Chemistry- Unit 1

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What is the charge of a proton?
+1
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What is the charge of a neutron?
0
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What is the charge of an electron?
-1
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Where are protons and neutrons found in an atom?
In the nucleus
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Where are electrons found in an atom?
They orbit the nucleus
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What does the atomic number show?
The number of electrons and protons
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What does the mass number show?
The number of protons and neutrons
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Why is the overall charge of an atom neutral?
The number of protons and electrons are equal (NOT the charge)
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What is the maximum number of electrons in a shell?
2,8,8,2
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What does the group number show?
The number of electrons in the outer shell
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What are the characteristics of group 1?
Very reactive metals / 1 electron in their outer shell / react strongly with water / oxidise quickly
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What are the characteristics of group 0?
Noble gases / unreactive elements / outer shell completely full > stable and unreactive
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Why are noble gases unreactive?
They have a full outer shell
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What does the atom become if electrons are added or removed?
Charged and is then an ion
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What bonds form when a non-metal and metal react?
Ionic bonds
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What bonds form when two non-metals react?
Covalent bonds
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What is an element?
A substance that is made of only one type of atom
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What is the chemical formula for limestone?
CaCO3 = calcium carbonate
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What is the general equation for forming a salt?
Metal carbonate + acid > salt + water + Co2
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What is the limestone cycle?
Calcium carbonate is heated (Co2 is given off)> calcium oxide + water > calcium hydroxide + water > limewater > bubble Co2 in limewater > Limestone
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What are the uses of limestone?
Neutralising acids / Removes impurities (blast furnace) / concrete
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What is limestone used for?
As a building material and to make calcium oxide and cement
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When decomposed what does limestone make?
Calcium oxide and carbon dioxide
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What do metal carbonates decompose to when heated?
Metal oxide and carbon dioxide
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What are the advantages of quarrying?
Jobs for local people / Boosts economy as better-paid jobs / better healthcare and leisure facilities / better transport links / more building materials
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What are the disadvantages of quarrying?
Damage to the landscape / loss of wildlife habitats / noise/air/dust pollution / traffic congestion / expensive
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What is thermal decomposition?
The breakdown of a compound by heat
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How is cement made?
By heating limestone and clay. Used on its own and mortar/concrete
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How is mortar made?
Cement is mixed with sand and water. Mortar binds bricks together in walls.
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How is concrete made?
Cement is mixed with sand, aggregate, and water. Used for the foundations and buildings and structures like bridges.
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What is the difference between mortar and cement?
Cement, mortar and concrete don't dry out. Cement reacts with water to form crystals that keep the mixtures together. Mix of small sand particles in concrete make it stronger than mortar. Concrete can be made stronger by mixing it with steel.
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What is calcium hydroxide tested for?
Carbon dioxide. If Co2 is bubbles through limewater, it turns cloudy
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Why does limewater turn cloudy if Co2 is present?
Tiny solid particles of white calcium carbonate form
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Where are metals usually found?
In the Earth's crust
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How are unreactive metals found?
As a metal
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What is an ore?
Rock which contains enough metal to make it economically worthwhile to extract
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When are ores concentrated?
Before extraction and purification
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How can metals be extracted?
Displacement-using a more reactive element / Metals less reactive than carbon can be extracted from their oxides by heating with carbon
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What is a blast furnace?
Process to extract elements less reactive than carbon. Thermal decomposition reaction. Metal oxide + carbon > metal + Co2
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What is electrolysis?
Process to extract elements more reactive than carbon. A circuit is made with e.g. sulphuric acid which takes the element and separates it from the impurities
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How are metals more reactive than carbon extracted?
Electrolysis of molten compounds
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How can copper be extracted?
From copper-rich ores by smelting the ores strongly in a furnace
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Why does copper have to be purified?
Smelting produces impure copper
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How is copper purified?
Electricity is passed through solutions containing copper compounds like copper sulfate. during electrolysis, + charged ions move towards the - electrodes and are deposited as copper metal
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How else can copper be obtained?
From solutions of copper salts by displacement or electrolysis
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What are the uses of copper?
Electrical wiring and plumbing
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What is bioleaching?
Uses bacteria to produce leachate solutions containing metal compounds.
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What is phytomining?
Uses plants to absorb metal compounds from the ground. The plants are burned and produce ash from which the metal can be extracted.
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How is iron made from iron oxide?
It is reduced in a blast furnace
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What is the problem with iron made from the blast furnace?
It is too brittle for many uses
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How much iron is in iron from a blast furnace?
96%
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What is done with most iron?
It is converted into alloys called steels
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Why are metals more reactive than carbon expensive?
Large amounts of energy are needed to extract them
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What are the properties of low-carbon steel?
Easy to shape
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What are the properties of high-carbon steel?
Hard
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What are the properties of stainless steel?
Resistant to corrosion
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What are the properties of transition metals?
Good conductors of electricity and heat
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What are the properties of aluminium and titanium?
Low density and resistant to corrosion
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Why is pure copper, gold, iron and aluminium rarely used?
Too soft
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What is aluminium?
A low-density, corrosion-resistant metal used in many alloys
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How does aluminium have to be extracted?
By electrolysis which is very expensive as this process requires high temperatures and a lot of energy
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What is aluminium used for?
Drink cans / cooking foil / saucepans / high voltage electricity cable / airplanes / bicycles
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What is titanium?
A shiny, corrosion-resistant, very strong, low-density metal used to make alloys.
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How is titanium extracted?
It can be reduced by carbon but this makes it brittle. Extracted from its ore that involves several stages and a lot of energy so it's expensive
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What is titanium used for?
Bodies of planes and bikes / parts of jet engines / parts of nuclear reactors/ replacement hip joints
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Why should we recycle metals?
Extracting them uses limited resources
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What is crude oil?
A mixture of different compounds
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How is crude oil separated?
By distillation
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What are most of the compounds in crude oil?
Hydrocarbons
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What are hydrocarbons?
Compounds that contain only hydrogen and carbon atoms
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What are alkanes?
Saturated hydrocarbons with the general formula CnH2n+2
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Methane, Ethane, Propane, Butane
CH4, C2H6, C3H8, C4H10
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What is the main use for alkanes?
Fuel
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How are alkanes bonded together?
Covalently
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What makes alkanes similar to each other?
Only have single covalent bonds joining each atom together / Have similar structures so they react in similar ways
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Why can't alkanes react by adding extra atoms?
Each carbon atom in an alkane already has bonds to four other atoms
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What is fractional distillation?
A way to separate liquids from a mixture of liquids by boiling off the substances at different temperatures, then condensing and collecting the liquids
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What does the boiling point of hydrocarbon depend on?
The size of its molecule, the larger the molecule, the higher the boiling point of the hydrocarbon
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Why do boiling points depend on size?
Weak attractions between hydrocarbon molecules > small molecules there are fewer attractions between molecules > bigger molecules have more bonds, more attractions need to be broken down to separate molecules into a gas so they need more energy
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What is the process of fractional distillation of crude oil?
Crude oil is vapourised into a fractionating column > vapour rises to the top and cools > Hydrocarbons condense at different temperatures
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What are the properties of hydrocarbons as you go up the fractional distillation column?
Lower boiling points / lower viscosity / higher flammability
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What are the properties of shorter molecules?
Low boiling point, high volatility, high flammabilty
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What are the properties of longer molecules?
High boiling point, low volatility, low flammability
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What happens during combustion of hydrocarbon fuels?
Energy is released
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What happens when hydrocarbons are burned completely?
Complete combustion occurs and they are oxidised to carbon dioxide and water
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What is produced when hydrocarbons are burned in a limited supply of air?
Incomplete combustion occurs therefore carbon monoxide and solid particles may be produced
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What is produced when fuels containing sulfur compounds burn?
Sulfur dioxide
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What is produced when fuels are burned in extreme conditions?
Nitrogen oxides
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What are the three main problems with burning fuels?
Global warming from Co2 (CC) / Global dimming from the solid particles produced by IC / Acid rain from sulfur dioxide and nitrogen oxides
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Why are hydrocarbons cracked?
The hydrocarbons are broken down from larger molecules to smaller, useful fuels
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How do you crack hydrocarbons?
Heating and vaporising them / mixing them with a hot catalyst at about 600C (or steam at about 850C) / heated until thermal decomposition occurs
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How does using a catalyst help the reaction?
Allows the reaction to take place at a lower temperature than in steam cracking
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What is a catalytic converter?
It is fitted in a car to change carbon monoxide to carbon dioxide
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What happens in the reaction of a catalytic converter?
Reaction between nitric oxide and carbon monoxide takes place in the surface of a catalyst. Two gases formed are natural parts of air, nitrogen and carbon dioxide
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Why is there nitrogen oxide in exhaust gas?
The temperature of burning gas is high enough to cause some of the nitrogen in the combustion air to react with oxygen, that is also in the air, to form nitrogen oxide
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What are the products of cracking?
Alkanes and alkenes
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What are the products of cracking used as?
Fuel
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What are alkenes?
Unsaturated hydrocarbons containing double bonds with the general formula CnH2n
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Ethene, Propene, Butene
C2H4, C3H6, C4H8
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What makes alkenes more reactive than alkanes?
The double bonds are weak and easier to break, one of the bonds 'open up' to allow each carbon atom bond with another atom.
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What is the main use for alkenes?
To make polymers
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How do you detect double bonds?
Add bromine water to hydrocarbon > if hydrocarbon contains double bonds, orange BW turns colourless, it is unsaturated > if the orange BW remains, the hydrocarbon is saturated
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What happens when your clothes are wet?
The hydrocarbons can't accept any more water so they are saturated as the bonds are single
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What is a polymer?
A substance made from many small monomers joined together
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What is a monomer?
A small reactive molecule that react with other monomers in repeating sequences to form a polymer
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What is the process of polymerisation?
Monomers join together to form long molecules called polymers / reaction needs high pressure and a catalyst
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What happens to alkenes when they become a polymer?
The double bonds in the monomer become single bonds in the polymer when the molecules have joined together
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What are the properties of most polymers?
Low density / not brittle / corrosion resistant by chemicals / easily moulded into shape (soften when heated)
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What are the uses of polymers?
Packaging / waterproofing / dental / dressings / hydrogels
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What are natural materials of polymers?
Silk / Rubber / Starch / Proteins / DNA
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What is a shape-memory polymer?
They change back to their original shape when the temperature or other conditions are changed
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What is a smart polymer?
Polymers that change in response to changes in their environment
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What is a conducting polymer?
Polymers that can conduct electricity
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What is a light-emitting polymer?
Polymers that give off light when electricity passes through
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What does biodegradable mean?
Materials that can be broken down by microorganisms
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What is a biodegradable polymer?
Polymers that can rot away unlike other polymers that can cause waster problems
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How are plastic carrier bags biodegradable?
Made from polythene and corn starch > corn starch is decomposed by micro-organisms, leaving the polythene in microscopic pieces
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What is Biopol?
Biodegradable plastic produced by microorganisms > used in medicine to make stitches and hold bones together while they heal > it dissolves away so the stitches don't need to be removed
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How do you dispose polymers?
Dumping in landfills, recycling, burning in incinerators > The heat produced may be used to generate electricity or heat local buildings > wasteful of polymers and can cause air pollution
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What are the problems with non-biodegradable plastic?
It is unsightly / can damage the environment and harm wildlife / landfills take up too much space
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What are the problems with landfill sites?
Takes too much land that we are running out of space for / polymers take a long time to break down / destroy greenspaces and habitats
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What are the problems with incinerators?
Produces C02 which contributes to global warming
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What are the problems with recycling?
Difficult to separate different polymers / expensive
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How can these problems be reduced?
Use biodegradable polymers / recycle / use plastics mixed with cornstarch / collect litter for proper waste disposal
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How is ethanol produced?
Hydration / Fermentation
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What are the advantages of hydration?
Faster than fermentation / Continuous process / Produces pure ethanol
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What are the disadvantages of hydration?
Takes a lot of energy / uses fossil fuels which are non-renewable / needs to happen at high temperatures/pressures / expensive
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How is ethanol produced by fermentation?
Sugar from plants is turned into ethanol and Co2 / Enzymes and yeast act as a catalyst to make this reaction happen / product is a mixture of ethanol and water which can be separated by distillation
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What are the advantages of fermentation?
Uses less energy/ renewable materials / lower temperatures / normal pressure / less expensive
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What are the disadvantages of fermentation?
Takes longer / batch process / produces impure ethanol / needs to be in water and anaerobic respiration
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What is the process of extracting vegetable oils?
Plant material is crushed and pressed to squeeze oil out > oil can be dissolved in oil if difficult to extract > once oil is dissolved, solvent is removed by distillation and impurities such as water are removed to leave vegetable oil
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What are the advantages of cooking with vegetable oils?
Cooks faster due to higher boiling point
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What are the disadvantages of cooking with vegetable oils?
High use might cause someone to become overweight
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What do vegetable oils provide?
Lots of energy and important nutrients / used as fuels
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What happens to food when it is cooked in oil?
Cooks faster / flavour/colour/texture changes
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What is hydrogenation?
Unsaturated oils are reacted with hydrogen so double bonds become single > reaction is done at 600C using a nickel catalyst
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What are hydrogenated oils?
Oils that have been added to reduce the degree of unsaturation in the hardening process to make margarine
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What are the advantages of hydrogenation?
Different uses / longer shelf life
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What are the disadvantages of hydrogenation?
Turns into saturated fat > which is more likely to raise cholesterol
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What is an emulsion?
A mixture of liquids that do not dissolve in each other
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What are emulsifiers?
Substances that help keep immiscible liquids mixed so that they do not separate out into layers
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What are examples of emulsions?
Mayonnaise / ice cream
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What is the structure of an emulsifier molecule?
It has a small hydrophilic part and a long hydrophobic part > the hydrophilic head is attracted to water > the hydrophobic tail is attracted to oil
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How do emulsifiers keep the liquids mixed?
The hydrophobic parts of many emulsifiers go into each oil droplet so each droplet is surrounded by the hydrophilic parts. This keeps the droplets apart in water
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Which type of fat is better for your health?
Unsaturated fats
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What does the earth consist of?
Core / mantle / crust / atmosphere
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Where do Earth's resources come from?
The crust
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What are the properties of the crust and upper mantle?
Cracked into tectonic plates
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What is plate tectonics?
Convection current in the mantle causes the plates to move
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How are convection currents in the Earth created?
They are driven by heat released by natural radioactive processes / decay
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What are the disadvantages of convection currents?
Earthquakes / volcanic eruptions
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What is a plate boundary?
Where two tectonics meet
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Where do earthquakes and volcanoes happen?
Where tectonic plates meet
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What is continental drift?
Moving of the continents caused by convection currents
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What is Wegener's theory?
The idea that the plates were moving and that they were once together in a big landmass
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What was Wegener's evidence?
Continents seem to fit together / West coast of Africa and east coast of South America have the same rock patterns and types of plant/animal fossils > some which couldn't fly/swim so must've been joined together
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Why was the theory of continental drift not accepted for many years?
Wegener could not explain why the continents moved
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What proof is there of Wegener's theory?
Discovery of Mid-atlantic Ridge and detailed surveys of the Atlantic Ocean floor. Mid Atlantic ridge is a range of underwater mountains and volcanoes in the middle of the Atlantic Ocean
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How long have the proportions of gases in the atmosphere been the same?
200 million
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What are the proportions of gases in the atmosphere?
80% nitrogen / 20% oxygen / small % of other gases
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What happened in the first billion years of the earth's existence?
Volcanic activity
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What did the volcanic activity do?
Released gases and caused water to evaporate
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What happened over the next 2 billion years?
Bacteria / algae / plants evolved > algae and plants used up the carbon dioxide for photosynthesis and this released oxygen
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What produces the oxygen that is in our atmosphere?
Plants and algae
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What is the Miller-Urey theory?
Water / ammonia / methane and hydrogen sealed in a sterile flask / heated to evaporate water - water vapour / electric sparks to stimulate lightning / contents analysed and showed amino acids, the building blocks for proteins
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During the volcanic period, what is one theory regarding the atmosphere?
There was mainly Co2 and no o2
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Which gas makes up most of the atmosphere today?
Nitrogen (72%)
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Where is the carbon from Co2 now?
Locked up in sedimentary rocks as carbonates and fossil fuels / oceans
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What is the disadvantage of Co2 in oceans?
Impact on the marine life
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What happened when the Earth cooled?
The water vapour condensed to form oceans
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How is Co2 released into the atmosphere?
Plants and animals dying > fossil fuels burning > living things respiring
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How is Co2 removed from the atmosphere?
Plants photosynthesising > dissolved into oceans > locked up in sedimentary rock
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What is air?
A mixture of gases with different boiling points?
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How are raw materials taken from air?
Fractional distillation
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How does fractional distillation separate liquid air?
The air is cooled below -200 degrees and fed into the fractional distillation column > nitrogen is separated from oxygen and argon > further distillation is used to produce pure oxygen and argon
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