C1 New and improved

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When are ionic bonds formed?
When a metal reacts with a non-metal –ions formed, metal atoms lose 1 or more electrons to form positively charged ions + Non-metals gain electrons to form neg ions. Opp charged ions attract.
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When are covalent bonds formed?
When non-metals combine to form molecules. These bonds can be shown in diagrams as lines between the atoms joined together.
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What can we use limestone for?
Cement =limestone mixed with clay and heated strongly in a kiln. Mortar = cement mixed with sand + water –used to hold bricks and blocks together in buildings. Concrete = cement, sand, water + aggregate. Small stones used for aggregate.
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What happens when limestone is heated strongly?
It undergoes thermal decomposition to make CaO and CO2. This is done on a large scale in lime kilns.
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How do all metal carbonates react when heated?
Metal carbonates decompose to the metal oxide & carbon dioxide when heated strongly enough. A Bunsen burner can’t get hot enough to decompose sodium carbonate or potassium carbonate.
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How do all metal carbonates react with acid?
All produce a salt, water + CO2 gas. Limestone is damaged by acid rain as the CaCO3 in the limestone reacts with acids in the rain. CaOH solution = limewater (used to test for CO2) as it turns cloudy –reacts with CO2 -->insoluble CaCO3.
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Describe the limestone reaction cycle.
Limestone (CaCO3) decomposed by heating (thermal decomposition) to make CaO + CO2 --> CaO reacts with water to produce calcium hydroxide -->Add more water + filter = limewater-->Add CO2 = CaCO3.
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How is calcium hydroxide used?
As an alkali + can be used to neutralise acids i.e. used by farmers to neutralise acidic soils and in industry to neutralise acidic gases.
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What are the pros and cons for an area where limestone is to be quarried?
Pros: More employment opportunities for locals, more customers, improved roads + trade for local businesses. Cons: dust + noise, more traffic, loss of habitats for wildlife.
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What is an ore?
A rock that contains enough of a metal or a metal compound to make it worth extracting the metal. Mining ores often involves digging up a lot of rock + ore may need to be concentrate before extracted –can produce a lot of waste -environment.
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What kinds of metal can be found in the earth as the metal i.e. Gold?
Unreactive metals, low in the reactivity series. Gold can be separated from rock by physical measure. However, most metals are found as compounds and have to be extracted by chemical reactions.
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Metals can be extracted from compounds by displacement using a more reactive element. What is reduction?
Metals which are less reactive than Carbon can be extracted from their oxides by heating with carbon. Reduction is a reaction that takes place as carbon removes the oxygen from oxide to produce the metal.
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Many of the ores used to produce iron contain iron (III) oxide. How is iron (III) oxide reduced?
At high temperatures in a blast furnace using carbon. The iron produced contains about 96% iron. The impurities make it hard and brittle and so it has only a few uses as cast iron.
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Why is most iron used to make steels?
As pure iron is too soft. Steels are alloys of iron (mix of iron with carbon etc.). Alloys can be made so that they have properties for specific uses. Stainless steels resist corrosion. Low-carbon steel = easily shaped & high carbon steels are hard.
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Describe the properties of aluminium.
Low density, high in reactivity series but resistant to corrosion. Pure aluminium isn’t very strong, but Al alloys are stronger and harder.
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How is aluminium extracted?
More reactive than carbon + so its oxide can’t be reduced using carbon + so has to be extracted by electrolysis of molten aluminium oxide –requires high temp + lot of electricity = expensive.
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Describe some properties of titanium.
Resistant to corrosion + very strong. Has low density compared with other strong metals.
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How can titanium be extracted?
Titanium oxide can be reduced by carbon but the metal reacts with carbon making it brittle. Titanium is extracted from its core by a process that involves large amounts of energy = expensive.
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How can copper be extracted?
From copper rich ores by smelting (heating the ore strongly in a furnace) –produces impure copper which can be purified by electrolysis. Smelting + purifying copper ore require huge amounts of heating + electricity.
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Copper-rich ores are a limited resource. Describe two methods scientists are developing to extract copper from low-grade ore (which can have less environmental impact).
Phytomining: uses plants to absorb copper compounds from the ground. The plants are burned + produce ash from which copper can be extracted. Bioleaching: uses bacteria to produce solutions containing copper compounds.
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Describe two ways other than smelting used to extracts copper.
Solutions of copper compounds can be reacted with a metal that is more reactive than copper i.e scrap iron to displace the copper. Copper can also be extracted from solutions of copper compounds by electrolysis.
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Describe copper.
Good conductor of heat, doesn’t react with water. Can be bent but is hard enough to keep its shape = useful for making pipes + tanks in water + heating systems. Good conductor of electricity – wiring.
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Why should we recycle metals?
Saves the energy needed to extract the metal, saves resources as less ore needs to be mined. Also less fossil fuels needed to provide energy to extract metal from its ore.
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What are the benefits and drawbacks of using metals in construction?
Pros: Strong, malleable, ductile + are good conductors of heat/electricity. Cons: Obtaining metals from ores causes pollution + uses up limited resources, more expensive than other materials + some rust.
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Why must we separate the hydrocarbons in crude oils?
As it contains many different compounds that boil at different temps. Burn under different circumstances and so crude oil must be separated to make useful fuels.
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Why is it possible to separate a mixture by physical methods i.e. distillation?
As a mixture consists of 2 or more elements or compounds not chemically combined together + the chemical properties of each substance is unchanged in a mixture.
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How is crude oil separated into fractions?
Fractional distillation – hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by evaporating the oil + allowing it to condense at different temperatures.
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What is the difference between fractional and simple distillation?
Simple distillation is done in steps by heating the mixture to different temps. Fractional distillation is done continuously by vaporising the mixture and condensing the fractions into different temperatures.
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Why are fractions with low boiling ranges useful as fuels?
Fractions with low boiling ranges have low viscosity (runny liquids) –flammable so ignite easily + burn with clean flames, producing little smoke.
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What happens when pure hydrocarbons burn completely?
They are oxidised to carbon dioxide and water. However the fuels we use are not always burned completely –also contain other substances.
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Name four possible products of the incomplete combustion of a hydrocarbon.
In a limited supply of air, incomplete combustion may produce: carbon monoxide, carbon, solid particles that contain soot (carbon) + unburnt hydrocarbons called particulates.
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What is produced when fuels are burned?
Sulfur dioxide and nitrogen oxide (nitrogen and oxygen react due to the high temperatures fuels are burned at) both cause acid rain.
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Describe the negative impact of burning fuels on the environment?
CO2 (greenhouse gas) causes global warming. Incomplete combustion of these fuels produces poisonous carbon monoxide. It can also produce particulates that reflect sunlight and so cause global dimming.
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How can we remove harmful substances from waste gases before they are released into the atmosphere? For example sulfur is removed from fuels before they’re supplied to users (so less sulfur dioxide is produced when fuel is burned).
Sulfur dioxide is removed from waste gases from power stations. Exhaust systems of cars fitted with catalytic converters to remove carbon monoxide + nitrogen oxides. Filters can remove particulates.
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What is biofuels and biodiesel?
Biofuels are made from plant or animal products and are renewable. Biodiesel can be made from vegetable oils extracted from plants.
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What are advantages of using biodiesel?
It makes little contribution to CO2 levels as the CO2 given off when burned was taken from the atmosphere by plants as they grew (carbon neutral).
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What are disadvantages of using biodiesel? Give an example of a biofuel.
The plants grown for biodiesel use large areas of farmland. Ethanol made from sugar cane/beet = biofuel. It’s a liquid + can be stored/distributed like other liquid fuels-can be mixed with petrol.
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What are advantages and disadvantages of using hydrogen as a fuel?
Pros: only produces water when burned. Cons: As it’s a gas it takes up a large volume making it difficult to store in the quantities needed for combustion in engines. Produced from water by electrolysis = expensive, lots of energy.
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How are large hydrocarbons broken down into smaller molecules?
By cracking (two methods): by heating a mixture of hydrocarbons vapours + steam to a very high temp or by passing hydrocarbon vapours over a hot catalyst.
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What are alkanes?
Saturated hydrocarbons produced by thermal decomposition reactions during cracking. General formula CnH2n+2. The alkanes with smaller molecules are more useful as fuels.
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What are alkenes (also produced by cracking)?
Unsaturated hydrocarbons (CnH2n) as they contain fewer hydrogen atoms than alkanes with the same no. of carbon atoms. Alkenes have a double bond between 2 carbon atoms + this makes them more reactive than alkanes.
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How do alkenes react with bromine water?
As Alkenes have a double bond between 2 carbon atoms they are more reactive than alkanes and so react with bromine water turning it from orange to colourless.
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What is polymerisation?
Polymers are made (polymerisation reaction) from many monomers (small molecules) joined together – the double bond in each alkene molecule becomes a single bond + thousands join in chains.
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Why can’t alkanes polymerise?
As they are saturated hydrocarbons and only have a single bond.
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What is a shape memory polymer?
Polymers that change back to their original shape when temperature or other conditions are changed.
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Give two medical uses of polymers.
Dental fillings, hydrogels (polymers that can trap water- useful as dressings for wounds), light sensitive polymers (in sticking plasters to cover wounds so that they’re easily removed).
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Give two non-medical uses of polymers.
Can coat fibres used to make fabrics to make them waterproof + breathable. Plastic bottles/bags/containers + toys.
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What is the problem with many polymers not being biodegradable?
This means that plastic waste isn’t broken down when left in the environment –harmful to wildlife, unsightly + take up valuable space in landfill sites. Often can’t be recycled but sorting is difficult.
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Biodegradable plastics can be broken down by micro-organisms. Give an example.
Plastics made from non-biodegradable polymers can have cornstarch mixed intro the plastic. Micro-organisms break down the cornstarch so the plastic breaks down into very small pieces that can be mixed with soil or compost.
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Ethanol has the formula C2H6O and as it has the OH group, is an alcohol. Describe the two methods used to make ethanol.
Fermentation of sugar from plants using yeast –enzymes in yeast cause sugar to convert to ethanol + CO2. Hydration of ethene: ethene reacted with steam at a high temp in the presence of a catalyst. Ethene from crude oil by cracking.
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What are the advantages and disadvantages of producing ethanol by fermentation?
Uses a renewable resource (sugar from plants). Done at room temp but can only produce a dilute aqueous solution of ethanol. The ethanol must be separated from the solution by fractional distillation to give pure ethanol.
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What are the advantages and disadvantages of producing ethanol by hydration?
Produced from ethene uses a non-renewable resource, crude oil. The reaction can be run continuously + can produces pure ethanol, but requires a high temperature.
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How can vegetable oils be extracted from seeds, nuts and fruits?
By crushing + pressing the plant material & then removing water + other impurities. Some oils are extracted by distilling the plant material mixed with water –produces a mixture of oil + water from which the oil can be separated.
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Why do vegetable oils reacts with bromine water, turning it from orange to colourless?
As they have hydrocarbon chains. Those with carbon, carbon double bonds are unsaturated. If there are several double bonds in each molecule = polyunsaturated. Unsaturated oils react with bromine.
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Why is food cooked in vegetable oil?
The boiling points of vegetable oils are higher than water, so food is cooked at higher temp in oil =cooked faster. Also increases the energy content of the food.
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What is hydrogenation?
When unsaturated oils are reacted with hydrogen at about 60oC using a nickel catalyst so that some or all carbon-carbon double bonds become single bonds. The hydrogenated oils have higher melting points as they are unsaturated.
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Why is hydrogenation also called hardening?
As the hydrogenated oils are solids at room temperature (they have higher melting points as they are unsaturated) – can be used as spreads + to make pastries/cakes requiring solid fats.
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What is an emulsion?
A mixture of immiscible substances (oil + water) that when shaken, stirred or beaten together, form tiny droplets that can be slow to separate –opaque + thicker
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What are the useful properties of emulsion and how can they be used?
Opaque and thicker than the oil + water they’re made from –improves texture, appearance + ability to coat + stick to solids i.e. milk, cream, salad dressings, many cosmetic creams + some water-based paints.
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What are emulsifiers?
Substances that help stop the oil + water from separating into layers. Most emulsions contains emulsifiers to keep the emulsion stable.
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Emulsifier molecules have a hydrophilic part (head) attracted to water. The hydrophobic part (tail) is attracted to oil. How do emulsifiers work?
The hydrophobic parts go into each oil droplet + so the droplets become surrounded by hydrophilic parts –keeps droplets apart in water, preventing the oil droplets from joining together + separating out.
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What are the drawbacks of using vegetable oils?
Hydrogenated vegetable oils + animal fats contain saturated fats-linked to heart disease. Emulsifiers make food creamier + more palatable. Vegetable oils contain unsaturated fats = healthier than saturated.
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The earth has a diameter of 12, 800. Describe the structure of the earth.
Core: made up of iron + nickel (half diameter of earth)-liquid outer core + solid inner core. Mantle: 3000km (halfway) thick, semi-solid. 3. Crust: thin layer (between 5-70km). 4. Atmosphere: within 10-100km of surface.
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Scientists believe the Earth’s crust + upper part of the mantle is cracked into tectonic plates. What makes the tectonic plates move a few cm every year?
Convection currents in the mantle beneath them caused by energy/heat released by the decay of radioactive elements. When tectonic plates meet, huge forces build up causing earthquakes, volcanoes or mountains to form.
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Why didn’t other scientists accept Alfred Wegner’s idea of continental drift in 1915?
As he couldn’t explain why the continents moved. They believed that the Earth was shrinking as it cooled. In the 1960s scientists found new evidence + the theory of plate tectonics was developed.
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Describe the current atmosphere.
80% nitrogen, 20% oxygen + small proportion of other gases (CO2, water vapour + noble gases)
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Why has the amount of carbon dioxide in the atmosphere decreased since the early atmosphere?
CO2 dissolved in the oceans + became “locked up” in sedimentary rocks (i.e. limestone formed from shells/skeletons of marine organisms) + fossil fuels.
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What do scientists think about the Earth and its early atmosphere?
In first bill years, the surface was covered with volcanoes that released CO2, water vapour + oxygen. As earth cooled the water vapour condensed to form oceans. Some believe there may have also been ammonia, nitrogen + methane.
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What happened in the next two billion years (after the first 1 bill years) in earth’s early atmosphere?
Next 2 bill years: algae/plants evolved, used CO2 for photosynthesis + released oxygen. As no. of increased, the amount of CO2 in atmosphere decreased + O2 increased. Oceans also act as reservoir for CO2 + increased CO2 absorbed by oceans impacts mar
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How did Miller and Urey conduct the Miller-Urey experiment (based on what scientists at the time thought was in the early atmosphere) in 1952?
Used mixture of water, ammonia, methane + hydrogen and a high voltage spark to simulate lightning. After a week they found that amino acids (building blocks for proteins) were produ
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How can gases in the air be separated?
Liquid air can be separated by fractional distillation as the gases have different boiling points. Often done industrially to produce O2 + Nitrogen. Air is cooled to below -200C + fed into a fd column. N2 separated from O2 + argon
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Card 2

Front

When are covalent bonds formed?

Back

When non-metals combine to form molecules. These bonds can be shown in diagrams as lines between the atoms joined together.

Card 3

Front

What can we use limestone for?

Back

Preview of the front of card 3

Card 4

Front

What happens when limestone is heated strongly?

Back

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Card 5

Front

How do all metal carbonates react when heated?

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