GCSE Chemistry C2

What does the lithosphere include?
The crust and upper part of the mantle. It is made up of tectonic plates. It is relatively cold and rigid
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What is the mantle?
The mantle is the solid section between the crust and the core. As you go deeper into the mantle the temperatures increase- it becomes less rigid and can flow slowly
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What is the core?
The inner core is solid, while the outer core is liquid
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What does radioactive decay create?
It creates a lot of heat inside the Earth, which creates convection currents in the mantle, which causes the plates of the lithosphere to move
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What causes volcanoes and earthquakes?
The movement of tectonic plates against each other
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Why is it difficult to study the inner structure of the Earth?
Because the crust is too thick to drill through
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How do scientists study the Earth's structure?
Using seismic waves, which are produced by earthquakes. By measuring the time it takes for these waves to travel through the Earth and where they are detected
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What are the two types of seismic waves?
P waves- travel through solids and liquids. S waves- travel through solids
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Discoveries about the Earth's structure?
S waves can travel through mantle, shows its solid. S waves not detected in the core, so outer core must be liquid. P waves travel faster through middle of core, which suggests inner core is solid
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What did Alfred Wegener hypothise?
That Africa and South America had previously been one continent which had then split
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What evidence did he provide for his theory?
Matching layers in the rocks on different continents, and similar earthworms living in both South America and South Africa
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Explain Wegener's theory of 'continental drift'?
300 million years ago there had been one supercontinent- Pangaea. Pangaea broke into smaller chunks which slowly drifted apart
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Why did people not accept his theory?
Wegener's explanation of how the 'drifting' happened wasn't convincing . He claimed that continents' moving could be caused by tidal forces and the Earth's rotation-but geologists showed that this was impossible
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What evidence was discovered in the 1960s?
They found evidence that magma rises up through the sea floor, solidifies and forms underwater mountains that are roughly symmetrical. This suggested that the sea floor was spreading
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What other evidence was discovered in the 1960s?
The magnetic orientation of the rocks. As the liquid magma erupts out of the gap, iron particles in the rocks tend to align themselves with the Earth's magnetic field, and as it cools it sets
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When do volcanoes occur?
When molten rock from the mantle emerges through the Earth's crust. Magma rises up and boils over
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What is subduction?
This is when a dense oceanic plate will be forced underneath a less dense continental plate, when the two plates collide
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How does subduction cause volcanoes?
Oceanic plate tends to be cooler at the edges of a tectonic plate, so the edges sink easily, pulling the oceanic plate down. As the oceanic crust is forced down it melts and starts to rise. Volcanoes form when this molten rock rises to the surface
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How is igneous rock formed?
When molten rock cools down and solidifies. The type of igneous rock depends on how quickly the magma cools and the composition of the magma
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What happens when the volcano produces magma that forms iron-rich basalt?
The lava from the eruption is runny and the eruption is fairly safe
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What happens when the volcano produces magma that forms silica-rich rhyolite?
The eruption is explosive. It produces thick lava which can be violently blown out of the top of the volcano
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Why do geologist study volcanoes?
To try and find out if there are signs that a volcanic eruption might happen . They study magma movement below the ground near to a volcano
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Why is it difficult for geologists to study volcanoes?
Volcanoes are very unpredictable
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How is sedimentary rock formed?
It is formed from layers of sediment laid down in lakes. Over time, the layers get buried under more layers and the weight pressing down squeezes out the water. Fluids flowing from pores deposit natural mineral cement
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How is limestone formed?
From seashells. It's mostly calcium carbonate and grey in colour. When it is heated it thermally decomposes to make calcium oxide and carbon dioxide
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How is metamorphic rock formed?
By the action of heat and pressure on sedimentary rocks over time. The mineral structure and texture may be different but the chemical composition is the same
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How is marble formed?
Marble is another form of calcium carbonate. Very high temperature and pressures break down the limestone and it reforms as small crystals. This gives marble a more even structure and makes it harder
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What do igneous rocks contain?
Different mineral in randomly arranged interlocking crystals-makes them hard.
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Where are aluminium and rock extracted from?
From ores in rocks. Rocks are a mixture of minerals. Ores are minerals we can get useful information from
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How is glass formed?
Heating up limestone with sand and soda until it melts. When the mixture cools it forms glass
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How is clay formed?
Clay is a mineral formed from weathered and decomposed rock. It's soft when its dug up, which makes its easy to mould into bricks
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How is clay hardened?
By firing at very high temperatures. Makes it ideal as a building material, bricks can withstand the weight of lots more bricks on top of them
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How is cement formed?
Clay contains aluminium and silicates. Powdered clay and powdered limestone are roasted in a rotating kiln to make a mixture of calcium and aluminium silicates- cement
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What happens when cement is mixed with water?
A slow chemical reaction takes place. This causes the cement to gradually set hard
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What is added to cement to make concrete?
Sand. Aggregate. Water. Concrete is a cheap and quick way of constructing buildings
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What is reinforced concrete?
It is a composite material. A combination of concrete and solid steel support. It is a better construction material as it combines the hardness of concrete with the flexibility and strength of steel
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What environmental damage does extracting rocks cause?
Quarrying uses up land and destroys habitats. Transporting rocks causes noise and pollution. Quarrying process produces dust and makes a lot of noise
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What does electrolysis of copper include?
'Splitting up with electricity'- passing a current through a piece of impure copper splits the pure copper off from the impurities
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What is the copper immersed into?
A liquid (the electrolyte) which conducts electricity. Electrolytes are usually free ions dissolved in water. Copper sulfate solution is the electrolyte used in purifying copper
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Explain the process of extracting pure copper?
It pulls electrons off copper atoms at the anode, causing them to go into solution. It then offers electrons at the cathode to nearby Cu2+ ions to turn them back into copper atoms. The impurities at the anode as sludge, pure copper at cathode
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What is the cathode?
The negative electrode. It starts as a thin piece of pure copper and more pure copper adds to it
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What is the anode?
The positive electrode. Is impure copper which will dissolve
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What results from the electrolysis of copper?
Copper dissolves away from the anode and it deposited to the cathode. The anode loses mass and the cathode gains mass
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Why is it cheaper to recycle copper than to mine and extract?
Recycling copper uses only 15% of the energy that'd be used to mine and extract the same amount
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Why can recycling copper be difficult?
It takes time and energy to sort out the copper from all the waste metal
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What is an alloy?
An alloy is a mixture of two or more different metals. It can also be a mixture of a metal and a non-metal. They often have properties that are different from the metals they are made from, and these properties make alloys more useful than pure metal
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What is steel an alloy of?
Iron and Carbon. Steel is harder and stronger than iron, as long as the amount of carbon does not increase from 1%. Iron on its own will rust, but steel is less likely to rust
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What is brass an alloy of?
Copper and Zinc. Brass is harder than copper and zinc, but shares other properties. It is used for making brass musical instruments
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What is bronze an alloy of?
Copper and Tin. Much harder and stronger than tin, more resistant to corrosion than either copper or tin. Bronze is used to make springs, bells and sculptures
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What is solder an alloy of?
Lead and Tin. It doesn't have a definite melting point, but gradually solidifies as it cools down
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What is amalgam an alloy of?
Mercury. It is used in dentistry for filling
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What is nitinol?
Alloys of nickel and titanium that have shape memory. They remember their original shape. This has increased the number of uses for alloys
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When does rusting occur?
When the iron is in contact with both oxygen and water. The chemical reaction that takes place when iron corrodes is an oxidation reaction
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What occurs when iron rusts?
The iron gains oxygen to form iron oxide. Water then becomes loosely bonded to the iron oxide and the result is hydrated iron oxide- rust
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How does rusting occur quickly?
Rust is a soft crumbly solid that soon flakes off to leave more iron available to rust again. If the water is salty or acidic, rusting will take place quicler
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Why doesn't aluminium corrode?
Aluminium reacts quickly with oxygen in the air to form aluminium oxide. A layer of aluminium oxide sticks to the aluminium below and stops further reactions taking place
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What advantages does aluminium have over steel?
Has a lower density so the car body of aluminium will be lighter. This gives the car better fuel economy, which saves fuel resources. It will corrode less, so will have longer lifetime
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What disadvantages does aluminium have over steel?
It costs a lot more than iron or steel, which is why car manufacturers tend to build cars out of steel instead
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What materials are needed to build cars?
Steel-strong-bodywork. Aluminium-strong, low density- parts of engine to reduce weight. Glass-transparent- windows. Plastics-light, hardwearing- internal covering for doors, electrical insulators for covering wires. Fibres- hardwearing- seats, floors
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Why is recycling cars important?
Save natural resources. Save money. Reduce landfill use
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Why is recycling car parts difficult?
It is time consuming to separate all non-metal bits of a car before they can be recycled
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What is the use of an universal indicator?
The dye in an indicator changes colour depending on the pH of a substance
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What is an acid?
An acid is a substance with a pH of less than 7. Acids form H+ ions in water. The pH of an acid is determined by the concentration of the H+ ions
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What is a base?
A base is a substance with a pH of greater than 7. An alkali is a base that is soluble in water
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What is neutralisation?
acid + base -> salt + water
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What are the three main essential elements in fertilisers?
Nitrogen. Phosphorus. Potassium. If plants don't get enough of these elements, their growth and life processes are affected. They can be used up by a previous crop
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What do fertilisers do?
They replace these missing elements or provide more of them. This helps to increase crop yield, as the crops grow faster and bigger. The fertiliser must be dissolved in water so it can be taken in by crop roots
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How is ammonium nitrate formed?
If you neutralise nitric acid with ammonia. This is an especially good fertiliser as it has nitrogen from two sources
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How is ammonium sulfate formed?
By neutralising sulfuric acid with ammonia. Can be used as fertiliser
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How is potassium nitrate formed?
By neutralising nitric acid with potassium hydroxide. Is also a fertiliser
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What problems can fertilisers cause?
They pollute water supplies and cause eutrophication
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Explain the process of eutrophication?
When fertiliser is put on fields some of it runs off and finds its way into rivers. The level of nitrates and phosphates in the river water increases. Algae living in the river use the nutrients to multiply rapidly, creating an algal bloom
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Explain the process of eutrophication?
The algal bloom blocks off light to the river plants below. The plants cannot photosynthesise, so have no food and die. Aerobic bacteria feed on dead plants and start to multiply. As they multiply they use up oxygen in water. Organisms in river die
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Explain the process of preparing ammonium nitrate?
Add methyl orange indicator to the ammonia. Add nitric acid into ammonia until colour changes from yellow to red. This colour changes indicates that ammonia has been neutralised. Evaporate the solution. Leave to crystallise
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What is meant by the yield of a reaction?
The mass of product that you end up with
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What is the predicted yield of a reaction?
The amount of product that you would get if all the reactant was converted into product
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What is the Haber Process?
It takes nitrogen and hydrogen gas and makes ammonia. Its names after Fritz Haber. Important industrial process because the ammonia is needed for fertilisers. It is a reversible reaction
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Where does the nitrogen and hydrogen come from?
Nitrogen is obtained from the air. Hydrogen comes from the cracking of oil fractions or natural gas
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Why won't all the nitrogen and hydrogen convert to ammonia?
Because the reaction is reversible. The N2 and H2 which don't react are recycled and passed through again so none is wasted
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What industrial conditions are needed for the Haber Process?
Pressure: 200 atmospheres. Temperature:450*C. Catalyst:Iron
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What does high pressures favouring the forward reaction result in?
Pressure being set at 200 atmospheres. This high pressure increases the percentage yield of ammonia
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What does high temperatures favouring the reverse reaction result in?
High temperatures decrease the percentage yield of ammonia
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What problem does using low temperatures cause manufacturers?
Slower reaction rate. So manufacturers use high temperatures anyway, to increase the rate
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How does the iron catalyst impact the process?
It makes the reaction go faster, which gets it to the equilibrium properties quicker. It keeps costs down as without the catalyst the temperature would have to be raised further to get a quick enough reaction, and this would reduce yield
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What does production costs depend on?
Price of energy. Costs of Raw Material. Labour Costs. Plant Costs. Rate of Production
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How are optimum conditions chosen?
They are chosen to give the lowest production cost per kg of product
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Where is salt extracted from in Britain?
From underneath deposits left millions of years ago when ancient seas evaporated. There are huge deposits of this rock salt under Cheshire
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What is rock salt?
It is a mixture of salt and impurities. It's drilled, blasted and dug out and brought to the surface using machinery
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How can rock salt also be mined?
By pumping hot water underground. The salt dissolves and the salt solution is forced to the surface by the pressure of the water- solution mining
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What is subsidence?
Filling in the holes in the ground after mining. If not the land could collapse and slide into the holes- which is subsidence
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How can rock salt be used?
In its raw state on roads to stop ice forming, or the salt can be separated out and used to preserve or enhance the flavour in food or for making chemicals.
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How is concentrated brine electrolysed industrially?
The electrodes are made of an inert material-this is so they won't react with the electrolyte or the products of the electroylsis
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What happens at the cathode?
Two hydrogen ions accept one electron each to become one hydrogen molecule- REDUCTION
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What happens at the anode?
Two chloride ions lose one electron each to become one chlorine molecule- OXIDATION
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What useful products are formed?
Hydrogen gas is given off at the cathode. Chlorine gas is given off at the anode. Sodium Hydroxide is formed from the ions left in solution
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What is the hydrogen gas used for?
Hydrogen gas is used to make ammonia and margarine
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What is the chlorine gas used for?
Chlorine is used to disinfect water, to make plastics, solvents or hydrochloric acid
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What is the sodium hydroxide used for?
Sodium hydroxide is used to make soap, or can be reacted with chlorine to make household bleach
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Other cards in this set

Card 2


What is the mantle?


The mantle is the solid section between the crust and the core. As you go deeper into the mantle the temperatures increase- it becomes less rigid and can flow slowly

Card 3


What is the core?


Preview of the front of card 3

Card 4


What does radioactive decay create?


Preview of the front of card 4

Card 5


What causes volcanoes and earthquakes?


Preview of the front of card 5
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