Chemistry Module 2

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List all parts of the Earth's structure
Crust / Lithosphere / Mantle / Outer Core / Inner Core
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Tectonic Plates float because...
they are less dense than the mantle
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Why is it difficult to study the Earth's structure?
Scientists cannot get to the structure directly as the crust is too thick to drill through
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What are the two types of seismic wave and what can they travel through?
P waves - they can travel through solids and liquids / S waves - they can only travel through solids
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How can we study Earth's inner structure?
Scientists use seismic waves which can be produced by man made explosions or by earthquakes. They then measure the time it takes for the waves to travel through Earth and see where they are detected and amek
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What were previous theories about Earth's structure?
They used to think the continents were connected with land bridges which had been sunk or covered by water as they Earth cooled
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Explain Wegener's theory of continental drift
Alfred Wegener hypothesised that Africa and South America used to be one continent. He found matching layers of rock on both continents. He thought all continents used to be one but were drifting apart over millions of years - plate tectonics
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Why wasn't the continental drift theory accepted at first?
Wegener's theory didn't explain how the drifting happened / the movement wasn't detectable / Wegener thought the movement of the continents was due to tidal forces and Earth's rotation but this was proved to be false by geologists
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What evidence supports Wegener's theory?
Scientists found magma rising up through the sea floor at the mid-Atlantic ridge. The mountains were almost symmetrical each side.This showed the sea floor was spreading and so the continents were moving apart
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What is the difference between magma and lava?
Molten rock below Earth's surface is magma but above Earth's surface it is lava
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Explain how volcanoes are formed and how explosions occur
When oceanic and continental plates collide, the oceanic plate is forced under the continent (as it is denser). The heat from the planet then melts the edges and magma starts to rise. If magma finds a way to the surface volcanoes are formed
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Igneous rock can vary depending on...
how quickly the magma cools / the composition of the magma
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How can volcanic eruptions vary?
If the magma forms iron-rich basalt, then the lava from the eruption is runny and so the explosion is fairly safe. If the magma forms silica-rich basalt, then the lava is thick and the eruption can be explosive
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How can geologists predict volcanic eruptions?
They monitor magma movement below the ground near to a volcano
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How does sedimentary rock form? Give an example
They are formed when layers of sediment are laid down. Over millions of years the layers get buried and the weight squeezes out any water. Fluids flowing through pores deposit mineral cement e.g Limestone
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How does metamorphic rock form? Give an example
They are formed when heat and pressure is applied to sedimentary rocks over long periods of time. The mineral structure and texture is now different making it harder e.g marble
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How does igneous rock form? Give an example
When magma rises to the surface and cools. It is hard because it contains various different minerals in randomly arranged interlocking crystals e.g Granite
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How is glass made?
Heat up sand, limestone and soda together until it melts. When it cools, it is glass
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How are bricks made?
Clay is dug up from weathered and decomposed rock. It's then moulded into bricks. It is then hardened by firing at high temperatures. Bricks can withstand a lot of weight.
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How do you make cement?
Powdered clay and limestone are roasted in a kiln to make a mixture of calcium and aluminium silicates. When water is added the cement gradually hardens. If sand, aggregate and water are added, it forms concrete.
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What are the problems with extracting rocks?
It uses up land and destroys habitats / transporting rock can cause noise and pollution / quarrying produces a lot of dust and noise / Disused sites are dangerous, they can collapse and people can drown
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How can electrolysis be used to obtain pure copper?
By putting pure copper at the cathode and impure copper at the anode, copper dissolves into solution forming Cu2+. Any impurities fall off. The ions are then attracted to the cathode forming pure copper once again.
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What are the advantages of recycling copper?
It is cheaper than digging for new copper / Recycling uses only 15% of the energy needed to mine and extract the same amount
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What does it mean if a metal is native?
It means it is found unreacted in the ground
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List the ways you can extract metal from their ores
Burn them with carbon / Use electrolysis
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What is an alloy?
A mixture of two or more different metals
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What is so great about steel?
It is harder than iron / Stronger than iron (as long as the amount of carbon does not increase past 1%) / Steel is less likely to rust than iron
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List other alloys, what they're made of and their uses
Brass - zinc and copper - musical instruments, fixtures and fitting / Bronze - copper and tin - used to solder / Amalgram - contains mercury - fillings for dentistry
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Give an example of a smart alloy
Nitinol - Nickel and titanium - has shape memory
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Give the advantages of using aluminium as a car body
Lower density means the car will be lighter so much better fuel econmoy and saves resources / Aluminium corrodes less, longer lifetime
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Why do car manufacturers use iron or steel for the car body?
They are cheaper than aluminium
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List the materials needed for a car
Steel - bodywork / Aluminium - parts of engine / Glass - windows and windscreens / PLastic - internal coverings for doors, dashboards etc / Fibres - seats and floor
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Why is it important to recycle cars?
Save money / Save natural resources / Reduce landfill use
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What is the definition of an acid?
A substance with a pH less than 7. Acids form H+ ions in water - pH is determined by concentration of the H+ ions
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What is the definition of an base?
A substance with a pH higher than 7. An alkali is a base that is soluble in water. Alkalis form OH- ions in water
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What are fertilisers used for?
To improve plant growth and replace lost nutrients in the soil
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Name an element found in fertilisers and how is it needed?
Nitrogen - proteins for leaves and stalks / Phosphorus - speeds up the growth of roots and ripening of fruit / Potassium - protects against disease and frost, promotes seed growth
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What is percentage yield?
The mass of product that you end up with is called the yield of a reaction
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Why don't you get a 100% yield?
Not all of the reactant will be converted to product
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What is the reversible reaction of the Haber Process?
N2 + 3H2 = (reversible sign) 2NH3
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Where do the element come from?
Nitrogen comes from the air (78% of air is N2) Hydrogen comes from cracking of oil fractions or natural gas
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Why is 450*C used in the Haber Process?
It is a compromise temperature as it is low but not too low so that the particles don't move too slowly to react however, high temperatures favour the backward reaction. 450*C is a compromise
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Why is an iron catalyst used in the Haber Process?
Without a catalyst, the particles would move too slowly and so virtually no reaction happens in any sensible time. The catalyst doesn't increase percentage yield, it only speeds up the reaction.
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Why is 200atm used in the Haber Process?
Higher pressures favour the forward reaction. However, if the pressure is too high, the cost of the equipment and generating it exceeds the price you get from the extra ammonia produced. 200 is a compromise.
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What happens in the Haber Process?
Nitrogen and hydrogen are put in a reaction chamber together in the ratio 1:3. With the set conditions, ammonia is formed. The gass is sent to a condensing chamber where it si cooled to a liquid and taken away. Any unreacted gas is recycled.
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What effects production cost?
Price of Energy / Cost of Raw Material / Labour Costs / Plant Costs (Equipment) / Rate of Production
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How do countries get salt?
Hot countries evaporate sea water. Cold countries have to extract salt from underground deposites
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What problems are caused by solution mining?
The holes in the ground could lead to the land collapsing and sliding into the holes - subsidence
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Electrolysis of brine gives off what products?
Sodium Hydroxide, Hydrogen gas and Chlorine gas
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What can the products from the electrolysis of brine be used for?
H2- haber process and margarine / Cl2 - disinfectant for water, make plastics, solvents and hydrochloric acid / NaOH - soap or can react with chlorine to make bleach
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Other cards in this set

Card 2

Front

Tectonic Plates float because...

Back

they are less dense than the mantle

Card 3

Front

Why is it difficult to study the Earth's structure?

Back

Preview of the front of card 3

Card 4

Front

What are the two types of seismic wave and what can they travel through?

Back

Preview of the front of card 4

Card 5

Front

How can we study Earth's inner structure?

Back

Preview of the front of card 5
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