Download C2 Key Facts Sheet - North Leamington School

C2 Key facts sheet: Higher.
A What is the Earth’s structure?
The Earth is made of a central iron Core, molten Mantle, and thin outer Red
Crust (a layer of rock.)
The lithosphere is made up of the outer layer of the mantle, and the
crust.
The crust is less dense than the mantle and so floats on top of it.
The crust is made up of Tectonic plates. These are rocky rafts that
float on the mantle Continental plates = found above the sea.
Oceanic plates = found below the sea.
Radioactive decay inside the Earth creates heat. This heat creates
Convection Currents, which make the plates move.
Volcanoes and earthquakes occur where plates meet.
The oceanic plate is more dense and cooler at the ocean point so it
sinks beneath the continental plate, where it melts = subduction.
What are volcanoes?
Volcanoes are made when an oceanic plate collides with a continental
plate.
The oceanic plate sinks below the continental plate forming a volcano.
When a Volcano erupts the molten magma comes up from the mantle
because it is less dense than the surrounding rock.
Magma = liquid rock in the magma.
Lava = liquid rock that comes out of a volcano.
Safe volcanoes produce runny lava = iron-rich basalt.
Dangerous volcanoes produce thick lava that has gases dissolved in it
= silica-rich ryolite.
When the lava cools slowly the igneous rock formed has large
crystals.
When the lava cools quickly the igneous rock formed has small
crystals.
People live near volcanoes because the land is more fertile.
Geologist study volcanoes so they can try to predict when there will
be an eruption, and to find out more about the structure of the Earth.
They also study earthquakes as the shock waves produced tell us
about the structure of the Earth.
It’s difficult to study the inner structure of the Earth because the
crust is too thick to drill through.
Many ideas have been put forward to explain the Earth’s surface. The
theory of plate techtonics is now accepted because there is a lot of
evidence to support it, and many scientists have discussed and tested
it.
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C2 Key facts sheet: Higher.
B Where do building materials come from?
Mining or quarrying rocks for use in buildings damages the landscape
and causes dust.
Aluminium and iron come from ores (the metal is joined to other
elements e.g. Aluminium Oxide.)
Bricks are made from clay.
Glass is made from sand.
Granite and marble are stronger than limestone.
Granite is igneous rock and is made when lava from volcanoes cools.
Limestone is sedimentary rock and is made when the shells of dead
sea creatures are compressed together.
Marble is metamorphic rock and is made when by the action of heat
and pressure on limestone.
Limestone and marble are both forms of calcium carbonate
Thermal decomposition is when heat breaks a material down.
Heat breaks Calcium Carbonate into Calcium Oxide and Carbon Dioxide
Calcium Carbonate
Calcium Oxide + Carbon Dioxide
CaCO3
CaO
+ CO2
Cement is made when limestone and clay are heater together.
Concrete is made from cement, sand, aggregate and water.
Concrete can be reinforced with steel rods = composite material.
This material combines the hardness of concrete with the flexibility
and strength of steel.
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C How can we extract metals from the Earth and make them more useful?
Copper can be extracted by heating copper ore with carbon.
This process is called reduction because it removes oxygen from a
substance.
Copper can be purified by electrolysis.
Recycling copper us cheaper than extracting copper from its ore
because it saves money and uses less energy.
Cathode (-)
pure
copper.Gains
mass as pure
copper is
Anode (+) impure
copper. Loses mass as
copper dissolves.
Copper (II)
sulphate
electrolyte
Anode: Copper atoms lose electrons to make copper ions = oxidation.
Cu - 2e- → Cu2+
Cathode: Copper ions gain electrons to make copper atoms =
reduction.
Cu2+ +2e- Cu
Alloys are mixtures containing one or more metal elements.
Brass, bronze, solder, steel and amalgam are alloys.
Amalgum is used in tooth fillings.
Brass is used in musical instruments, coins and door knockers.
Solder is used to join electrical wires.
The metals in alloys have different properties to individual metals that
are in them.
Steel is an alloy made of iron and carbon.
The carbon makes the steel less likely to rust, and stronger than iron.
Making an alloy of a metal can change the original metal’s hardness,
density, boiling point and strength.
Amalgam contains mercury as its main metal.
Brass contains copper as its main metal.
Solder contains lead and tin as its main metals.
Smart alloys have an increased number of uses:
Nitinol (nickel and titanium) are used to make frames for glasses
because they have shape memory = can return to their original shape
after bending.
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D What should we make cars of?
Iron v Aluminium
Iron is more dense than Aluminium.
Iron is magnetic; Aluminium isn’t magnetic.
Iron corrodes more easily than Aluminium.
Both Iron and Aluminium are malleable = can be shaped.
Both Iron and Aluminium conduct electricity.
Cars are made of steel because it is strong and cheap (car body ),
copper because it is a good conductor of electricity (electrical wiring),
aluminium because it is light (engine), glass because it is transparent
(windows), plastics because it is hardwearing (dash board), fibres
because they are hard wearing and soft (seats and carpet.)
Aluminium makes a lighter car body so it uses less fuel (better fuel
economy) and corrodes less (has a longer lifetime.)
BUT Aluminium is expensive.
Recycling Steel and Aluminium saves natural resources and reduces
disposal problems.
Iron corrodes to produce the chemical rust = hydrated iron(III) oxide
Water and oxygen make iron rust.
Corrosion, including rusting, involves oxygen being added to a metal =
oxidation.
Iron + oxygen + water
iron (III) oxide
Sea water speeds up the rusting process because it contains salt.
Acid also speeds up the process of rusting.
Aluminium doesn’t corrode as much as iron.
Aluminium reacts with oxygen and water to form a protective layer of
Aluminium Oxide.
Iron Oxide is porous, so oxygen and water can penetrate lower layers,
making the Iron Oxide flaky.
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E How can we make fertiliser?
Ammonia is made from Hydrogen and Nitrogen = The Haber Process
Nitrogen comes from air and Hydrogen comes from cracking oil
fractions from natural gas.
Making Ammonia is a reversible reaction = the reaction goes in both
directions = products are made, but they can reform the reactants
This is a reversible reaction sign.
The conditions for making ammonia are:
- Iron catalyst
- High pressure 250atm
- Temperature of 450oC
Unreacted Nitrogen and Hydrogen are recycled.
These conditions are the optimum conditions used to give a sufficient
daily yield of product.
A low percentage yield is accepted because the reaction can be
repeated many times by recycling the reactants.
Increasing the temperature reduces the amount of Ammonia produced
but if the temperature was lower than 450oC the reaction would be too
slow.
Increasing the pressure increases the amount of Ammonia produced
but it is too expensive to reinforce the equipment for a pressure
higher than 200atm to be used.
Optimum conditions give the lowest cost rather than the fastest
reactions or the highest percentage yield.
Nitrogen + Hydrogen
Ammonia
N2
+ 3H2
2NH3
The cost of making a new substance depends on:
- The price of electricity.
- The cost of the starting materials e.g. Nitrogen and Hydrogen
- The wages of the workers
- The equipment needed
- The cost of the catalyst and how quickly the product can be
made.
Different factors affect the cost of making a new substance:
- The higher the temperature the higher the energy cost.
- The higher the pressure the higher the plant cost.
- Catalysts reduce the costs by increasing the rate of reaction.
- Recycling unreacted starting materials reduces the cost.
- Automation (using machines rather than workers) reduces wages bills.
Ammonia is used to make fertilisers so that more food can be made to
Ammonia is also used to make Nitric Acid.
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F How does pH change during neutralisation reactions and what salts are made?
Indicators:
Universal Indicator changes colour in acids and alkalis.
Universal Indicator can be used to estimate the pH of a solution.
Some indicators can show a sudden colour change
e.g. litmus turn is red in acid, and blue in alkali
Some indicators show a gradual colour change
e.g. Universal Indicator
All acids contain H+ ions
e.g. HCl = Hydrochloric acid; H2SO4 = Sulfuric acid, HNO3 = Nitric acid
The more concentrated the acid the more H+ ions there are and the
lower the pH number is.
Bases and alkalis are the opposite of acids.
Bases are insoluble solids e.g. metal oxides and some metal
carbonates.
Alkalis are bases which are soluble (dissolve in water) so are always
solutions. They produce OH- ions = metal hydroxides and some metal
carbonates.
Acids can neutralise alkalis.
Alkalis can neutralise alkalis.
Neutralisation involves the reaction:
H+ + OHH2O
Neutralisation:
Acid + Base
Salt + Water
Acid +Alkali
Salt + Water
Acid + Carbonate
Salt + Water + Carbon Dioxide
Carbon dioxide turns limewater cloudy.
The name of a salt is made up of the name of the metal in the alkali,
and the acid used:
Hydrochloric acid = metal chloride
Sulfuric acid = metal sulfate
Nitric acid = metal nitrate
e.g. sodium oxide + hydrochloric acid
sodium chloride + water
(salt)
calcium hydroxide + sulfuric
calcium sulfate + water
acid
(salt)
If ammonia is used as an alkali:
Ammonia
+ nitric acid
ammonium
+ water
nitrate
(salt)
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G Why do we need fertilisers?
Fertilisers increase crop yield (produce more crops) by:
- Replacing essential elements used by a previous crop,
- Providing additional essential elements,
- Providing more nitrogen to increase growth.
Plants absorb minerals through their roots so fertilisers must be
dissolves in water.
Fertilisers provide essential chemical elements e.g. nitrogen N,
phosphorous P, and potassium K, which are needed for plant growth.
Advantages of using fertilisers = more crops to help feed the
increasing world population.
Disadvantage of using fertilisers = death of aquatic life (plants and
animals that live in lakes and rivers) as fertilisers are washed into
rivers and lakes.
Eutrophication :
- Rain water washes excess fertiliser off the fields.
- This increases the nitrate/phosphate levels in rivers.
- This causes algae to bloom (grow uncontrollably.)
- This blocks off sunlight to other plants which die.
- Aerobic bacteria thrive and use up the oxygen.
- This causes most fish and other aquatic animals to die.
To prepare a fertiliser in a lab you need to:
- Fill a burette (long, thin glass tube) with an acid.
- Measure some alkali using a measuring cylinder and add it to a
conical flask.
- Add some indicator.
- Titrate (allow the acid to run from the burette into the alkali in
the conical flask until the indicator shows the alkali has been
neutralised.
- Evaporate off the excess water but don’t boil dry.
- Filter the crystals using a filter funnel and filter paper.
Ammonia can be used to make the fertilisers ammonium nitrate, and
ammonium sulphate.
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H Why is salt so important?
Sodium chloride is common salt.
We get sodium chloride from:
- The sea.
- Salt deposits in rocks.
Sodium chloride is used as:
- A preservative
- A flavouring
Salt (sodium chloride) is mined:
- By using rock cutters deep underground. This can cause
subsidence (the land caves in where the rock has been cut
away.)
By drilling a big hole (bore hole), pumping down water to dissolve the
salt, pumping the salty water back up to the surface.
We can get useful chemicals from sodium chloride by electrolysis
(using electricity to split it up):
- Chlorine for bleach, plastics and to sterilise water.
- Hydrogen to make margarine.
- Sodium hydroxide to make soap.
Electrolysis of brine (sodium chloride solution = salty water) produces:
- Chlorine gas at the anode.
2Cl- - 2eCl2 Oxidation (Loss of electrons)
- Hydrogen gas at the cathode.
2H+ +2eH2 Reduction (Gain of electrons)
- Sodium Hydroxide is also made.
Inert (unreactive) electrodes must be used to stop other chemicals
being made.
The test for chlorine = it bleaches moist litmus paper and turn
universal indicator red.
The test for hydrogen gas = it make a lit splint ‘pop’
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