extracted using carbon? 1) A metal can be extracted from its ore chemically by reduction using carbon. 2) When an ore is reduced, oxygen is removed from it, e.g. 2Fe2O3 + 3C = 4Fe + 3CO2. Iron (III) oxide + carbon = iron + carbon dioxide. 3) The position of the metal in the reactivity series determines whether it can be extracted by reduction with carbon.
How does the position of the metal in the reactivity series determine whether you use electrolysis or reduction with carbon? a) Metals higher than carbon in the reactivity series (Al, Mg, Ca, Na and K) have to be extracted using electrolysis which is expensive. b) Metals below carbon in the reactivity series (Zn, Fe, Sn and Cu) can be extracted by reduction using carbon. For example, iron oxide is reduced in a blast furnace to make iron. c) Carbon can only take the oxygen away from metals which are less reactive than carbon itself that is why the position of metal in the reactivity series is important in determining the way the metal is extracted.
What metals have to be extracted by electrolysis? 1) Metals that are more reactive than carbon have to be extracted using electrolysis of molten compounds. 2) An example of a metal that has to be extracted this way is aluminium. 3) However, the process is much more expensive than reduction with carbon because it uses a lot of energy. 4) For example: a high temperature is needed to melt aluminium oxide so that aluminium can be extracted - this requires a lot of energy, which makes it an expensive process.
How is copper purified? 1) Copper can be easily extracted by reduction with carbon. The ore is heated in a furnace - this is called smelting. 2) However, the copper produced this way is impure - and impure copper doesn't conduct electricity very well. This isn't very useful because a lot of copper is used to make electrical wires. 3) So electrolysis is also used to purify it, even though it's quite expensive. 4) This produces very pure copper, which is a much better conductor.
What is electrolysis? 1) Electrolysis is the breaking down of a substance using electricity. 2) It requires a liquid to conduct the electricity, called the electrolyte. 3) Electrolytes are often metal salt solutions made from the ore (e.g. copper sulfate) to molten metal oxides. 4) The electrolyte has free ions - these conduct the electricity and allow the whole thing to work. 5) Electrons are taken away by the (positive) anode and given away by the (negative) cathode. As ions gain or lose electrons they become atoms or molecules and are released.
How is electrolysis used to get copper? 1) The electrolyte is copper (II) sulfate solution containing Cu2+ ions. 2) Electrons are pulled off copper atoms at the anode (the anode is just a big lump of impure copper which will dissolve), causing them to go into solution as Cu2+ ions. 2) Cu2+ ions near the cathode (the cathode starts as a thin piece of pure copper and more pure copper adds to it) gain electrons and turn back into copper atoms. 3) The impurities are dropped at the anode as a sludge whilst pure copper atoms bond to the cathode.
How can you extract copper from a solution using a displacement reaction? 1) More reactive metals react more vigorously than less reactive metals. 2) If you put a reactive metal into a solution of dissolved metal compound, the reactive metal will replace the less reactive metal in the compound. 3) This is because the more reactive metal bonds more strongly to the non-metal bit of the compound and pushes out the less reactive metal. 4) For example, scrap iron can be used to displace copper from solution - this is really useful because because iron is cheap but copper is expensive. If some iron is put in a solution of copper sulfate, the more reactive iron will 'kick out' the less reactive copper from the solution. You end up with iron sulfate solution and copper: copper sulfate+iron = iron sulfate + copper. 5) If a piece of silver metal is put into a solution of copper sulfate, nothing happens. The more reactive metal (copper) is already in the solution.
Why are copper-rich ores in short supply? 1) The supply of copper-rich ores is limited, so it's important to recycle as much copper as possible. 2) The demand for copper is growing and this may lead to shortages in the future. 3) Scientists are looking into new ways of extracting copper from low-grade ores (ores that only contain small amounts of copper) or from the waste that is currently produced when copper is extracted.
What are the new methods to extract copper? 1) Bioleaching: this uses bacteria to separate copper from sipper sulfide. The bacteria get energy from the bond between copper and sulfur, separating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted, e.g. by filtering. 2) Phytomining: this involves growing plants in soil that contains copper. The plants can't use or get rid of the copper so it gradually builds up in the leaves. The plants can be harvested, dried and burned in a furnace. The copper can be collected from the ash left in the furnace. 3) Traditional methods of copper mining are pretty damaging to the environment, these new methods of extraction have a much smaller impact, but the disadvantage is that they're slow.
How can metal extraction be bad for the environment? What are the positives and negatives of mining ores? 1) People have to balance the social, economic and environmental effects of mining the ores. 2) Most of the issues are exactly the same as those to do with quarrying limestone: - so mining metal ores is good because it means that useful products can be made. It also provides local people with jobs and brings money into the area. This means services such as transport and health can be improved. - But mining ores is bad for the environment as it causes noise, scarring of the landscape and loss of habitats. Deep mine shafts can also be dangerous for a long time after the mine has been abandoned.
Why is recycling metals important? 1) Mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels. 2) Fossil fuels are running out so it's important to conserve them. Not only this, but burning them contributes to acid rain, global dimming and climate change. 3) Recycling metals only uses a small fraction of the energy needed to mine and extract new metal. E.g. recycling copper only take 15% of the energy that's needed to mine and extract new copper. 4) Energy doesn't come cheap, so recycling saves money too. 5) Also, there's a finite amount of each metal in the earth. Recycling conserves theses resources. 6) Recycling metal cuts down on the amount of rubbish that gets sent to landfill. Landfill takes up space and pollutes the surrounding. If all the aluminium cans in the UK were recycled, there'd be 14 million fewer dustbins to empty each year.
What is the periodic table mostly filled with? 1) Most of the elements are metals - so they cover most of the periodic table. In fact, only the elements on the far right are non-metals.
What are the properties of all metals? 1) All metals have some fairly similar basic properties: a) Metals are strong (hard to break), but they can be bent or hammered into different shapes. b) They're great at conducting heat. c) They conduct electricity well.
Why do metals have everyday uses? 1) Metals (and especially transition metals, which are found in the centre block of the periodic table) have loads of everyday uses because of these properties: a) Their strength and 'bendability' makes them handy for making into things like bridges and car bodies. b) Metals are ideal if you want to make something that heat needs to travel through, like a saucepan base. c) And their conductivity makes them great for making things like electrical wires.
How does the properties of copper, aluminium and titanium decide how it's best used? 1) The typical properties of a metal are strong, malleable, good conductors of electricity and heat. Not all metals are the same though - you need to learn the specific properties of the following three metals: a) Copper is a good conductor of electricity, so it's ideal for drawing out into electrical wire. It's hard and strong but can be bent. It also doesn't react with water. b) Aluminium is corrosion-resistant and has a low density. Pure aluminium isn't particularly strong but it forms hard, strong alloys. c) Titanium is another low density metal. Unlike aluminium it's very strong. It is also corrosion - resistant.
Why are different metals chosen for different uses? (use copper, aluminium and titanium as examples). 1) Different metals are chosen for different uses because of their specific properties. For example: a) If you were doing some plumbing, you'd pick a metal that could be bent to make pipes and tanks, and is below hydrogen in the reactivity series so it doesn't react with water. Copper is great for this. b) If you wanted to make an aeroplane, you'd probably use a metal as it's strong and can be bent into shape. But you'd also need it to be light, so aluminium would be a good choice. c) And if you were making replacement hips, you'd pick a metal that won't corrode when it comes in contact with water. It'd also have to be light too, and not too bendy. Titanium has all of these properties so it's used for this.
Why are metals good, but not perfect? 1) Metals are very useful structural materials, but some corrode when exposed to air and water, so they need to be protected, e.g. by painting. If metals corrode, they lose their strength and hardness. 2) Metals can get 'tired' when stresses and strains are repeatedly put on them over time. This is known as metal fatigue and leads to metals breaking, which can be very dangerous, e.g. in plane.
Why is pure iron a bit bendy? 1) 'Iron' straight from the last furnace is only 96% iron. The other 4% is impurities such as carbon. 2) This impure iron is used as cast iron. It's handy for making ornamental railings, but it doesn't have many other uses because it's brittle. 3) So all the impurities are removed from most of the blast furnace iron. This pure iron has a regular arrangement of identical atoms. The layers of atoms can slide over each other, which makes the iron soft and easily shaped. This iron is far too bendy for most uses.
What are the properties and uses of different types of steel? Most of the pure iron is changed into alloys called steels. Steels are formed by adding small amounts of carbon and sometimes other metals to the iron. 1) Low carbon steel (0.1% carbon) which is easily shaped and can be used to make car bodies. 2) High carbon steel (1.5% carbon) which is very hard, inflexible can be used to make blades for cutting tools and bridges. 3) Stainless steel (chromium added and sometimes nickel) which is corrosion-resistant and can be used to make cutlery and containers for corrosive substances.
Why are alloys harder than pure metals? Name metals and their uses which are actually alloys. 1) Different elements have different sized atoms. So when an element such as carbon is added to pure iron, the smaller carbon atom will upset the layer of pure iron atoms, making it more difficult for them to slide over each other. So alloys are harder. 2) Many metals in use today are actually alloys e.g: a) Bronze = Copper + Tin, bronze is harder than copper. It's good for making medals and statues from. b) Cupronickel = Copper + Nickel, this is hard and corrosion resistant. It's used to make "silver" coins. c) Gold alloys are used to make jewellery, pure gold is too soft. Metals such as zinc, copper, silver, palladium and nickel are used to harden the "gold". d) Aluminium alloys are used to make aircrafts: Aluminium has a very low density, but it's alloyed with small amounts of other metals to make it stronger. 3) In the past, the development of alloys was by trial and error. But nowadays we understand much more about the properties of metals, so alloys can be designed for specific uses.
What is crude oil? 1) Crude oil is a mixture of hydrocarbons. 2) A mixture consists of two (or more) elements or compounds that aren't chemically bonded to each other. 3) Crude oil is a mixture of many different compounds. Most of the compounds are hydrocarbon molecules. 4) There are no chemical bonds between the different parts of a mixture, so the different hydrocarbon molecules in crude oil aren't chemically bonded to one another.
What are the properties of crude oil? How can crude oil be separated out? 1) All hydrocarbons keep their original properties, such as their condensing points. The properties of a mixture are just a mixture of the properties of the separate parts. 2) The parts of a mixture can be separated out by physical methods, e.g. crude oil can be split up into its separate fractions by fractional distillation. Each fraction contains molecules with a similar number of carbon atoms to each other.
How does fractional distillation work and What are the name, lengths and condensing temperatures of each specific fraction starting from the bottom? 1) The fractionating column work continuously, with heated crude oil piped in at the bottom. The vaporised oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense. The column get colder further up it is hottest at the bottom. The molecule length also decreases the further up the column you go. 2) The names, length and condensing temperatures of specific fractions: a) Bitumen has a molecule length of 40 and is the first to condense at above 340 degrees. b) Oil has a molecule length of 35 and condenses at 340 degrees. c) Diesel has a molecule length of 20 and condenses at 250 degrees. d) Kerosene (jet fuel) has a molecule length of 15 and condenses at 180 degrees. e) Naphtha has a molecule length of 10 and condenses at 110 degrees. f) Petrol has a molecule length of 8 and condenses at 40 degrees. g) Refinery gas (bottled gas) has a molecule length of 3 and come out at the top of the column.
What are hydrocarbons? 1) All fractions of crude oil are hydrocarbons called alkanes.
What are alkanes? 1) Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms. 2) Different alkanes have chains of different lengths.
What are the first 4 alkanes? 1) The first four alkanes are Methane which is natural gas (CH4), Ethane (C2H6), Propane (C3H8) and Butane (C4H10).
How many bonds can carbon and hydrogen atoms for? What does saturated mean? 1) Carbon atoms form four bonds and hydrogen atoms only form one bond. Alkanes have formed bonds with as many other atoms as they can this means they're saturated.
What is the general formula for alkanes? Use the formula to work out how many hydrogens an alkane with 5 carbon atoms would have. 1) Alkanes all have the general formula CnH2n+2. 2) If an alkane has five carbons it's got to have (2x5)+2 = 12 hydrogens.
What are the basic trends for alkanes? 1) The shorter the molecules, the more runny the hydrocarbon is - that is, the less viscous (gloopy) it is. 2) The shorter the molecules, the more volatile they are. "More volatile" means they turn into a gas at a lower temperature. So, the shorter the molecules, the lower the temperature at which that fraction vaporises or condenses - and the lower its boiling point. 3) Also, the shorter the molecules, the more flammable (easier to ignite) the hydrocarbon is.
How do the uses of hydrocarbons depend on their properties? 1) The volatility helps decide what the fraction is used for. The refinery gas fraction has the shortest molecules, so it has the lowest boiling point - in fact it's a gas at room temperature. This makes it ideal for using as bottled gas. It's stored under pressure as liquid in 'bottles'. When the tao in the bottle is opened, the fuel vaporises and flows to the burner where it's ignited. 2) The petrol fraction has longer molecules, so it has a higher boiling point. Petrol is a liquid which is ideal for storing in the fuel tank of a car. It can flow to the engine where it's easily vaporised to mix with the air before it is ignited. 3) The viscosity also helps decide how the hydrocarbons are used. The really gloopy, viscous hydrocarbons are used for lubricating engine parts and for covering roads.
How are crude oil provide important fuels for modern life? 1) Crude oil fractions burn cleanly so they make good fuels. Most modern transport is fuelled by a crude oil fraction, e.g. cars, boats, trains and planes. Parts of crude oil are also burned in in central heating systems in homes and in power stations to generate electricity. 2) There's a massive industry with scientists working to find oil reserves, take it out of the ground, and turn it into useful products. As well as fuels, crude oil also provides the raw materials for making various chemicals, including plastics.
What are the alternatives to using crude oils? 1) Often, alternatives to using crude oil fractions as fuel are possible. E.g. electricity can be generated by nuclear power or wind power, there are ethanol-powered cars, and solar energy can be used to heat water.
What are the negatives of using the alternatives to crude oil? 1) Things tend to be set up for using oil fractions. For example, cars are designed for petrol or diesel and it's readily available. There are filling stations all over the country, with storage facilities and pumps specifically designed for these crude oil fractions. So crude oil fractions are often the easiest and cheapest thing to use. 2) Crude oil fractions are often more reliable too - e.g. solar and wind power won't work without the right weather conditions. Nuclear energy is reliable, but there are lots of concerns about its safety and the storage of radioactive waste.
What do scientists predict will happen to crude oil? 1) Most scientists think that oil will run out - it's a non-renewable source. 2) No one knows exactly when it'll run out but there have been heaps of different predictions - e.g. about 40 years ago, scientists predicted that it'd all be gone by the year 2000.
What are the scenarios for running out of crude oil? 1) New oil reserves are discovered from time to time and technology is constantly improving, so it's now possible to extract oil that was once too difficult or expensive to extract. 2) In the worst-case scenario, oil may be pretty much gone in about 25 years.
What are the solutions to the problem of running out of crude oil? 1) Some people think we should immediately stop using oil for things like transport, for which there are alternative, and keep it for things that it's absolutely essential for, like some chemicals and medicines. 2) It will take time to develop alternative fuels that will satisfy all our energy needs. It'll also take time to adapt things so that the fuels can be used on a wide scale. E.g. we might need different kinds of car engines, or special storage tanks built. 3) One alternative is to generate energy fro renewable sources - these are sources that won't run out. Examples of renewable energy sources are wind power, solar power and tidal power. 4) So however long oil does last for, it's a good idea to start conserving it and finding alternatives now.
How is crude oil not always environmentally friendly? 1) Oil spills can happen as the oil is being transported by tanker - this spells disaster for the local environment. Birds get covered in the stuff and are poisoned as they try to clean themselves. Other creatures, like sea otters and whales, are poisoned too. 2) You have to burn oil to release the energy form it. But burning oil is thought to be a major cause of global warming, acid rain and global dimming.
What is released when you burn fossil fuels? 1) Power stations burn huge amounts of fossil fuels to make electricity. Cars are also a major culprit in burning fossil fuels. 2) Most fuels, such as crude oil and coal, contain carbon and hydrogen. During combustion, the carbon and hydrogen are oxidised so that carbon dioxide and water vapour are released into the atmosphere. Energy (heat) is also produced. e.g: hydrocarbon + oxygen = carbon dioxide + water vapour. 3) If the fuel contains sulfur impurities, the sulfur will be released as sulfur dioxide when the fuel is burnt. 4) Oxides of nitrogen will also form if the fuel burns at a high temperature. 5) When there's plenty of oxygen, some of the fuel doesn't burn - this is called partial combustion. Under these conditions, solid particles (called particulates) of soot (carbon) and unburnt fuel are released. Carbon monoxide (a poisonous gas) is also released.
How does sulfur dioxide and nitrogen cause acid rain? 1) Sulfur dioxide id one of the gases that causes acid rain. 2) When sulfur dioxide mixes with clouds it forms dilute sulfuric acid. This then falls as acid rain. 3) In the same way, oxides of nitrogen cause acid rain by forming dilute nitric acid in clouds.
What are the effects of acid rain? 1) Acid rain causes lakes to become acidic and many plants and animals die as a result. 2) Acid rain kills trees and damages limestone buildings and ruins stone statues. 3) Links between acid rain and human health problems have been suggested. 4) The benefits of electricity and travel have to be balanced against the environmental impacts. Governments have recognised the importance of this and international agreements have been put in place to reduce emissions of air pollutants such as sulfur dioxide.
How can you reduce acid rain? 1) Most of the sulfur can be removed from fuels before they're burnt, but it costs more to do it. 2) Also, removing sulfur from fuels takes more energy. This usually comes from burning more fuel, which releases more of the greenhouse gas carbon dioxide. 3) However, petrol and diesel are starting to be replaced by low-sulfur versions. 4) Power stations now have Acid Gas Scrubbers to take the harmful gases out before they release their fumes into the atmosphere. 5) The other way of reducing acid rain is simply to reduce our usage of fossil fuels.
How is the increasing amount of carbon dioxide causing climate change? 1) The level of carbon dioxide in the atmosphere is increasing - because of the large amounts of fossil fuels humans burn. 2) There's a scientific consensus that this extra carbon dioxide has caused the average temperature of the Earth to increase - global warming. 3) Global warming is a type of climate change and causes other types of climate change, e.g. changing rainfall patterns. It could also cause severe flooding due to the polar ice caps melting.
How do particles cause global dimming? 1) In the last few years, some scientists have been measuring how much sunlight is reaching the surface of the Earth and comparing it to records from the last 50 years. 2) They have been amazed to find that in some areas nearly 25% less sunlight has been reaching the surface compared to 50 years ago. They have called this global dimming. 3) They think that it is caused by particles of soot and ash that are produced when fossil fuels are burnt. These particles reflect sunlight back into space, or they can help to produce more clouds that reflect the sunlight back into space. 4) There are many scientists who don't believe the change is real and blame it on inaccurate recording equipment.
What are the pros and cons of using ethanol as an alternative (renewable) fuel? Ethanol can be produced from plant material so is know as a biofuel. It's made by fermentation of plants and is used to power cars in some places. It's often mixed with petrol to make a better fuel. 1) Pros: The carbon dioxide released when it's burnt was taken in by the plant as it grew so it's 'carbon neutral'. The only other product is water. 2) Cons: Engines need to be converted before they'll work with ethanol fuels. And ethanol fuel isn't widely available. There are worries that as demand for it increases farmers will switch from growing food crops to growing crops that make ethanol - this will increase food prices.
What are the Pros and Cons of using biodiesel as an alternative (renewable) fuel? Biodiesel is another type of biofuel. It can be produced from vegetable oils such as rapeseed oil and soybean oil. Biodiesel can be mixed with ordinary diesel fuel and used to run a diesel engine. 1) Pros: Biodiesel is 'carbon neutral'. Engines don't need to be converted. I t produces much less sulfur dioxide and 'particulates' than ordinary diesel or petrol. 2) Cons: We can't make enough to completely replace diesel. It's expensive to make. It could increase food prices like using more ethanol could.
What are the Pros and Cons of using hydrogen gas as an alternative (renewable) fuel? Hydrogen Gas can also be used to power vehicles. You get the hydrogen from the electrolysis of water - there's plenty of water about but it takes electrical energy to split it up. This energy can come from a renewable source e.g. solar. 1) Pros: Hydrogen combines with oxygen in the air to form just water - so it's very clean. 2) Cons: You need a special, expensive engine and hydrogen isn't widely available. You still need to use energy from another source to make it. Also, hydrogen's hard to store.
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