Chemistry mock revision

Topic1,1a Sat 6th ATOMS + ELEMENTS

In the nucleus of an atom, there is protons and neutrons.Protons have a positive charge, neutrons have no charge.On the outside of the atom, moving around the shells, are electrons.Electrons have a negative charge, counter-balancing the protons.

Topic 1,1a

Elements are made up of 1 type of atom.E.G. Copper is made up of copper atoms, oxygen of oxygen atoms etc.Elements are shown on the periodic table.They are presented with 2 numbers.The larger number is the atomic mass.Number of protons + number of neutrons = atomic mass.The smaller number is the atomic number /proton number.Number of protons = atomic number.Number of electrons = atomic number.Atomic mass - atomic number = number of neutrons.

Topic 1,1a

Electron shells can only contain a certain number of electrons on each.The sequence is 2, 8, 8. (1st shell, 2nd shell, 3rd shell).This sequence is called the electronic structure.E.G. The atomic number of Phosphorus is 15.        This means Phosphorus has 15 electrons.        Therefore, the electronic structure of Phosphorus is 2, 8, 5.

Topic 1,1a

Atoms join together to make compounds when different elements react.Ionic bonding:A compound formed from a metal and a non-metal.The metal gives the non-metal electrons from its outer shell.This means the metal has formed positive ions.And the non-metal has formed negative ions.The opposite charges attract them to each other.Covalent bondingA compound formed from two non-metalsThe atoms share electrons to fill their outer shells.

Topic2,1a Sun 7th USING LIMESTONE

The limestone cycle:1. Limestone starts as sedimentary rock (Calcium carbonate CaCO3).    When heated, Calcium oxide (+ carbondioxide in atmosphere) is created.2. Now we have quicklime (Calcium oxide CaO).    When hydrated (added water) Calcium hydroxide is created.3. Now we have slakedlime (Calcium hydroxide Ca(OH)2)    When dissolved (excessed water) lime water is created.We can blow gas through lime water to test for CO2. if CO2 is present, lime water will go cloudy.

Topic 2,1a

Limestone is also used to make useful things:Powdered limestone is heated with powdered clay to make cement.Cement can be mixed with sand and water to make mortar.Cement can be mixed with sand and aggregate to make concrete.Limestone can be made into blocks for building.St Paul's cathedral is made from limestone.

Topic 2,1a

Disadvantages of quarrying limestoneEnvironmental problems:Huge holes that permanently damage the environment.Lots of noise and dust in quiet places.Destroys animals habitats.Needs to be transported in lorries - pollution and noise.Waste materials cause tips.Limestone products cause environmental problems such as:Cement factories cause pollution and a lot dust.Energy is needed to produce products - usually burning fossil fuels.

Topic 2,1a

Advantages of quarrying limestoneProvides things that people want such as houses and roads.Chemicals used making dyes, paints and medicines come from limestone.Limestone products are used to neutralise acidic soils.Used in power station chimneys to neutralise sulphurdioxide (acid rain).The quarry brings jobs, helping the local economy.(Leading to local improvements)Landscaping and restoration is usually put into place after quarrying.

Topic 2,1a

Disadvantages of limestone products:Some products are unattractive such as concrete.Concrete cracks easily.Advantages of limestone products:Most products are cheap and easy to cut.Very hard-wearing yet still attractive.Quick to use.Most products don't rot, cant be eaten by insects and are fire-resistant.Doesn't corrode.

Topic2,1b sun 7th CRACKING CRUDE OIL

Cracking means splitting up long chain hydrocarbons.Long chain hydrocarbons e.g. tar aren't very useful.So, they are split up by a process called cracking.Some of the products of cracking are useful as fuels e.g petrol and paraffin.Some are useful as other things such as ethene (for making plastic).DIESEL   CRACKING     Petrol                                Paraffin                                Ethene

Topic 2,1b

Cracking is a thermal decomposition reaction (breaking molecules with heat).First, the long chain hydrocarbon is heated to turn it into a gas.Second, the vapour is passed over a powdered catalyst (400-700 degrees c).The long chain hydro carbon splits/cracks on the surface of the catalyst.(Aluminium oxide is the catalyst used).Most of the products of cracking are alkanes and some are alkenes.

Topic 3,1a mon 8th METALS FROM ROCKS

Some unreactive metals are found in the earth as the metals.Others are extracted from rocks.A metal ore is a rock containing a lot of metal.In many cases, it is an oxide of the metal.E.G. An aluminium ore is called bauxite, it is aluminium oxide. (Al2O3)Most metals can be extracted from their ores using a chemical reaction.The economics of a metal can change over time.E.G. if the market price of a metal drops, it might not be worth extracting it.      if the price increases, it might be worth extracting more of it.      over time, as technology improves, more metals are worth extracting.

Topic 3,1a

Metals are extracted from their ores chemically, by reduction.Or with electricity, by electrolysis.Some ores may have to be concentrated, before the metal is extracted.Electrolysis can also be used to purify the extracted metal.If the metal is above carbon in the reactivity series, it has to be extracted by electrolysis.If the metal is below carbon, it can be extracted by reduction using carbon.This is because carbon can only take the oxygen away from metals that are less reactive than carbon itself.

Topic 3,1a

ReductionMetals lower than carbon in the reactivity series can be extracted using this method.A metal can be extracted from its ore chemically by reduction, using carbon.When an ore is reduced, oxygen is removed.E.G.  2Fe2O3     +    3C        -->  4Fe   +      3CO2     Iron oxide   +  Carbon    --> Iron   +  Carbon dioxide

Topic 3,1a

Electrolysis:Metals higher than carbon in the reactivity series can be extracted using this method.Electrolysis is the breaking down of a substance using electricity.It requires a liquid to conduct the electricity called the electrolyte.Electrolytes are often metal salt solutions made from the ore.The electrolyte has free ions. These conduct the electricity and allow the whole thing to work.As ions gain or loose electrons, they become atoms and molecules and are released.

Topic 3,1a

Metal extraction can be bad for the environment.People have to balance the social, economic and environmental effects.Most of the issues of mining ores are the same as quarrying limestone.So mining metal ores is good because: It provides jobs for local people                                                      It makes useful products.Bad for the environment because: It causes a lot of noise.                                               Scarring landscape and habitats.                                               Dangerous once shaft is abandoned.A lot of energy is used in the extraction process, so recycling metals is important.

Topic 3,1b mon 8th ALKENES + ETHANOL

Alkenes are hydro carbons which have a double bond between two carbon atoms in their chain.They are unsaturated because they can make ore bonds.The double bond can open up, allowing the two carbon atoms to bond with other atoms.You can test for an alkene by adding the substance to bromine water.An alkene will decolourise the bromine water.

Topic 3,1b

The first two alkenes are: 1) ethene, with 2 carbon atoms - C2H4                                         H           H                                             C = C                                          H        H2) propene, with 3 carbon atoms - C3H6                                         H   H       H                                    H - C - C = C                                         H            H

Topic 3,1b

Alkenes can be used to make polymers.Polymerisation is joining together lots of small alkane molecules (monomers) to form very large molecules - called polymers.E.G. many ethene molecules can be joined up to form poly(ethene) or "polythene".H           H    H          H   H           H                         H H H H H H H H H H    C = C           C = C          C = C         CATALYST     -C-C-C-C-C-C-C-C-C-C-  H        H      H         H     H        H                          H H H H H H H H H H MANY (ethene) MONOMERS                TO FORM...     A (polythene) POLYMER

Topic 3,1b

Different polymers have different physical properties.The physical properties of a polymer depend on what it is made from.They are also affected by the temperature and pressure of polymerisation.E.G. poly(ethene) made at 200c and 2000 atmospheric pressure is flexible          and low density. However, poly(ethene) made at 60c and few     atmospheric pressure with a catalyst is rigid and dense.Light, stretchable polymers are used to make plastic bags and tights.Waterproof coatings for fabrics are made of polymers.Tooth fillings and wound dressings are often made of polymers.Biodegradable packaging is made from polymers.Memory foam is a polymer that gets softer as it gets warmer.

Topic 3,1b

Polymers are cheap, but most don't rot - they're hard to get rid of.Most aren't biodegradable.If you bury them in a landfill site, they'll still be there years later.The best thing is to reuse them as many times as possible and recycle.Things made from polymers are usually cheaper than metal items.However, the more polymer products used up, the more expensive they'll get.One day there wont be enough oil for fuel and plastics and other uses.To decide how to use the oil that's left, we must look at (dis)advantages.

Topic 4,1a tue 9th PROPERTIES OF METALS

Metals are strong and bendy and are good conductors of heat + electricity.They have lots of everyday uses because:    Their strength and flexibility means they can be made into cars + bridges.    They are ideal to make something that heat needs to travel through.    They can be made into electrical wires because of their conductivity.

Topic 4,1a

Copper:good conductor of electricity.Hard and strong but can still be bent.Doesn't react with water.Aluminium:Corrosion resistant.Low density.Not very strong but forms strong alloys.Titanium:Low density.Very strong.Corrosion resistant.

Topic 4,1a

Although metals are very useful structural materials, some corrode when exposed to air and water.Because of this they need to be protected E.G, by painting.If metals corrode, they loose their strength and hardness.Metals get 'tired' when stresses and strains get put on them.This is known as metal fatigue and leads to them breaking.This can be very dangerous E.G. planes.

Topic 4,1a pt 2 ALLOYS

Pure metals aren't often very useful for certain jobs.Mixing two metals together to get the desired properties makes an alloy.E.G. pure iron is too bendy.Iron straight from a furnace is usually 96% iron, 4% impurities (carbon etc).This impure iron is called cast iron.It doesn't have many uses because it's brittle.So, most of the impurities are removed from the cast iron.This pure iron has a regular arrangement of identical atoms.These slide over each other making the iron soft and easily shaped.However this iron is far too bendy for most uses.

Topic 4,1a pt 2

Most iron is converted into steel - an alloy.Steels are formed by adding small amounts of carbon to the iron.E.G. low carbon steel (0.1% carbon) is easily shaped and used for car bodies.     High carbon steel (1.5% carbon) is very hard and inflexible and used for          blades for tools and bridges.     Stainless steel (chromium and nickel added) is corrosion resistant and          used for cutlery and containers for corrosive substances.

Topic 4,1a pt 2

Alloys are harder than pure metals.Different elements have different sized atoms.So, when a small element such as carbon is added to pure iron, the smaller carbon atom will upset the layers of iron atoms making it harder for them to slide over each other. So alloys are harder.Many metals in use today are alloys:Bronze = copper + tin.Cupronickel = copper + nickel.Many gold alloys.Many aluminium alloys.

Topic 4,1b tue 9th PLANT OILS

We can extract oils from plants.Some fruits and seeds contain a lot of oils.E.G. avocados and olives, brazil nuts, peanuts and sesame seeds.These oils can be extracted and used for fuel and food.To extract the oil:Crush the plant, press the plant, squash the oil out.Oil and crushed plant material are separated through centrifuge.Or solvents can be used to get oil out.Distillation refines oil and removes water, solvents and impurities.

Topic 4,1b

Vegetable oils are used in foods.It provides a lot of energy.There are other nutrients in vegetable oils.E.G oils from seeds contain vitamin e.They also contain essential fatty acids which the body needs for metabolism.Vegetable oil have benefits for cooking:Higher boiling points than water - cook faster.Gives foods a different flavour.Increases the energy we get from eating it.

Topic 4,1b

Vegetable oils can be used for fuels.Rapeseed oil and soy bean oils can be processed and turned into fuels.Vegetable oils provide a lot of energy they're really suitable as fuels.A particularly useful fuel is called bio diesel.It has similar properties to normal diesel - it burns in the same way.

Topic 4,1b

Unsaturated oils contain C = C double bonds.Oils and fats contain long chain molecules with lots of carbon atoms.Therefore they are either saturated or unsaturated.Unsaturated oils contain double bonds between some of the carbon atoms.So, an unsaturated oil will de-colourise bromine water.Mono-unsaturated fats contain one C = C double bond.Poly-unsaturated fats contain more than one C = C double bond.

Topic 4,1b

Unsaturated vegetable oils are liquid at room temperature.They can be hardened by hydrogenation: reacting them with hydrogen in the presence of a nickel catalyst at about 60 degrees.Hydrogenated oils have higher melting points than unsaturated oils.So they're more solid at room temperature.This makes them useful as spreads.Margarine is usually made from partially hydrogenated vegetable oils.Partially hydrogenated oils are often used in processed foods such as biscuits, this makes them cheaper and gives them a longer shelf-life.But partially hydrogenating oils produce transfats.These are very bad for you.

Topic 4,1b

Vegetable oils can affect health.Vegetable oils tend to be unsaturated, whereas animal fats are saturated.In general, saturated fats are less healthy than unsaturated fats.Cooking food in oil, whether it is saturated or unsaturated makes it more fattening.

Topic 5,1a wed 10th CRUDE OIL

Fractional distillation of crude oil:Crude oil is a mixture of hydrocarbons.A mixture is 2+ elements / compounds that aren't chemically bonded.Crude oil is a mixture of many different compounds.Most of the compounds are hydro carbon molecules.The different hydro carbon molecules in crude oil aren't chemically bonded.This means that they keep their original properties such as boiling points.The parts of a mixture can be separated out.Crude oil cam be split up by fractional distillation.

Topic 5,1a

Crude oil split by fractional distillation into separate groups of hydrocarbons.The fractioning column works continuously.Heated crude oil is piped in at the bottom.The vaporised oil rises up the column and the various fractions are constantly tapped off at different levels when they condense.

Topic 5,1a

The different fractions of crude oil have different uses.Its all down to their structure.Crude oil is mostly alkanes.Alkanes are chains of carbon atoms surrounded by hydrogen atoms.Different alkanes have chains of different lengths.The first four alkanes are methane, ethane, propane and butane.Methane (CH4)    H             Ethane (C2H6)     H                    H - C - H                           H - C - H                         H                                     HPropane (C3H6)   H                    H - C - H

Topic 5,1a

The different fractions of crude oil have different uses.Its all down to their structure.Crude oil is mostly alkanes.Alkanes are chains of carbon atoms surrounded by hydrogen atoms.Different alkanes have chains of different lengths.The first four alkanes are methane, ethane, propane and butane.

Methane  (CH4)      H                      H - C - H                           HEthane  (C2H6)      H   H                      H - C - C - H                           H   HPropane  (C3H8)     H   H   H                       H - C - C - C - H                            H   H   HButane  (C4H10)       H   H   H  H                       H - C - C - C - C - H                            H   H    H   

Topic 5,1a

Learning the basic trendsThe shorter the molecules, the more runny the hydro carbon is.The shorter the molecules, the more volatile the hydro carbon is (they turn into a gas at a lower temperature.)The shorter the molecule, the more flammable the hydro carbon.

Topic 5,1b wed 10th EMULSIONS

Emulsions can be made from oil and water.An emulsion is one liquid suspended in another liquid.You can have an oil-in-water emulsion - oil droplets suspended in water.Or a water-in-oil emulsion - water droplets suspended in oil.Emulsions are thicker than the original product.The more oil you've got, the thicker it is.Often used for food E.G. mayonnaise and whipped cream.Also used for substances such as body lotion.

Topic 5,1b

HOWEVER, oil and water often separate out. This is where emulsifiers come.Emulsifiers are a product with one part that's attracted to oil (hydrophobic).And one part that's attracted to water (hydrophilic).The hydrophilic end latches onto water molecules.The hydrophobic end latches on to oil molecules.Emulsifiers stop emulsions from separating.They give them a longer shelf life.They allow companies to produce food lower in fat.But some people are allergic to emulsifiers, E.G egg yolks etc.