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Flashcards by finn squires, updated more than 1 year ago
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Created by finn squires
almost 7 years ago
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| Question | Answer |
| What are ceramics? | Ceramics are non-metal solids with high melting points that aren't made from carbon-based compounds. |
| Explain how ceramics can be made from clay? | Clay is a soft material so can be moulded. When its fired to high temperatures, it hardens to form a clay ceramic. It is ideal for pottery and bricks. |
| What are the two main types of glass and their properties? | Glass is usually transparent, mouldable when hot and brittle when thin. Soda-lime glass (common) - made by heating a mixture of limestone, sand and sodium carbonate (soda) until it melts. Mixture cools into glass. Borosilicate glass - has higher MP than soda-lime glass. Made in the same way, using a mixture of sand and boron trioxide. |
| What are composites? | Composites are made fo one material embedded in another. Fibres or fragments (reinforcements) are surrounded by a matrix acting as a binder. The properties of it depend n the properties of the materials its made from. |
| Give four examples of composites? | Fibreglass - glass in a matrix made of polymer. Low density (like plastic) but very strong (like glass). Carbon fibre - long chains of carbon or nanotubes in a polymer matrix. Strong and light. Concrete - aggregate (sand and gravel) in a cement matrix. Very strong. Wood - cellulose fibres in an organic polymer matrix. |
| Why are alloys needed? | The regular structure of pure metals makes them soft. Alloys are made by adding another metal and disrupts the structure of the metal making it harder than pure metals. For example, steels are made by adding carbon etc to pure iron. |
| Give four examples of alloys used in everyday life? | Bronze=copper+tin (bronze is harder than copper) - medals, statues Brass = copper+zinc (brass is more malleable than bronze when lower friction is needed) - Taps, door fittings Gold alloys (pure is very soft so zinc, copper and silver used to harden) - jewellery 24 carat is pure 18/24 = 75% gold. Aluminium alloys (pure is too soft but has low density so alloyed for strength). |
| What is corrosion? | Corrosion is where metals react with substances in their environment and are gradually destroyed. |
| What is the formula for the corrosion of iron (rust)? | Iron + oxygen + water ---> hydrated iron(III) oxide. |
| Explain how iron and steel erode a lot faster than aluminium? | The rust is a soft crumby solid that soon flakes off the surface of the iron leaving more iron available to rust again. This means eventually all the iron in an object corrodes away even if it wasn't initially on the surface. Aluminium is completely destroyed by corrosion as the aluminium oxide that forms doesn't flake away meaning it forms a protective layer that sticks firmly to the surface stopping further reactions taking place. |
| Describe the experiment used to show what is needed for iron to rust? | 1. to show water alone is not enough for iron to rust; put an iron nail in a boiling tube with just water and the nail won't rust (water is boiled to remove oxygen and oil is used to stop air getting in). 2. to show that oxygen alone is not enough; put an iron nail in a boiling tube and it won't rust (calcium chloride can be used to absorb any water from the air). 3. to show both water and air are needed; put an iron nail in a tube with air and water, it will rust. |
| Explain how the mass of the iron nail will increase when rust has formed? | The mass of the rusty nail will increase as the iron atoms in the nail have now bonded to oxygen and water molecules, resulting in a compound that is heavier than iron alone. |
| Give three examples of coating the iron to prevent rusting? | Painting/coating with plastic - ideal for big/small structures. Electroplating - this uses electrolysis to reduce metal ions onto an iron electrode. it can be used to coat the iron with a layer of a different metal that won't be corroded away. Oiling/greasing - this has to be used when moving parts are involved e.g. bike chains. |
| Explain what a sacrificial method to prevent rusting is? | This involves placing a more reactive metal, such as zinc or magnesium, with the iron. Water and oxygen then react with the sacrificial metal instead of with the iron. |
| Give an example of a protection technique that uses both types of methods? | An object can be galvanised by spraying it with a coating of zinc. The zinc layer is firstly protective, but if it's scratched, the zinc around the site of the scratch works as a sacrificial metal. |
| What are natural resources? | Natural resources form without human input. They include anything that forms the earth, sea or air, e.g. cotton for clothing or oil for fuel. However, some of these natural resources are being replaced by synthetic products or improved by man-made processes. For example, rubber is a natural product from tree sap, however, man-made polymers have now replaced its uses like tyres. Agriculture provides conditions where natural resources can be enhanced for our needs. E.g. the development of fertilizers have meant we can have a high yield of crops. |
| What are renewable resources? | Renewable resources reform at a similar to, or faster rate than we use them. For example, timber is a renewable resource because trees can be planted and only take a few years to regrow. Also, fresh water and food are renewable. |
| What are finite (non-renewable) resources? | Finite resources, arent formed quickly enough to be considered replaceable. For example; fossil fuels, plutonium, uranium, minerals, metals. After these have been extracted they undergo man-made processes to provide fuels and materials necessary for modern life, e.g. crude oil-fractional distillation, ores-reduction (metal). |
| Name some social, economic and environmental effects of extracting finite materials? | More jobs, more money, uses lots of energy, scars the landscape, lots of waste, destroys habitats. |
| Name two ways in which we can improve copper's sustainability? | One way of improving its sustainability is extracting it from low-grade ores; Bioleaching - bacteria used to convert copper compounds in the ores into soluble copper compounds, separating the copper from the ore in the process. The leachate (solution produced) contains copper ions which can be extracted by electrolysis or displacement using scrap iron. Phytomining - Growing plants in soil containing copper. The plant's cant use or get rid of the copper so it gradually builds up in the leaves. The plants then are harvested, dried and burned, the ash contains copper compounds from which copper can be extracted by electrolysis or displacement using scrap iron. These methods are slow but have a smaller impact on the environment. |
| What is a life cycle assessment (LCA)? | A life cycle assessment looks at every stage of a products life to assess its impact on the environment. |
| What are the four main stages that need to be considered when making a lifestyle assessment? | 1. getting the raw materials - can damage the environment, pollution as lots of energy from fossil fuels needed, processing also needs a lot of energy. 2. manufacturing and packaging - pollution as uses lots fo energy, waste disposal (some can be useful). 3. using the product - can damage the environment (fuel burning, fertilisers leaching), how long a product is used for and how many uses it has (lots energy needed to make but used for a long time=less waste in long run). 4. product disposal - landfill pollution, energy used to transport the waste, inceration pollution. |
| What are the main problems with LCAs? | Use of energy, natural resources and waste produced is easy to quantify. But the effect of some pollutants is harder to give a numerical value to. Therefore LCAs are biased as it takes into account the values of the person carrying out the assessment. Selective LCAs only take in some of the impacts of a product on the environment, can also be biased as they can be deliberately written to give a company positive advertising. |
| What is potable water? | Potable water is water that has been treated or is naturally safe for humans to drink. However, it's not pure as it contains other molecules rather than just H2O. Levels of dissolved salts aren't too high and it has a pH between 6.5 and 8.5 and also there aren't any pathogens in it. |
| What are the two important things that influence the properties of a polymer? | How its made and what its made from. |
| What do the properties of poly(ethene) depend on? | The properties of poly(ethene) depend on the catalyst that was used and the reaction conditions (temp+press) that it was made under. Low-density poly(ethene) is made from ethene at a moderate temp under a high pressure and with a catalyst. It's flexible and is used for bags and bottles. High-density poly(ethene) is also made from ethene but at a lower temp and pressure with a different catalyst. It's more rigid and is used for water tanks and drain pipes. |
| How does what a polymer is made from affect its properties? | The monomers that a polymer is made from determines the type of bonds that form between the polymer chains. These weak bonds between the different molecule chains determine the properties of the polymer: thermosetting polymer or thermosoftening polymer. |
| What is a thermosetting polymer? | Thermosetting polymers contain monomers that can form cross-links between the polymer chains, holding the chains together in a solid structure. They do not soften when heated, they are strong, hard and rigid. |
| What is a thermosoftening polymer? | Thermosoftening polymers contain individual polymer chains entwined together with weak forces between the chains. You can melt these polymers and remould them. |
| How is potable water produced in places like the UK? | In warm areas of the UK, the surface freshwater usually dries up so in these areas the domestic water supply comes from the groundwater. Although it has low levels of dissolved substances in, water from these sources still needs to be treated to make it potable: Filtration - wire mesh screens out large objects, then sand and gravel beds filter out any other solid bits. Sterilisation - the water is sterilised to kill pathogens, done by bubbling chlorine gas through it or using ozone or ultraviolet light. |
| How is potable water produced in places which are very dry? | In some very dry countries there's not enough surface or groundwater and instead, seawater must be treated by desalination (using distillation) to provide potable water. Seawater can also be treated by reverse osmosis. The salty water is passed through a membrane that only allows water molecules through, ions and larger molecules are trapped by the membrane so are separated from the water. Both of these methods need lots of energy so are expensive and not practical for producing large quantities of fresh water. |
| Explain the practical for testing and distilling water? | 1. test the pH of the water, if it's too high/low then you need to neutralise it by adding acid if its high and alkali if its low. make it so its pH 6.5-8.5. 2. test the water for the presence of sodium chloride (seawater salt); test for sodium ions; do a flame test on a small sample (it will turn yellow). test for chloride ions; take a sample and add a few drops of dilute nitric acid, followed by a few drops of silver nitrate solution (white precipitate). 3. distil water; pour salty water into distillation apparatus and heat the flask from below. The water will boil and form steam, leaving the dissolved salts behind. The steam will condense back to liquid water in the condenser and can be collected as it runs out. 4. retest the distilled water for sodium chloride to check that it has been removed. Also, retest the pH to check that it's between pH 6.5 and 8.5. |
| What are the three main sources of wastewater? | Domestic use, agricultural systems and industrial processes. |
| What are the six stages of sewage treatment? | 1. screening - removing large bits of material (plastic bags etc) and grit. 2. sedimentation - allowed to stand in a settlement tank, the heavier suspended solids sink to the bottom to produce sludge, light effluent floats on top. 3. the effluent is removed and treated by biological aerobic respiration- air is pumped through the water to encourage aerobic bacteria to break down organic matter (including other microbes). 3. the sludge from the bottom of the settlement tank is also removed and transferred into large tanks - broken down by bacteria in anaerobic digestion releasing methane gas which can be used as an energy source. The remaining waste can also be used as a fertiliser. 6. for wastewater containing toxic substances, more stages of treatment may include; adding chemicals, UV radiation or using membranes. This requires more processes but uses less energy than the desalination of freshwater so could be an alternative in areas where there is not much freshwater. |
| What is the Haber process? | The Haber process is used to make ammonia from hydrogen and nitrogen using the following reaction: |
| Why is the Haber reaction well suited to an industrial scale? | The reaction is well suited to an industrial scale as the reactants aren't too difficult or expensive to obtain: 1. nitrogen found in air (78%). 2. hydrogen comes from reacting methane (from natural gas) with steam to form hydrogen and carbon dioxide. 3. the reactants are passed over an iron catalyst. A high temperature (450oC) and a high pressure (200 atmospheres) are used. |
| Explain what happens to the ammonia produced in the Haber process? | As the reaction is reversible, some of the ammonia produced converts back into hydrogen an nitrogen again. It eventually reaches dynamic equilibrium. The ammonia is formed as a gas, but as it cools in the condenser it liquefies and is removed. The unused hydrogen and nitrogen are recycled. The ammonia produced can be used to make ammonium nitrate which is a very nitrogen-rich fertiliser. |
| What are the two main ways of increasing the yield of ammonia? | 1. increasing pressure (it favours the side with the fewer moles of gas). 2. decreasing temperature (it favours the exothermic reaction). |
| What are the conditions needed for the Haber process? | - 450oC - compromise between rate and yield (lowish yield quickly) - 200 atm pressure - compromise between yield and cost (highish yield + lowish cost) - iron catalyst - increases rate not yield A low yield of 40% isn't too bad because the waste gas is recycled. |
| What are the main components used in the Haber process? | nitrogen and hydrogen mixer compressor catalyst chamber unreacted gases recycled chiller ammonia |
| What is the job of NPK fertilisers? | Farmers use manure to fertilise fields but formulated fertilisers are better as they are more available, easier to use, don't smell and have just enough of each nutrient so the plant can grow. The three main essential elements in fertilisers are nitrogen, phosphorous and potassium. These elements may be missing from the soil as the previous plants would have used them. Fertilisers replace these missing elements or provide more of them to increase yield. NPK fertilisers contain nitrogen, phosphorous and potassium salts in the right percentages. |
| How is ammonia used to make nitrogen-containing compounds? | Ammonia and nitric acid react (neutralisation) to produce ammonium nitrate (very good fertiliser as it contains nitrogen from two sources): |
| Where is each of the NPK salts from? | N salts from neutralisation reaction. P salts are made by dissolved phosphate rocks in acid. K salts are made from soluble rock salts. |
| Compare how ammonium nitrate is made in a lab/industry? | Industry; giants vats @ high concs = very exothermic. Heat used to evaporate water from the mixture to make a very concentrated ammonium nitrate product. Lab; smaller scale, lower conc, safer, after titration, crystallisation to give pure ammonium nitrate crystals, crystallisation is very slow. |
| What are the three phosphate rock reactions? | 1. reaction with nitric acid produces phosphoric acid and calcium nitrate. 2. reaction with sulfuric acid produces calcium sulfate and calcium phosphate (this mixture is known as single superphosphate) 3. reaction with phosphoric acid only produces calcium phosphate (the product of this reaction can be called triple superphosphate). |
| How are different materials suited to different jobs? | Ceramics (include glass and clay) - ceramics such as porcelain and bricks. Good conductors of heat/electricity, brittle and stiff. Polymers - insulators of heat/electricity, can be flexible and easily moulded. Metals - usually malleable, good conductors of heat/electricity, ductile, shiny and stiff. Composites - properties depend on matrix/binder and the reinforcement used to make them, so have different uses. |
| How is Chemistry improving sustainability? | -sustainable development is an approach to development that takes account of the needs of present society while not damaging the lives of future generations. -as well as using resources, extracting resources can be unsustainable due to the amount of energy used and waste produced. Processing the resources into useful materials, such as glass or bricks, can be unsustainable too as the processes often use energy that is made from finite resources. - if people reduce how much they use of a finite resource, that resource is more likely to last longer, this will also reduce the use of anything needed to produce them. -chemists can develop and adapt processes that use lower amounts of finite resources and reduce damage to the environment, e.g. chemists have developed catalysts that reduce the amount of energy requires for certain industrial processes. |
| Explain how recycling metals is important? | 1. mining and extracting metals takes lots of energy, most of which comes from burning fossil fuels. 2. recycling metals often uses much less energy than is needed to mine and extract new metal, conserves the finite amount of each metal in the earth and cuts down on the amount of waste getting sent to landfill. 3. metals are usually recycled by melting and casting into the shape of the new product. 4. depending on what the metal will be used for after recycling, the amount of separation required for recyclable metals can change, e.g. waste steel and iron can be kept together as they can be both added to iron in a blast furnace to reduce the amount of iron ore required. |
| Explain how glass can be recycled? | 1. Glass bottles can be reused without reshaping. 2. other forms of glass cant be reused so they're recycled instead. Usually, the glass is separated by colour and chemical composition before being recycled. 3. the glass is crushed and then melted to be reshaped for use in glass products such as bottles or jar. It might also be used for a different purpose such as insulating glass wool for wall insulation in homes. |
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