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103 Cards in this Set
- Front
- Back
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Describe the structure of an atom: |
Tiny nucleus in the middle containing protons and neutrons- positively charged nucleus Sea of free electrons in shells |
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What are the charges and relative masses of the particles in an atom? |
Particle Charge Mass Proton +1 1 Neutron 0 1 Electron -1 1/2000 |
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What is the relationship between protons and electrons? |
No. of protons = No. of electrons |
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What is an element? |
A substance with only one type of atom All of one element have the same number of protons |
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What do all elements in one group have in common (in the periodic table) ? |
They all have the same number of electrons in their outermost shell |
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What do all the elements in one period have in common? |
They all the the same number of electron shells |
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What is the mass number? |
The combined number of protons and neutrons |
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What is the atomic number? |
The number of protons in an element ( and subsidently the number of electrons) |
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How do you work out the number of neutrons? |
Mass number - atomic number |
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How are the electrons organised? |
They are organised in shells and the lowest energy levels nearest the nucleus are filled first 1st shell - 2 electrons 2nd and 3rd- 8 electrons |
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Why do atoms want to react? |
To gain a full outer shell of electrons so they re un-reactive |
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Why are the noble gases stable? |
They are un-reactive as they have a full outer shell of electrons |
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Explain how ionic bonding works: |
A non-metal and a metal bond as the metal atom loses electrons to form positive ions and the non-metal atom gains electrons to form negative ions - to fill their outer shells These opposite charges are then attracted to each other |
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Explain how covalent bonding works: |
Non-metals bond together by sharing electrons to fill up their outer shell They then form molecules with shared pairs of electrons forming covalent bond |
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What does the law of conservation of mass mean? |
That atoms aren't lost or gained in a chemical reaction Therefore there must be the same number of atoms of both sides of the equation |
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What is limestone? |
Limestone is quarried out of the ground and it used for building it is mainly calcium carbonate ( CaCO3) |
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What is the limecycle? |
Limestone is thermally decomposed to form Calcium oxide and carbon dioxide Water is then added to form calcium hydroxide More carbon dioxide is then added to form calcium carbonate again and water |
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How do you make cement? |
You use limestone and powdered clay |
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How do you make mortar? |
You mix cement with water and sane |
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How do you make concrete ? |
You mix cement with sand and aggregate |
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What are the advantages of using limestone as a product |
It is widely available and cheap to buy It is hardwearing but still looks attractive It is quick and cheap to build with It doesn't rot when wet It sit ire resistant and can't be corroded |
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What are the advantages of quarrying limestone? |
It can provide jobs for people and boost the local economy It can also lead to improvements locally with transport, roads and recreation facilities Afterwards it can be made into a lake for wildlife |
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What are the disadvantages of quarrying limestone |
It can create noise pollution for the locals It can create dust which can cause breathing problems Energy needed comes from burning fossil fuels which realises carbon dioxide Destroys habitats of animals Permanently destroys land- visual pollution |
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What can limestone be used for? |
Houses, roads Chemicals in it can be used to make dyes, paint and medicines Can neutralise acidic soil, and acidic lakes + river |
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What is an ore? |
A rock which contains enough metal to make it worthwhile extracting. In many places it is extracted as an oxide |
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Why are low grade ore now extracted? |
As we are running out of high grade ores and the need for the metals is still very high |
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What are the stages of extraction of a metal? |
Mine ---> Concentrate ---> extract ---> purify |
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When is reduction used to extract a metal? |
When the metal is below carbon in reactivity Carbon is added and this removes the oxygen from the ore and forms the pure metal and carbon dioxide |
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When is electrolysis used to extract a metal? |
When the metal is more reactive than carbon This is more expensive as energy is needed to make the ore molten and for the electricity |
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What is a native metal? |
A metal which when quarried is not combined with anything else |
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How is copper extracted? |
Copper is reduced with carbon and then smelted in a furnace Electrolysis is then used to purify it The copper ions near the cathode gain electrons and become copper atoms |
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How are load grade ores extracted (copper)? |
Bio-leaching or Phytomining |
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What is bio-leaching? |
When bacteria feed on copper compounds and this produces copper solution which cane then be displaced or electrolysed
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What is phytomining? |
When plants are grown on copper soil, the copper ions then absorb the ions and accumulate in the leaves
When the leaves are burnt copper oxide is produced Then this is reacted with sulphuric acid which creates copper sulphate solution which can be purified using electrolysis or displacement |
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In displacement why is scrap iron sometimes used? |
It is very cheap and is more reactive than copper |
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How is iron extracted? |
In a blast furnace cast iron is formed which has some carbon in it and is very brittle. The cast iron in then reacted with oxygen to produce sure iron |
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What is steel used for? |
Stainless - cutlery and hospital instruments Low carbon = car bodies High carbon = blades for cutting tools and bridges |
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What are the types of steel? |
Steel is an alloy Stainless- easy to clean, doesn't corrode Low carbon - easily shaped High carbon - very hard |
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What are the pros and cons on metal extraction? |
Pros Useful products made Boosts local economy and creates jobs Cons Causes noise and visual pollution Can be dangerous is abandoned |
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Why is recycling metal important? |
Fossil fuels are running out - need to conserve them- burning also leads to acid rain, global dimming and climate change Less stages so less energy than to extract again Landfills takes up space and pollute the area |
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What are the properties of transition metals? |
They are the typical metals they are good conductors of heat and electricity They are malleable and strong |
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Use of titanium? |
It is un-reactive, strong, has a high melting point, low density and is resistant to corrosion Therefore it can be used as artificial hips |
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Why is titanium expensive? |
Once reacted with carbon it is too brittle so it has to be reacted with chlorine and then magnesium and sodium. The electrolysis of these metals is expensive and there are also lots of stages |
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Use of aluminium? |
It is light weight, strong, resistant to corrosion, low density, un-reactive,good conductor of heat and electricity, ductile and malleable It is used in planes |
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Use of copper? |
It is a good conductor of heat and electricity, it is malleable and un-reactive Used as water pipes and electricity wires |
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What is an alloy? |
A mixture of different metals |
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Why are alloys stronger than pure metals? |
They include different sized atoms so the layers are distorted an they can't as easily slide over each other |
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Give some example of alloys |
Bronze- copper + tin (medals and statues) Gold alloys - used to make jewellery Aluminium alloys - used to make aircraft |
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What is crude oil? |
A picture of hydrocarbons Hydrocarbons are compounds made of just carbon and hydrogen |
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How does a fractionating column work? |
Crude oil is pumped in the bottom and the vaporised oil rises up the column and it tapped off at different levels when it condenses. |
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What is an alkane? |
A saturated hydrocarbon with chains of carbon atoms surrounded by hydrogen atoms |
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What is the formula for an alkane? |
CnH2n+2 |
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What are the trends for molecules from crude oil? |
The shorter the molecule - the less viscous II - the more flammable II - the more volatile volatile = turns into a gas at a lower temperature |
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What are the different uses of hydrocarbons? |
The refinery gas is used as bottled gas as it has the lowest boiling point The petrol fraction has a high boiling point so it easily stood in a car and ignited Viscous hydrocarbons are used for covering road |
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Pros of using crude oil as a fuel? |
Often cheapest and easiest fuel to use More reliable as doesn't rely on earth conditions |
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Cons of using crude oil as a fuel? |
Non-renewable so will run out Oil spills cause poison organisms such as birds and other marine organisms Burning oil causes global warming, acid rain and global dimming |
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How is sulphur dioxide produced? |
When the fuel is burnt such as crude oil, if the fuel has sulphur impurities sulphur dioxide is released. |
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What is produced when fuel is burnt if it incomplete combustion occurs? |
Carbon monoxide which is a poisonous gas |
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What affect does sulphur dioxide have on the environment? |
It reacts with the clouds to form dilute sulphuric acid which falls as acid rain This causes lakes to become acidic and kills trees, as well as damaging buildings |
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How to rescue acid rain? |
Use low sulphur fuels Reduce use of fossil fuels |
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What are the effects of global warming? |
Carbon dioxide leads to global warming which leads to the ice caps melting and flooding and many other problems |
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What are the effects of global dimming? |
Global dimming is caused by particles of soot and ash from burning fossil fuels Global dimming reflects sunlight back into space |
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What are alternative duels which are renewable? |
Ethanol Biodiesel Hydrogen gas |
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What are the pros and cons to ethanol |
Ethanol is produced from plant material and the fermentation of plants Pro It is carbon neutral as the plants photo synth.. Cons It isn't widely available Increase food prices- land is used Engines have to be converted |
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What are the pros and cons to biodiesel? |
Produced from vegetable oils Pros It is carbon neutral Less sulphur dioxide made Engines don't have to be converted Cons Expensive to make and could also increase food prices, also hard to make |
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What are the pros and cons to hydrogen gas? |
It is made form he electrolysis of water Pros It is very clean only produces water Cons Need special expensive engine Hard to store |
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What is cracking? |
= Breaking down long hydrocarbon chains into smaller more useful chains |
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How does cracking occur? |
Cracking is thermal decomposition The hydrocarbon chain is vaporised with heat Then the vapour is passed over a powdered catalyst of aluminium oxide at around 400-700 oC |
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What are the products of cracking?
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Most of the product are alkanes and some alkenes this is used to form products such as ethene |
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What is an alkene? |
= An unsaturated hydrocarbon with a double bond |
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What is the formula for an alkene? |
CnH2n |
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How do you test for an alkene? |
Use bromine water and alkene will make the water go colourless and the double bond will open and bond with the bromine |
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How is ethanol produced? |
Ethene is reacted with steam with a catalyst to make ethanol It is cheap, however ethene is from crude oil so is non-renewable so it will become very expensive |
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How does fermentation occur? |
Sugar is converted into carbon dioxide and ethanol with a low temperature The raw material is renewable, and it is cheap Although it isn't very concentrated and needs to be purified |
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What is polymerisation? |
Joining together lots of small alkene molecules to form long chain molecules (polymers) |
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How do you change the physical properties of a polymer? |
Change what monomers it is made of Change the conditions used to make it the temperature and the pressure |
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What are the different uses of polymers? |
Light stretchable polymers are used to make plastic bags and tights Dental polymers- used in resin in fillings Polymer- used as smart material with memory foam mattresses |
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Why are polymers hard to recycle? |
They aren't biodegradable so they aren't broken down by micro-organisms |
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How is oil extracted from a plant? |
The material is crushed Then it is pressed between metal plates Then it is distilled to remove impurities |
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Why re vegetable oils used in food? |
They have very high energy They have nutrients such as vitamins They have essential fatty acids |
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Why are vegetable oils good for cooking? |
They have high boiling points than water They give food a different flavour They increase the energy content of the food |
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How can vegetable oils be used to make fuels? |
They can be processed to make fuels such as biodiesel as they have a lot of energy so are suitable as fuels |
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What are the characteristics of unsaturated oils? |
They contain long-chain molecules with double bonds They de-colourise bromine water- alkenes Liquid at room temperature |
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What is hydrogenation? |
When hydrogen is reacted with unsaturated oils with a nickel catalyst at 60oC. |
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What are the properties of hydrogenated oils? |
They have higher melting points- spreadable They are cheaper and keep longer Partially hydrogenated have lots of trans fats which are bad for you. |
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Which are healthier saturated or unsaturated fats? |
Unsaturated fats are healthier as saturated fats increase cholesterol in you blood blocking up arteries and increasing the risk of heart disease Natural unsaturatedjfats reduce blood cholesterol |
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Why are emulsifiers used? |
So that two miscible liquids can be mixed as the emulsifier molecule has a hydrophilic head and a hydrophobic tail Therefore the emulsifier surrounds the oil droplets so the emulsion won't separate |
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What re the properties of emulsions? |
Thicker, and better at coating foods They have a softer texture, they can also be used in moisturising lotions to make it easier to rub well into skin. |
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What are the pros and cons on emulsions? |
Pros Gives emulsions a long shelf life Lower in fat with a good texture Con Many people are allergic to emulsifiers |
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How did people used to think mountains were formed? |
They believed as the earth sued to be very hot, that when it cooled down the wrinkles formed mountains However the negatives of this are that if it were true the earth would still be shrinking and there would be mountains everywhere. |
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What is Wegner's theory of continental drift? |
He said that 300 million years ago there was one supercontinent Pangea and that eventually the contents drifted apart to form our world today |
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What proof did Wegner have? |
Similar fossils were found on different continent South America and Africa seem to fit together like a jigsaw Similar animals were found on different continents |
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Why didn't people accept Wegner's theory? |
There were simpler explanations such as land bridges that don't still occur He didn't have an explanation as to why it happened There wasn't enough proof (only a few cm move each year) |
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What is the structure of the earth? |
The crust is the top and thinnest layer- solid The mantle is solid but moves like a liquid The outer and inner core combined are the thickest layer |
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What are the tectonic plates? |
Slabs of earth made up of the crust and upper mantle |
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Why do the tectonic plates move? |
Convection currents in the mantle are caused by radioactive processes releasing heat These convection currents move the tectonic plates a few cm each year Volcanoes and earthquakes occur at plate boundaries |
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Why can't scientists predict earthquakes and volcanic eruptions? |
They can't see what is happening in the mantle Don't want to evacuate people for no reason Don't know their strength They are sometimes wrong |
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How are gases separated from the air? |
Filtered- to remove impurities Cooled to - 200 and water and carbon dioxide is removes as a solid so not to block the pipes All liquids going into fractionating column Nitrogen goes first and then argon and oxygen are further distilled |
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What gases were there in the early atmosphere? |
Carbon dioxide Methane trace Ammonia trace Water vapour However as the earth cooled the water vapour condensed and fell as rain forming oceans |
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How was Carbon dioxide removed from the early atmosphere? |
Absorbed into eh ocean Formed rocks Fossil duels Photosynthesis - oxygen increased Sea creatures shells |
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How was nitrogen introduced into the atmosphere? |
Ammonia and Oxygen reacted to form nitrogen gas |
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What is the Muller-Urey Primordial Soup theory? |
As amino acid are the building blocks of proteins they must have been created uses the gases and conditions int eh early atmosphere So some scientists uses specific gases and lightening and after a few weeks formed amino acids |
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What were the problems with the Muller-Urey experiment? |
No-one can be sure the gases were all present Could have been extra gases- not specifically chosen Might not have had continuous lightening |
