Chem Unit 1

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Limestone cycle
Steps below
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Thermal decomposition: CaCO3 ---> CaO + CO2
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CaO(s) + H2O(l) (just enough) ---> Ca(OH)2(s)
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Ca(OH)2(s) + H2O(l) (excess) ---> Ca(OH)2(aq)
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Ca(OH)2(aq) + CO2(g) ---> CaCO3 + H2O
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Limestone and acid equation
Calcium Carbonate + X Acid ---> Calcium X + Carbon Dioxide + Water
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Uses of limestone:
Glass (heated with sand), Cement - heated with clay in a kiln. Concrete - mixed with sand, water and crushed rock (aggregate) Mortar - mixed with sand and water,
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Disadvantages of Quarrying (5)
1) Quarrying causes perm damage to environment 2) Noise pollution 3) Air pollution 4) Transporting it away causes more air pollution 5) Waste materials are put in tips
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Disadvantages of limestone (2)
1) Cement factories produce lots of dust, causing breathing problems. 2) Energy needed to produce quicklime. This energy is likely to come from fossil fuels (therefore pollution).
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Positives of Limestone Use (6)
1) Houses and roads 2) Chemicals in dyes paints medicines made from lime 3) Can neutralise acidic soil 4) Quarrying: jobs + infrastructure improvements 5) Neutralise Sulf Dioxide in power stations 6) Restoration of quarry site required when planned
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What makes limestone useful
1) Widely available + cheap 2) More hard wearing than marble + still looks good 3) Concrete poured into moulds to make bricks. Quick cheap and easy. 4) LiSt, Conc., Cem., don't rot like wood. 5) Fire resistant 6) Conc. doesn't corrode.
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Limestone has a low _____ strength.
Tensile. Therefore must be reinforced by steel bars.
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Define Ore
Rock containing enough metal that is economically viable to extract
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Ores are usually Metal _____
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Name of Aluminium ore:
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Factors influencing profitability of metal extraction (2)
1) Change in price of metal, 2) Improvements in technology
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Oxidation and Reduction (NOT OIL RIG)
Oxidation -- adding oxygen | Reduction -- removing oxygen
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3 ways of extracting metals from ores
Electrolysis (if more reactive than carbon), Reduction with carbon (if less reactive), Displacement (usually copper)
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E.g of Reduction with carbon equation (X Oxide)
X Oxide + Carbon ---> X + Carbon Dioxide
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Recall Electrolysis (page 53)
page 53
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What is the positive side of battery?
the longer one
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What is the negative side of battery?
the shorter one
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Fill in whether pos or negative Anode ( ) Anion ( ) Cathode ( ) Cation ( )
Anode ( - ) Anion ( + ) Cathode ( - ) Cation ( + )
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Electrolyte has ____ so that....
Freely moving ions so that the charge can flow and so that charge can move.
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Anode _____ electrons
Takes away
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Cathode ____ electrons
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Copper displacement equation:
Copper Sulfate + Iron ---> Iron Sulfate + Copper
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Copper rich ores are ______
in short supply
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2 methods to extract ores with small amounts of copper
Bioleaching, phytomining
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Bioleaching is
Separating copper from copper sulphide. Bacteria separate the bond between copper and sulfur, separating copper out from ore. The leachate can then be filtered for the copper.
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Grow plants in soil containing copper. Plants can't get rid of or use copper, so it builds up in leaves. Plants can then be harvested dried and burned in furnace, and the copper collected from the ash.
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1 pos and 1 neg of bioleaching and phytomining
pos: more environmentally friendly neg: theyre slow
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2 pos of extracting metals
1) Local infrastructure can be improved due to jobs and economy in area 2) Useful products can be made.
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4 cons
Causes noise, scarring of landscape, loss of habitats. Deep mine shafts can become dangerous for a long time after abandoned.
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Why recycling is important
Mining requires energy from fossil fuels. Fossil fuels are running out. Burning them contributes to acid rain, global dimming, and climate change. Recycling only uses small fraction of energy that is needed to mine. Recycling conserves resources.
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Why recycling is important
Reduces landfill.
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3 basic properties of metals
Strong, & malleable. Conductors of heat & electricity.
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Copper properties
Good conductor of electricity, hard strong but malleable, doesn't react with water. Ductile.
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Aluminium properties
Corrosion-resistant. Low density. Isn't strong, but forms hard alloys.
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Titanium properties
Low density, very strong, and corrosion resistant.
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Cast iron isn't used because
it's brittle
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Recall why pure metals are malleable.
Page 57
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Recall why alloys aren't as malleable
Page 57
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See book for steel.
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Crude Oil Definition
Mixture of different length hydrocarbon chains.
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4 steps of fractional distillation
1) Crude Oil Vaporised. 2) Bottom is very high temp, top is cooler 3) Hydrocarbons with low boiling point rise upwards and condense at the top of the column and vice versa. 4) They are tapped out.
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Trends: Flammability
Increases as length of hydrocarbon chain decreases
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Trends: Viscosity
Increases as length of hydrocarbon chain increases
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Colour change
Larger hydrocarbon chains are darker. Shorter ones are colourless.
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Gas Causing Global Warming
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Gas Causing Acid Rain
Nitrous Oxides, SO2 (as it reacts with rainwater to form HSO4)
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Gas Causing Global Dimming
Nitrous Oxides
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Pros of Ethanol Fuel
CO2 released when burnt is taken in by plant when it grew. Carbon neutral. Only other product is water.
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Cons of Ethanol Fuel
Engines need to be converted before they work with ethanol fuels. It's not widely available. Worries that demand will increase, meaning farmers will make crops for ethanol, not food, driving up prices.
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Steps of cracking
1) Thermal decomposition, so heated up. 2) Vapour passed over powdered catalyst at temperature of 400-700 *C. 3) Aluminium oxide is catalyst.
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How to make ethanol from ethene
React with water vapour in presence of catalyst. Cheap, but still uses non renewable source (ethene).
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Ethanol from renewable sources.
Fermentation. sugar ---> CO2 + Ethanol (lower temp and simpler equipment than ethene from steam).
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Problem with fermentation
Ethanol isn't very concentrated. It has to be distilled.
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Physical properties of polymer affected by
Temperature and pressure.
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Problem with polymers
They're not biodegradable.
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Why are vegetable oils used?
Higher boiling point so can be used to cook food at higher temperatures than water. Allows you to cook food quickly. Produces different flavours.
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Oil is used as...
Food and fuel as it provides energy.
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How to make vegetable oil.
Crush vegetable and distill it.
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Adding H2 @ 60*C, making it saturated.
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Emulsifiers allow:
stable suspension of vinegar/water and oil.
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Model answer about emulsifiers
Emulsifiers have hydrophobic tail and hydrophilic head. This allows them to form a bond between the oil and water, forming a stable suspension.
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What causes heat from the core?
Radioactive decay/processes of core releases heat causing convection currents.
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Wegener's theory of continent drift. Evidence found afterwards:
Borders of continent fit like jigsaw. Fossils and rocks similar/some found on different continents far away (this was dismissed with land bridge idea).
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Earth surface was molten. So hot, atmosphere boiled away. Thin crust formed, volcanoes kept erupting. Gave out gas. CO2, and water vapour given out by volcanoes. (And methane and ammonia). Oceans formed when water vapour condensed.
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Green plants and algae evolved. Lots of CO2 dissolved into oceans. Green plants photosynthesised this releasing O2. Algae and plants became fossils with hydrocarbons in them.
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Build up of oxygen killed off early organisms, allowed more complex organisms to evolve. Oxygen created O3 layer. This blocked out harmful radiation. Very little CO2 left in atmosphere.
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Primordial soup theory stages
1) nitrogen hydrogen ammonia and methane rich atmosphere 2) Lightning struck, causing chemical reaction. 3) Amino acids formed. 4) Amino acids collected in primordial soup, body of water. 5) This produced organic matter.
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Miller and Urey experiment
Gases > Electrical charge > some amino acids made, yet not enough. Suggests its along right lines.
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Fractional distillation of air
1) Air filtered. Removing dust. 2) Cooled to -200*C. 3) During cooling, water vapour condenses and is removed. 4) CO2 freezes and is removed. 5) Liquified air enters fractioning column and heated. 6) Remaining gases separated by fractional distil.
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They're passed through another column.
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