AQA Chemistry Unit 1

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C1.1- Atoms and Elements

An element is made up of just one type of atom 

All known elements are listed in the periodic table. The vertical columns are called groups, and the horizontal rows are called periods. The elements in a group all have similar properties. 

For example, the elements in group 1 are all silve coloured metals which react with water

The elements in group 0 are gases at room temperature, and do not normally react with other substances

The elements on the left hand side of the table are metals. The elements on the right are non-metals. Those in the middle of the table are known as transition metals.

Each element has its own symbol, made up of 1-2 letters. These are used worldwide by all chemists to represent the element clearly.

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C1.2- Inside Atoms

At the centre of an atom is its nucleus. This contains both protons and neutrons. Around the outside of the atom are the electrons. 

Name of particle          Mass             Charge                  Location

Proton                              1                     +1                        Nucleus

Neutron                            1                      0                         Nucleus

Electron                     Almost 0                -1                        Outside the nucleus

An atom has an equal amount of protons and electrons, giving it an overall charge of 0.

 The number of protons in an atom is its atomic number. The sum of protons and neutrons in an atom is its mass number. 

Electrons are arranged in energy levels. The first energy level always has a maximum of two electrons, with every one after that having a maximum of eight. All elements in the same group have the same amount of electrons in the outer shell, giving them similar properties. 

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C1.3- Inside Compounds

Compounds are made up of two or more elements, joined by a bond. The properties of a compound are different to the properties of the elements that make it up. 

Ionic Bonds

All atoms aim to have a full outer shell by either losing or gaining electrons from other atoms. Losing or gaining an electron causes the atom to become charged, meaning it is no longer an atom- it is an ion. When two atoms have gained or lost electrons to or from the other, they both now have opposite charges. This causes them to be attracted to each other. 

Ionic bonds are made up only of metals and non-metals. 

Covalent Bonds

Covalent bonds are made up of two non-metals. There are no electrons to give away from the atoms, so atoms instead share pairs of electrons when they bond. 

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C1.4- Chemical Reactions

In all chemical reactions, the atoms of the starting materials are called the reactants. These are rearranged into new substances, called products. Most chemical reactions are irreversible, meaning the products cannot be reverted back into the reactants. 

Word equations show only the reactants and products of a chemical reaction. To explain how the atoms are rearranged in the reaction, you need a symbol equation. 

Before writing a symbol equation, it is necessary to know the symbols and formulae of the reactants and products. Each atom has its own symbol; each compound has its own formula. The small numbers next to letters in a formula show how many of that particular atom are in the compound. When balancing an equation, you can only add large numbers to the front of a formula, which multiplies all of the atoms in the formula by that number. 

When you have a balanced symbol equation, you can see the way in which the atoms of the products are rearranged and what other atoms they bond with in order to form the products. 

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C1.5- Chemical Equations

The word equation for the burning reaction of titanium is 

titanium + oxygen → titanium dioxide 

As atoms cannot be created or lost in a chemical reaction, if 48g titanium reacts with 32g oxygen, the product (titanium dioxide) will be 80g. 

A balanced symbol equation shows how the atoms are rearrabed and the relative amount of the substances that take part in a reaction. This is the balanced symbol equation of the burning reaction of titanium (with subscript 2 in O2):

Ti + O2 → TiO2  

It is balanced because there are the same amount of titanium atoms (one) on each side, and the same amount of oxygen atoms (two) on each side of the arrow. 

When balancing equations yourself, you cannot add subscript (small) numbers because this changes the formula. You must add large numbers to the beginning of a formula, which multiples everything to the right of it by the number. 

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C1.6- Limestone

Limestone (comprised mainly of calcium carbonate) was formed from the shells of creatures that lived in shallow waters millions of years ago. It is often crushed up and used as aggregate, or a raw material for building materials such as cement, mortar and glass. Calcium carbonate reacts with acid to form a salt, water and carbon dioxide. For this reason, limestone buildings and statues react severly with acid rain, often in the form of corrosion. 

Benefits of quarrying limestone

  • Many quarries are in the countryside, which provides jobs for those in the rural areas
  • Local families and facilities are economically benefitted by limestone quarrying
  • The UK exports a lot of limestone, economically benefitting the economy

Problems of quarrying limestone

  • Some quarries are in attractive areas of the countryside, ruining the scenery and damaging the local tourist industry
  • Transporting the limestone causes a lot of congestion
  • The quarries also take up land space, making it unavaliable for farming and recreation
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C1.7- The Lime Cycle

The Lime Cycle begins with calcium carbonate.

It is heated, and some carbon dioxide is lost. The remaining product is calcium oxide (or quicklime).

Water can be added to calcium oxide, causing solid calcium hydroxide (slaked lime) to form.

If the solid calcium hydroxide has more water added to it and is then filtered, it forms a calcium hydroxide solution, also known as limewater.

Limewater is also the test used for carbon dioxide, and when carbon dioxide is added to it, it reverts back to calcium carbonate. The cycle repeats. 

Calcium oxide and hydroxide both form alkaline solutions in water. They can both be used to neutralise excess acidity in lakes and soils or waste gases produced from burning coal in power stations. 

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C1.8- Products from Limestone

Cement

  • Crush limestone into pieces
  • Add powdered clay
  • Heat mixture in a rotating kiln
  • Add calcium sulfate powder

Mortar (sticks bricks together)

  • Mix cement, sand and water together

Concrete 

  • Mix cement, sand, aggregate and water

Calcium carbonates decomposes (when a single compound breaks down into 2+ atoms/compounds) when limestone is heated to make cement. Carbonates of metals low in the reactivity series need little energy to break them down. The higher up it is in the reactivity series, the more energy needed. Some do not decompose at temperatures as low as bunsen burners. 

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C1.9- Magnificent Metals

The metals in the block in the middle of the periodic table are known as transition metals. They:

  • have a shiny surface when freshly cut
  • are malleable (bent/hammered into shape without cracking)
  • are good conductors of heat and electricity

Gold- one of the first metals to be discovered. It is so low in the reactivity series that it is found 'native' (not bonded to anything else) in nature. It very rarely joins other elements to form compounds and is now rare because it used to be so easy to find. 

Iron- too reactive to be found on its own in the crust. It joins to other elements forming natural compounds called minerals, which are often mixed with sand or rock. Rocks containing useful minerals are called ores. Iron is extracted from an ore by heating it in a hot blast furnace with coke (carbon) and the oxygen is removed in reduction reactions. 

Other metals- metals below carbon in the reactivity series are also extracted by heating their oxides with carbon because carbon reduces metal oxides. 

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C1.10- Stunning Steel

Iron straight from the blast furnace isn't pure iron. It has about 3% carbon in it, as well as other impurities, which make it very brittle. 

Cast Iron is formed by re-melting blast furnace iron and adding scrap steel. It is much stronger than blast furnace iron and is used for cannons and cooking pots. Pure Iron is formed by removing impurities from blast furnace iron. It has a regular arrangement of atoms. The layers of these atoms slide over each other easily, meaning it is malleable and soft. Steel is created by mixing mainly iron with some carbon and other metals to change its properties. Steels are a good example of alloys. Alloys are mixtures of metals with other elements. 

The properties of an alloy depend on its atom arrangement. In steel, the carbon and metal atoms get between the iron atoms, distorting the regular pattern and preventing the iron atoms sliding over each other. This makes it stronger than iron. 

Carbon steels with less than 0.3% carbon are easy to make into shapes and are used for food cans and car body panels. High carbon steels (between 0.6 and 1%) are much harder and stronger. Stainless steels do not rust or corrode because of the chronium atoms in it. 

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C1.11- Copper

Properties of Copper

  • Malleable (good for plumbing)
  • Conducts electricity (good for making wiring)
  • Conducts heat (good for making pans)
  • Mixes with nickel to make a hard alloy (for coins)

Most copper in the earth's crust is joined to other elements. Companies dig the ore up from open cast mines, then concentrate the ore to separate the copper from the waste rock. Pure copper is obtained by one of the following methods:

1.  Heat the ore in a furnace (smelting) then purifying the copper through electrolysis

2.  Making a solution of copper compounds from the ore and using electrolysis

3.  Planting certain plants over low-grade copper ores (phytomining)

4.  Using electrolysis to extract metal from copper compound solutions from bacteria (bioleaching)

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C1.12- Titanium and Aluminium

Properties

Alumnium on its own is very soft, but when an aluminium alloy is formed with iron and silicon, it becomes much harder. Aluminium has a very low density, so is very light, and also has a thin layer of alumnium oxide on its surface, which prevents corrosion. It is used in aeroplanes, overhead power cables, cooking foil and drink cans. 

Titanium also has a low density and resists corrosion. Titanium catces fire more easily than most metals, but it is still often used for aeroplanes, oil rigs, artificial hips and bone pins. 

Extraction

The aluminium we use came from from aluminium oxide in bauxite ore, and titanium exists naturally as titanium oxide. Neither aluminium nor titanium can be extracting by heating their ores with carbon. Aluminium is above carbon in the reactivity series, so its atoms are joined very strongly to oxygen in bauxite. Titanium oxide heated with carbon makes titanium carbide, which is very brittle. Aluminium is extracted by electrolysis. Titanium is extracted in a multi-step process. 

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C1.13- Making Crude Oil Useful

Crude oil is a fossil fuel. It was formed from the remains of animals from millions of years ago. It is non-renewable and finite. 

Crude oil is a mixture, meaning the hydrocarbons compounds that make it up are not chemically joined together. You can separate mixtures by physical means: 

  • filtration (separating a solid from a liquid) 
  • distillation (separating liquids with different boiling points).

Fractional Distillation

Oil companies separate crude oil using fractional distillation, because it isn't much use on its own. This involves heating the oil to 450 degrees. The oil enters the bottom of the column as gas, and the column has a temperature gradient- it is hotter at the bottom and cooler at the top. This causes the different fractions to condense and exit the column as liquids at various points as they all have different boiling points. 

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C1.14- Looking into Oil

Propane and butane are examples of alkanes (saturated hydrocarbons). The carbon atoms in them are joined together by a single bond. Most hydrocarbons in crude oil are also alkanes. In displayed formula, each line represented a single bond between atoms, eg propane and butane:

                   (http://www.bbc.co.uk/staticarchive/d050b8277715ed5cc3587a98a7a35c6e86717704.gif)                     (http://www.bbc.co.uk/staticarchive/71083413523051d66d39fd1fbcf8d1ec381abc23.gif)

A propane molecule consists of 3 carbon atoms joined to 8 hydrogen atoms; butane has 4 carbon and 10 hydrogen. The general formula of an alkane is CnH2n+2 (w/ subscript)

Melting/boiling points- the smaller the molecule, the lower the boiling point. 

Ignition- the smaller the molecules, the more easily it catches fire. 

Viscosity- the longer the chain, the more viscous it is 

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C1.15- Burning Dilemmas

Complete combustion- when fuels react with oxygen to produce energy in a plentiful supply of air

Incomplete combustion- fuels react with oxygen to produce energy when there is limited air

Because coal contains sulfur impurities, it produces sulfur dioxide when it is burned. The sulfur dioxide dissolves in clouds, making acid rain. This has environmental imapcts:

  • makes lakes more acidic, killing some plant and animal life
  • damages trees (washes away nutrients in soil, damages waxy leaf protection)
  • damages limestone buildings (reacts with calcium carbonate)

Limestone powder can be added to waste gases from coal power stations to make calcium sulfate.

 Burning diesel produces tiny pieces of solid material called particulates. They can contribute to global dimming. 

Incomplete combustion (not enougb air reaching the flame) can lead to deadly carbon monoxide being produced in home gas boilers. 

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C1.16- Global Warming

Burning fossil fuels produces carbon dioxide, which causes global warming 

  • 1. Radiation from the sun enters the earth's atmosphere and reaches the earth's surface
  • 2. The radiation warms up the earth's surface
  • 3. Some heat radiated by the surface goes into space; some is absorbed by carbon dioxide in the atmosphere
  • 4. The atmosphere radiates some heat energy back towards the earth. It gets hotter

Global warming has severe impacts on the earth:

  • Climate change- extreme weather, droughts, flooding, risk of extinction, malaria spreading 
  • Melting ice caps- sea levels rise, increasing the risk of flooding to coastal areas

There are solutions to global warming:

  • Using less- governments and councils are urging people to use less fossile fuels where possible
  • Alternative fuels- hydrogen and ethanol can be used to fuel cars, but both have drawbacks
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C1.17- Biofuels

Plant oils make good fuels for cars, buses and trains due to the large amounts of energy they transfer when burned. Two other types of biofuel can be used in vehicles: ethanol (produced from sugar canes) and biodiesel (producing by chemically reacting plant oil/animal fat with an alcohol)

Benefits to using biofuel power stations 

  • Provides jobs for local people
  • Generates energy from renewable sources

Drawbacks to using biofuel power stations

  • Damages biodiversity in rainforests
  • Burning plant oils releases oxides of nitrogen gases, which worsen lung diseases
  • Evicts people from their land
  • Burning rainforests to make way for the oil palms produces more carbon dioxide than saves
  • May be immoral to use food space for growing fuels
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C1 Part 1 Catch Up

  • Each element in the periodic table is made up of one type of atom
  • Atoms have a nucleus (protons and neutrons) and energy shells containing electrons
  • Elements in the same group have the same number of electrons in outer shell and similar properties
  • Balanced equations describe chemical reactions
  • Limestone is a sedimentary rock and is quarried to be used as a building material
  • Limestone is heated with clay to form cement, and cement, water and sand form concrete
  • Metal carbonates are decomposed to form metal oxide and carbon dioxide
  • The elements in the middle block are transition metals 
  • Pure iron is converted into an alloy (steel) by mixing with other elements
  • Metals are extracted from ores by electrolysis, heating or reduction (reacting with carbon)
  • Aluminium and titanium have low densities and do not corrode, but are expensive to extract
  • Crude oil is a non-renewable resource and a mixture of hydrocarbons
  • Burning hydrocarbons releases carbon dioxide (global warming), carbon monoxide (toxic), sulfur and nitrogen oxides (acid rain) and particulates (global dimming)
  • Biofuels (biodiesel, ethanol) are produced from plant material, which releases less carbon dioxide and is a renewable resource
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C1.18- Cracking Crude Oil

The fractional distillation of crude oil makes useful products (for example, petrol polythene bottles and propane in nail varnish remover). However, the supply of the chemicals obtained from crude oil does not always meet the demand. Companies often use cracking in order to break down the large hydrocarbons from crude oil into smaller, more useful molecules. 

Cracking involves heating the oil fraction to a very high temperature, causing the hydrocarbons to vaporise. The vapour then passes over a hot catalyst, and the alkane molecules in the capour break down in thermal decomposition reactions.  

Double bonds

The double line between two atoms in a displayed formula represents a double bond. Double bonds are stronger than single bonds, and they make the compound more reactive. An alkene (unsaturated) contains at least one double bond  An alkane (saturated) contains no double bonds. 

Bromine water can test for double bonds. Orange bromine water becomes colourless when it reacts with unsaturated compounds. The general formula for an alkene is CnH2n (w/ subscript)

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C1.19- Polymers

Polymers are materials with very big molecules. They are made by joining thousands of small molecules, called monomers, together. Polymers are used to make plastic because they have good proterties; they can be strong, flexible and durable. Others are very rigid and can withstand high temperatures. 

The structure of polymers explain their properties. For example, poly(ethene) is:

  • Strong, because atoms in a molecule are joined very tightly together
  • Flexible, because molecules can slide over each other

Polymers can only be made from unsaturated molecules, because the double bonds open up and join the monomers together. This is called a polymerisation reaction. 

For example, the polymer 'polythene' is made by joining together thousands of ethene molecules, because they all have double bonds. 

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C1.20- Designer Polymers

Each polymer has unique properties, depending on what the polymer was made from and the conditions under which it was made. These lead to polymers having different uses as well. 

Poly(ethene)

Poly(ethene) is an example of polymer properties varying. There are two types of poly(ethene): low density poly(ethene), LDPE, and high density poly(ethene), HDPE. 

LDPE is less dense and less strong than HDPE. It has a lower maximum temperature it can be used at, and it is the more flexible of the two. 

  • LDPE molecules have side branches. The branches prevent polymer molecules from lining up in a regular pattern, giving it its lower density
  • HDPE molecules have fewer side branches. The molecules line up in a regular arrangement, so the density is higher. The molecules are also held together more tightly, giving HDPE its strength and high melting point

Dental polymers (used for fillings) have polymers molecules which join together to solidify the paste when UV light is shone on them 

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C1.21- More Designer Polymers

Hydrogels Polymer chains are coild up together. Some polymers can have certain particles removed from them (eg poly(sodium propenoate) can have the sodium removed), leaving uncoild chains. Water molecules are attracted to these uncoiled chains, so the hydrogel can absorb up to 500 times its own weight. Hydrogels are good wound dressings because they give a warm, sterile place to heal, control bleeding well and don't stick to the skin 

Shape memory polymers Shape mempory polymers are smart materials, meaning they change in response to their environment. The shrink wrap that covers DVD cases is a shape memory polymer usually made from poly(ethene). The poly(ethene) is heated until it becomes a liquid and the molecules coil randomly. It is cooled quickly whilst being stretched into a thin solid. The molecules are stretched out and when the film is heated, the molecules return to their coiled shape

Waterproof clothing Most waterproof clothing stops water getting in, but also prevents perspiration from leaving. However, breathable materials have three layers, with the middle one made of a polymer called PTFE. It has tiny holes which are too small for rain to enter through, but big enough for water vapour (the sweat) to exit

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C1.22- Polymer Problems

Many polymers do not react with acids, alkalis or many other chemicals. They are very strong, which makes them useful to us, but they are difficult to dispose of. They can't be decomposed by bacterial action, meaning they are non-biodegradeable. 

Waste plastic can be burnt to release heat energy, but it has to be at very high temperatures to prevent the release of toxic gases. If this heat energy is then not used to generate electricity or heat buildings then it is also a waste of a valuable resource.

Polymers can be recycled, although plastic waste is generally a mixture of different polymers, all of which have to separated by hand in order to be recycled. This is difficult and time consuming.7

Chemists are looking at ways to make polymers biodegradeable. For some polymers, starch can be added during manufacture, and bacteria can break down this starch when it gets wet. Some bags are now made of cornstarch instead of plastic, which is biodegradeable. However, people may object to this, claiming it is unethical to grow maize to make bags when some people do not have enough food to eat. 

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C1.23- Making Ethanol

Ethanol is used as the main ingredient in alcoholic drinks, a solvent in perfumes and after shave, a disenfectant in hand gels and a fuel for cars. There are two ways to make ethanol. The first is fermentation, which has been used for many years. The second is from ethene, which is more recent. 

Ethanol from sugars Wine is made from grapes by fermentation. The glucose in the grapes is broken down by yeast into ethanol and carbon dioxide. The ethanol mixes with the other chemicals in the grapes to make wine. Fermentation works best at 37 degrees. Ethanol for fuel is often made by the fermentation of crops such as sugar canes.

Advantages: renewable source, provides many jobs, requires less energy because it has a lower temperature

Ethanol from ethene Cracking crude oil produces a lot of ethene gas. This can be reacted with steam to make ethanol. A catalyst (usually phosphoric acid) speeds up the process. The process is efficient because there are no waste products. However, it requires crude oil, which is non-renewable. This ethanol is not normally used in drinks, but in solvents and as fuels. 

Advantages: does not use crop land, is a continuous process

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C1.24- Using Plant Oils

Sunflower, rapeseed and soya bean oils are used to cook food because oil has a higher boiling point thatn water, so food cooks quicker. Different oils give different flavours. The three oils mentioned are very good because they can't catch fire until they reach temperatures that are over 200 degrees. Some oils, such as olive oil, are added to food only because of their taste. Plant oils are very useful in types of pastries and biscuits as well, and give them their crumbly texture.

Benefits of oil

  • Very high in energy
  • Provide nutrients (eg vitamin E, which is an antioxidant)
  • Contain oleocanthal (anti-inflammatory)
  • Contain omega-3 fatty acids (reduce heart disease, cancer, bad behaviour)
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C1.25- Oils from Fruit and Seeds

Plants store oil in seeds, fruit and nuts. There are three ways to extract it:

Pressing (with the example of olive oil)

  • Crush olives into paste to release oil from cell vacuoles and mix so oil droplets join
  • Spread paste and compress it to squash liquids out
  • Collect liquid and leave to settle so the oil is on top of the water, then pour off oil and remove impurities

Solvent extraction and distillation (with the example of sunflower seed)

  • Remove hulls from seeds and press seeds to extract oil
  • Add a solvent to the solid remains and use distillation to separate solvent from remaining oil

Steam distillation (with the example of lavender oil)

  • Heat water to vapour and allow it to pass through plant material, so the oil also vaporises
  • The steam and plant oil move to the condenser and become liquid
  • The beaker contains lavender oil and water
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C1.26- Emulsions

Oils and water don't mix without an emulsifier. They will always separate into layers, with the oil on top of the water due to its lower density. They don't mix because the particles are too different; the long vegetable molecules cannot interact with the small water molecules. 

However, when an emulsifier is added to a water and oil mixture, they do not separate and an emulsion forms. Emulsions are more viscous than the liquids they are made of, giving them several uses:

  • Salad dressing (high viscosity allows it to coat leaves well)
  • Ice cream (properties of the emulsion contribute to texture and appearance)
  • Paint (texture and viscosity allows it to coat walls)

Artificial emulsifiers are identified by E-numbers, which have been tested and licensed by the European Union

Emulsifier molecules work because they have a hydrophobic end (attracts oil) and hydrophilic end (attracts water). This brings disperses the molecules out, preventing the formation of layers.

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C1.27- Making Margarine

Butter, margarine and olive oil are all mixtures containing carbon, hydrogen and oxygen, and they all give similar amounts of energy. They also have several differences:

  • Melting/boiling points Butter and margarine are solid at room temperature, whereas oil is liquid. Butter is saturated, meaning has no double bonds. Plant oils are unsaturated, meaning they have a double bond. Monounsaturated fats have one double bond per hydrocarbon chain, and polyunsaturated fats have several double bonds per hydrocarbon chain. 
  • Health effects Saturated fats raise blood cholserterol, so increase the risk of heart disease. Unsaturated fats are much healthier, and may even lower blood cholesterol.

Food companies harden unsaturated vegetable oils by adding hydrogen gas. This hydrogenation reaction adds the hydrogen atoms to the carbon atoms with the double bonds. 

Hydrogenation reactions convert unsaturated fats into saturated ones. The result has a higher melting and boiling point, is solid at room temperature and is spreadable. 

Orange bromine water turns colourless in the presence of unsaturated fats, and vice versa because the bromine atoms join to the double bonds present in unsaturated fats. 

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C1.28- Inside the Earth

The earth is made up of several layers:

  • Crust (thin in comparison to other layers)
  • Mantle (solid properties, goes down halfway to centre of the earth)
  • Core (inner and outer made of iron and nickel)

Features of the crust

Previous belief- the earth was cooling and shrinking after its creation, which caused the crust to wrinkle into continents and volcanoes like on the skin of a drying apple

Wegeners's belief- he suggested the continents were once all joined together and were slowly moving apart (continental drift). His evidence was the shape of the continents and the fossils and rock types found at coastlines

People were reluctant to believe Wegener because they could not comprehend how the continents had once fit together and how they could have moved, and also because Wegener was not a geologist. 

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C1.29- Moving Continents

The theory of tectonic plates states that the earth's crust is made up of around twelve large parts of rock called tectonic plates. They are less dense than the mantle so rest above it. Convection currents in the mantle cause the plates to move at a few centimetres a year. 

Earthquakes

When two plates move alongside each other, they experience friction. The build up of friction causes them to get stuck with huge forces building up between the plates. They suddenly slip, causing an earthquake. Undersea earthquakes can cause huge tsunamis 

Volcanoes

A volcano is a vent in the earth's crust from which magma, ash and gases erupt. The signs of an eruption include nearby earthquakes, a change in the volcano shape and more gas release 

Mountains

Mountains may form when two plates collide. The rocks at the edge of the plates buckle and form mountain ranges

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C1.30- Gases in the Air

Nitrogen and oxygen make up around 99% of the earth's atmosphere. There are also other gases, such as carbon dioxide, water and argon. The atmosphere is a vital source of raw materials for many processes (eg nitrogen makes ammonia for fertiliser, oxygen treats hospital patients, argon is used for filaments lightbulbs). Companies have to separate the gases in the air to use them. 

All the gases have different boiling points. This is what allows companies to separate them:

  • The air is cooled to -200 degrees in stages so that the gases condense to form a mixture of liquids. As it cools:
    • water vapour condenses and is removed
    • carbon dioxide freezes at -79 degrees and is removed
    • oxygen and nitrogen then freeze at their boiling points
  • The mixture of liquid oxygen, liquid nitrogen and liquid argon by fractional distillation
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C1.31- Forming the Atmosphere

Phase One- The Volcanoes

During the first billion years of the earth's life, there was a lot of volcanic activity. This released water vapour, carbon dioxide, ammonia and methane, forming the early atmosphere. 

Phase Two- Plant Life

When plants evolved from early life forms, they began to carry out photosynthesis. Carbon dioxide was also removed from the atmosphere as it was trapped in rocks and fossil fuels. 

The Start of Life

The Primordial Soup Theory suggests that gases in the early atmosphere were reacted together in the presence of sunlight and lightning to form more complex compounds that formed the basis of early life. Two scientists developed the Miller-Urey Experiment, which simulated a lightning spark in amongst a collection of gases that would have been found in the early atmosphere. Compounds had formed from which proteins in living cells are made, giving proof that this was how early life was formed. 

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C1.32- The Carbon Cycle

Carbon dioxide is added to the atmosphere in the following ways:

  • Animal respiration
  • Combustion of fossil fuels
  • Deforestation
  • Decay of microorganisms
  • Evaporation of oceans

It is removed in the following ways:

  • Photosynthesis
  • Dissolved in oceans

As the world's population has increased, the demand for and combustion of fossil fuels has increased. This has led to carbon dioxide being released into the atmosphere faster than it is naturally removed, which causes global warming. The consequences of global warming include changing weather patterns and rising sea levels because of the melting ice caps. 

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C1 Part 2 Catch Up

  • Cracking uses heat and a catalyst to break down long chain alkanes into smaller molecules, including alkenes
  • Alkenes are unsaturated carbons which contain double bonds
  • Alkenes are used to manufacture polymers. In polymerisation reactions, many smaller molecules join to form one large molecule
  • Polymers have a wide range of properties which determine its use
  • The disposal of non-biodegradeable polymers causes environmental problems
  • Ethanol is formed by fermentation or ethene reacted with steam
  • Plant oils have a high energy content, high boiling point and are used in food and cooking
  • They can be hardened in a hydrogenation reaction by adding hydrogen atoms 
  • Plant oils are extracted using pressing, solvent extraction and distilliation or steam distillation
  • They do not dissolve in water, but can be made into an emulsion using emulsifiers
  • The earth has a layered structure. The crust sits on top of a liquid mantle, which is above a hot iron and nickel core
  • The early atmosphere of the earth was mostly carbon dioxide, water, methane and ammonia
  • Rock formation, plant life, dissolving gases and volcanic eruptions changed the atmosphere 
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