Chemistry Unit 1 Flashcards
How is ethanol made and what are the advantages and disadvantages?
Made by fermentation of plants
Carbon dioxide released was taken in by the plant as it grew and the only other product is water
Engines need to be converted to work with ethanol and it isn’t widely available
What is a mixture?
A mixture consists of multiple elements or compounds that aren’t chemically bonded to each other
How is biodiesel made and what are its advantages and disadvantages?
Produced from vegetable oils
Carbon neutral, engines don’t need conversion, produces hardly any sulphur dioxide or particulates
Can’t be made fast enough to replace diesel and it is expensive to make
What is the problem with releasing carbon dioxide into the atmosphere?
Causes global warming which causes other types of climate change and risk of flooding due to the polar ice caps melting
What are the 3 alternative fuels to hydrocarbons?
Ethanol
Biodiesel
Hydrogen gas
What are the 2 other ways of reducing sulphur emissions?
Reduce usage of fossil fuels
Power stations have acid gas scrubbers to take harmful gases out before fumes are released into the atmosphere
What 2 products do we usually get from cracking?
Fuels like petrol and paraffin
Simple hydrocarbons like ethene which is needed for making plastics
What happens when there isn’t enough oxygen and what is this called?
When partial combustion happens, solid particles (particulates) of soot (carbon), unburnt fuel and carbon monoxide are released
What does cracking turn diesel into?
Petrol, paraffin and ethene
Describe how acid rain is caused
Sulphur dioxide is released into the air as a by-product of burning hydrocarbons
Sulphur dioxide mixes with clouds to form sulphuric acid which falks to the ground as acid rain
How does burning hydrocarbons cause acid rain?
The sulphur impurities in the oil is released as sulphur dioxide when the fuel is burned
Why is petrol suitable for car fuel?
A liquid can be stored in the engine easily
It is easily vaporised so it can mix with the air before ignition
What does saturated mean?
When all atoms have made bonds with as many other atoms as they can
Only single bonds
What are very viscous hydrocarbons used for?
Lubricating engine parts and covering roads
Why is refinery gas suitable for use as bottled gas?
Its volatility allows it to be used as a gas at room temperature
How do branching chains or lined-up chains affect a plastic?
Branching chains are softer, easier to melt and lower density
What are the 3 basic trends of hydrocarbons?
The shorter the molecules, the less viscous (less gloopy) it is
The shorter the molecules, the more volatile it is (turn into gas at lower temperature)
The shorter the molecules, the more flammable it is
What are the 3 disadvantages of crude oil?
It is limited and unsustainable
Burning them creates pollution
The ways that we obtain crude oil can scar the landscape
What type of reaction does cracking use?
Thermal decomposition
What is complete combustion?
When there is enough oxygen and all of the fuel is burned
Describe the procedure of cracking
The long-chain hydrocarbon is heated until it is vapourised
The vapour is passed over the powdered catalyst which is aluminium oxide at a temperature of 400 to 700 degrees C
The long-chain molecules split apart on the surface of the specks of aluminium oxide
What are the 2 environmental problems with crude oil?
Oil spills can cause damage to animals
Burning it to release energy causes global warming, global dimming and acid rain
What is the chemical equation for burning a hydrocarbon?
Hydrocarbon + oxygen
–> carbon dioxide + water vapour
What is the place where fractional distillation happens called?
The fractionating column
What is cracking?
Splitting up long-chain hydrocarbons into more desirable short-chain hydrocarbons
How is hydrogen gas made and what are its advantages and disadvantages?
Electrolysis of water
Combines with oxygen in the air to form water
Expensive engine, need energy from another source to make it, hard to store because it’s explosive
What is the formula that tells us how many hydrogens or carbons there are in an alkane?
The number of carbons is n
The number of hydrogens is 2n+2
What decides where a hydrocarbon will condense?
The length of the molecule
The longer the molecule, the higher the temperature when it condenses
What are alkanes?
Chains of carbon atoms surrounded by hydrogen atoms
Give 4 advantages of crude oil
Burned to make energy and heat for homes
Make chemicals and plastics
Easiest and cheapest to use because things are made to use these fuels
Very reliable
What is global dimming?
The fact that less sunlight has been reaching the surface of the Earth over time
List all of the types of hydrocarbons outputted from the column from bottom to top
Bitumen (road material)
Oil
Diesel
Kerosene (jet fuel)
Naphtha
Petrol
Refinery gas (bottled gas)
What are the first 4 alkanes?
Methane (natural gas)
Ethane
Propane
Butane
What is crude oil?
A mixture of different hydrocarbons
What causes global dimming?
Particles of soot and ash that are produced when fossil fuels are burned reflect sunlight back into space
How do we separate all of the different hydrocarbons in crude oil?
Fractional distillation
Describe how fractional distillation works
Crude oil is put into the bottom of the column and the bottom is heated
The vapourised oil travels up the column and condenses in fractions of different heights depending on the type of hydrocarbon (the temperature decreases as you go up the column)
Every fraction has an outlet where its type of hydrocarbon can be let out
At the top of the column, the refinery gas is collected (this still hasn’t condensed)
What are hydrocarbons?
Fuels made from carbon and hydrogen
When are nitrogen oxides released when burning hydrocarbons?
When the combustion is taking place at high temperature
What are the 2 problems with removing the sulphur from fuels before burning them?
More expensive
Uses energy causing the release of more carbon dioxide
What are the 2 useful properties of emulsions?
Thicker than oil or water
The more oil in an emulsion, the thicker it is
What is the disadvantage of emulsifiers?
Some people are strongly allergic to emulsifiers
What is an emulsion?
A mix of oil and water where one is suspended inside the other
What are the 2 advantages of emulsifiers?
Stop emulsions from separating out giving them a longer shelf-life
Allows production of food that is low in fat and still has a good texture
What are the 3 main everyday emulsions?
Mayonnaise
Milk
Whipped cream (contains air too)
What are the 2 types of emulsion?
Oil-in-water emulsion
Water-in-oil emulsion
Describe an emulsifier molecule
One end is hydrophilic and joins to water and not oil
The other end is hydrophobic and joins to oil and not water
What do we do when oil and water won’t mix?
Mix them with an emulsifier that holds them together
What is the problem with mixing oil and water?
Oil doesn’t dissolve in water
Describe phase 2 of the atmosphere’s evolution
Green plants and algae evolved over most of the Earth because they could use the carbon dioxide
The green plants and algae absorbed the carbon dioxide and produced oxygen by photosynthesis
The plants and algae died and very buried under layers of sediment and the carbon and hydrocarbons inside them became locked up in sedimentary rocks as insoluble carbonates and fossil fuels
How do we predict when volcanoes will erupt?
The molten rock rises up into chambers near the surface before an eruption
Describe how we get separate the substances of air
Air is filtered to remove dust
It’s cooled to -200 degrees
During cooling, the water vapour condenses and carbon dioxide freezes and they are both removed
The liquid air enters a fractionating column and is heated slowly
Oxygen and argon come out of the bottom together so another column is used to separate them
Nitrogen gas comes out of the top
Why does the mantle slowly flow?
Within the mantle, radioactive decay takes place which produced a lot of heat causing the mantle to flow in convection currents
What are tectonic plates?
The crust and upper mantle are split into a number of large pieces called tectonic plates
Why do earthquakes happen?
When two plates have built up pressure when trying to move past each other and they suddenly move, a shockwave happens that causes an earthquake
Why do the plates drift and how fast do they do this?
The convection currents in the mantle cause the plates to drift a few centimetres a year
Why is carbon dioxide bad for the oceans?
The extra carbon dioxide we are making is making the oceans too acidic so that some species won’t be able to survive
Describe the theory of primordial soup
The Earth’s atmosphere contained hydrocarbons, ammonia and other gases billions of years ago
Lightning struck causing a chemical reaction between the gases forming amino acids
The amino acids collected in a body of water out of which life eventually crawled
What 3 things did Wegener find that made him make his theory?
Identical fossils were found on the opposite sides of the Atlantic Ocean
Africa and South America seemed to fit together like a jigsaw
There were matching layers in the rocks of different continents
What is Wegener’s theory of continental drift?
That all continents were once part of a supercontinent called Pangaea and that the continents split up and drifted apart
What did Miller and Urey do to try to prove the theory?
They sealed the gases in their apparatus, heated them and applied an electrical charge for a week
Amino acids were made but not as many as there are on Earth suggesting that the theory is on the right lines
Describe phase 1 of the evolution of the atmosphere
The Earth’s surface was originally molten so that any atmosphere just boiled away into space
The surface cooled down a bit and a thin crust formed
Volcanoes gave out lots of gas like carbon dioxide and small amounts of methane, ammonia and water vapour
Ocean formed when the water vapour condensed
Who were the scientists that tried to prove the “primordial soup” theory?
Miller and Urey
What is the big problem with earthquakes specifically?
We can’t predict when they will happen
Give 3 reasons why Wegener’s theory wasn’t accepted for a long time?
He thought that it was caused by tidal forces and the Earth’s rotation which scientists calculated to be impossible
He had used inaccurate data in his calculations meaning his predictions about how fast the continents were moving apart were very wrong
He had studied astronomy so he wasn’t considered a reliable geologist
Describe the Earth’s structure
The outside is called the crust and is 5 to 50 km thick
The mantle is below the crust and has all the properties of a solid except that it flows very slowly
At the centre, is the core which is made from iron and nickel
Describe phase 3 of the atmosphere’s evolution
The oxygen killed off some early organisms but allowed more complex organisms to evolve
The oxygen also created the ozone layer (O^3) which blocked harmful rays from the Sun and enabled even more complex organisms to evolve
What are the properties of titanium?
Low density (light)
Very strong
Corrosion resistant
What are the properties of aluminium?
Corrosion-resistant
Low density (light)
Not strong when pure but very strong when alloyed
What are gold alloys used for?
Jewellery
Pure gold is too soft
What are the properties and uses of high carbon steel?
Very hard and inflexible and is used for blades for cutting tools and bridges
Give 3 everyday uses of metals
Their strength and malleable make them good for car bodies and bridges
Useful for things that heat needs to travel through (saucepan bases)
Electrical wires because of their electrical conductivity
What are the properties of copper?
Good conductor of electricity
Hard and strong but can be bent
Doesn’t react with water
What are the 2 main disadvantages of using metals?
Some corrode when exposed to air and water
They can get “metal fatigued” when they are constantly stressed and strained leading to metals breaking
What is an alloy?
A mix of 2 or more metals
What are the properties and uses of low carbon steel?
Easily shaped and is used for car bodies
What is stainless steel made from?
Iron and carbon with added chromium and nickel
Which metals are the transition metals?
The middle block on the periodic table
What are the 4 basic properties of metals?
Strong
Malleable
Conduct heat
Conduct electricity
What is the problem with pure iron?
It is extremely malleable
What are the properties and uses of stainless steel?
Corrosion-resistant and is used for cutlery and containers for corrosive substances
What are aluminium alloys used for?
To make aircrafts
Aluminium alloys are much stronger than pure aluminium
Why are alloys harder than pure metals?
The different sized atoms will upset the layers of pure metals making it more difficult for them to slide over each other
Why is pure iron so malleable?
The arrangement of atoms is very regular so the layers can slide over one another very easily
What is cupronickel made from and used for?
Copper + nickel
Hard and corrosion resistant
Used to make “silver” coins
What is steel?
An alloy made from iron and carbon
What is bronze made of and used for?
Copper + tin
Harder than copper
Good for medals and statues
What is iron like when it comes straight from the blast furnace?
Usually 96% iron and 4% carbon
It is very brittle so it doesn’t have many uses
Called cast iron
What are the 5 advantages of limestone?
Provides roads, houses and some chemicals
Used to neutralise acidic soil and acidity in lakes and rivers
Used in industrial chimneys to neutralise sulfur dioxide to prevent acid rain
The quarry industry provides jobs for people
Once quarrying is complete, landscaping and restoration of the area is legally required
What is limestone made of?
Mainly calcium carbonate (CaCO^3)
What is the problem with building houses out of limestone?
Limestone reacts with sulfuric acid to form calcium sulfate, carbon dioxide and water meaning that acid rain destroys limestone
What is the pH of calcium hydroxide?
It has an alkaline pH because it is a hydroxide
What are the 5 disadvantage of quarrying limestone?
Makes ugly holes in the landscape
The process makes lots of dust and noise
Destroys habitats
Transported by lorries causing more noise and pollution
Waste materials produce ugly tips
Which carbonates also thermally decompose and react with acid in the sane ways as calcium carbonate?
Magnesium, copper, zinc and sodium carbonates
What happems when calcium carbonate reacts with an acid?
A calcium salt, carbon dioxide and water are formed
What are the 2 reasons that making things out of limestone causes pollution?
Cement factories make a lot of dust causing breathing problems
Energy is needed to make cement which comes from burning fossil fuels
What are the 2 uses of calcium hydroxide?
Neutralise acidic soil in fields
Test for carbon dioxide
How is calcium hydroxide used to test for carbon dioxide?
If gas is bubbled through limewater, the solution will turn cloudy if carbon dioxide is present
The cloudiness is because calcium carbonate is being formed
What is the limestone cycle?
The way that calcium carbonate becomes calcium oxide which becomes calcium hydroxide which becomes calcium carbonate again
How do we make concrete stronger?
Reinforce it with steel bars
How do we get limestone?
It is quarried out of the ground
What happens when calcium oxide reacts with water?
Calcium hydroxide is formed
What decides the type of calcium salt produced?
The type of acid
E.g. Sulfuric acid makes calcium sulfate
What is limewater?
Calcium hydroxide solution
What happens when calcium carbonate is heated?
It thermally decomposes into calcium oxide and carbon dioxide
Why is calcium hydroxide used instead of powdered limestone to neutralise acidic soil?
It neutralises the acidity much faster
Give 6 advantages of limestone products
Perfect for building materials
Widely available and cheaper than marble and granite
More hard-wearing than marble but still attractive
Concrete can be poured into moulds to make blocks which is quick and easy
Limestone, concrete and cement don’t rot like wood when it gets wet
Concrete doesn’t corrode
What is the chemical reaction for calcium hydroxide reacting with carbon dioxide?
Calcium hydroxide + carbon dioxide –> calcium carbonate + water
What is the main use of limestone?
It is usually used for making building blocks and bricks
What are the 3 other uses of limestone?
Powdered limestone and powered clay are heated in a kiln to form cement
Cement is mixed with sand and water to make mortar to hold bricks together
Cement is mixed with sand and aggregate (gravel and water) to make concrete
Describe the process of obtaining plant oil
The plant is crushed and then pressed by 2 metal plates to squash the oil out
The oil is then separated from the plant material with a centrifuge or solvents are used to get the oil out
Distillation refines oil and removes water, solvents and impurities
What is the difference between a monounsaturated fat and a polyunsaturated fat?
Monosaturates have one double bond where polyunsaturates have multiple
What are the 3 reasons that vegetable oils are used in food?
Provide a lot of energy
Variety of good nutrients
Essential fatty acids which the body needs for many metabolic processes
Describe the process of hydrogenation
Unsaturated vegetable oils react with hydrogen in the presence of a nickel catalyst at 60 degrees
The hydrogen has opened up the double bonds
What is the other use of vegetable oils and why are they used for this purpose?
Processed into fuels because they provide a lot of energy
How do we stop unsaturated vegetable oils from being liquids at room temperature?
They are hydrogenated
What is the problem with saturated fats?
They can increase cholesterol in the blood and increase the risk of heart disease
Where does plant oil come from?
Fruits and seeds of plants
What is interesting about the way margarine is hydrogenated and why is this done?
It is only partially hydrogenated so that it is soft enough to spread easily like butter
What is the most common example of a vegetable oil fuel?
Biodiesel
Give one advantage and one disadvantage of hydrogenated vegetable oils
They are much cheaper and they keep longer than butter
Partially hydrogenating vegetable oils means you end up with trans fats which increase cholesterol in the bloof
What are the properties of a hydrogenated oil?
Higher melting points meaning they are more solid at room temperature making them useful for spreads
Are vegetable oils and animal fats usually saturated or unsaturated?
Vegetable oils are usually unsaturated and animal fats are usually saturated
How can you work out if an oil is saturated or not?
If it is added to bromine water and the bromine water turns from orange to colourless, it is unsaturated
What is the problem with cooking in oil or fats generally?
Makes the food more fattening
What are the 3 benefits of using vegetable oil in cooking?
Higher boiling points than water so food can be cooked at higher temperatures
Provides different flavour and brings out the flavour in the food it is cooked with
Increases the energy we get from eating the food
What are the 2 reasons iron is used to extract copper?
It is more more reactive than copper
It is cheaper than copper
How is the carbon monoxide for this reaction obtained?
Coke (containing carbon) burns on air to produce heat and reacts to form carbon monoxide
How are metals more reactive than carbon extracted?
Using electrolysis of molten compounds
What is electrolysis?
The breaking down of a substances using electricity
What do we do to cause reduction with carbon?
Heat the metal oxide (and carbon) in a blast furnace
What are the anode and cathode?
Anode is positive electrode
Cathode is negative
What are the 2 main ways of extracting metals from ores?
Reduction
Electrolysis
Describe phytomining of copper
Plants are grown in copper-rich soil and the copper builds up in the leaves
The plants are burned in a furnace and the ash has copper in and is collected
Which metals don’t have to be extracted from rocks and why?
Unreactive metals don’t usually form compounds so they can be found as the metal itself
What does an electrolyte have to have?
Free ions
Describe how limestone is used in the blast furnace
The calcium carbonate reacts with the acidic impurities in the iron by reacting with them to form molten slag
Describe bioleaching of copper
Bacteria separate copper from copper sulfide by getting the energy from the bond between the copper and sulfur
The leachate (solution produced) is filtered to extract the copper
Why do we need to recycle as much copper as possible?
Copper-rich ores are short in supply
How can we work out if a metal can be extracted using reduction with carbon and why?
If the metal is below carbon in the reactivity series it can be reduced with carbon
This is because the carbon is more reactive so it will bond with the oxygen faster than the metal
What are the anode and cathode made from?
They are both carbon (graphite)
What is the electrolyte?
The liquid (can be molten or solution) that is to be broken down and conducts electricity
How do we lower the melting point of the aluminium oxide in electrolysis?
Cryolite is added
What is reduction with carbon?
When carbon reacts with the metal oxide to form the metal and carbon dioxide
How does electrolysis work?
The positive ions go towards the negative electrode where they lose electrons and become the pure atoms
The negative ions gain electrons at the positive electrode and become the pure atoms
What is an ore?
A rock which contains enough metal to make it worthwhile extracting it
What is the advantage and disadvantage of bioleaching and phytomining?
New methods of extraction don’t destroy the environment but they are very slow
Why is electrolysis used on copper?
Copper has to be purified so that it can be used in wires
What are the 2 disadvantages of metal extraction?
Bad for the environment (mines, noise, loss of habitats)
Deep mine shafts are dangerous
Describe the displacement reaction used to extract copper
Copper sulfate + iron –> iron sulfate + copper
This is because iron is more reactibe than copper
What are the 4 reasons for recycling metals?
Lots of energy used, fossil fuels burned
Lots of energy used, recycling saves money
Finite amount of metals in Earth, recycling saves them
Cuts down metals sent to landfill
What is the chemical equation for extracting metals using thermal decomposition?
Metal oxide –> mercury + oxygen (gas)
Which metals are found as the element (native)?
Gold and platinum
How are metals purified?
Using electrolysis
Which type of compounds are usually found as ores?
Oxides
E.g. Aluminium oxide
What is the other way of extracting metals?
Thermal decomposition
What are the 2 new methods of extracting copper?
Phytomining
Bioleaching
What are the 2 advantages of metal extraction
Useful products made
Provides money and jobs to local people
What is the other way that iron can be extracted in a blast furnace?
Iron oxide + carbon monoxide –> iron + carbon dioxide
Which metals can be extracted using thermal decomposition?
Mercury and silver
What is the other way that copper can be extracted?
A displacement reaction with iron
Why do we try to use reduction with carbon instead of electrolysis?
Electrolysis is much more expensive because the metal oxides have to be molten and the electricity is expensive
Why is electrolysis to extract aluminium so expensive?
The aluminium oxide has to be melted at a very high temperature
Why do anodes have to be replaced?
The oxygen reacts with the carbon anode to form carbon dioxide
What is a displacement reaction?
AB + C (more reactive than A) –> CB + A
