Cooking Why do we cook food? When food is cooked... High temperature kills harmful bacteria Texture of food is improved Flavour of food is enhanced Food is easier for the body to digest When food is cooked... It cannot return to its raw state The change is irreversible An energy change takes place in the food

Cooking Proteins Cooking is chemical change because a new substance is made Meat and eggs are good sources of proteins Proteins are large molecules that have definite shapes A protein is a long molecule that has four types of structure - Primary- This is the sequence of amino acids in a protein chain Secondary- This is when a protein coils into a helix shape Tertiary- This is when a protein has a folding structure as new bonds are formed. Quaternary- This is when more than one protein joins to form a large protein such as haemoglobin

Cooking Baking powder Baking powder is a chemical called sodium hydrogen carbonate When heated it decomposes to give sodium carbonate, carbon dioxide and water. Sodium hydrogen carbonate Sodium carbonate + Carbon dioxide + water 2NaHCO3 Na2CO3 + H2O + CO2

Cooking Testing for carbon dioxide Potatoes Limewater turns from colourless to milky white if carbon dioxide is present. Potatoes When a potato is cooked its cell walls breakdown and starch grains burst. This makes the potato easier for the body to digest.

Food Additives The Four Main Types Of Food Additives Are: Antioxidants Colours Emulsifiers Flavour Enhancers Antioxidants stop food from reacting with oxygen and turning bad An antioxidant is used to prevent apples from turning brown. It is also called ascorbic acid (vitamin c) Every additive has its own reference number vitamin c-E300

-Soiling happens when a food reacts with oxygen, bacteria or mould. -Food additives are added to preserve food so that it can be distribute around the country or go to other countries without spoiling -Soiling happens when a food reacts with oxygen, bacteria or mould. -Additives are also added to give a different sensory experience. They are also used to enhance the colour or flavour of food

Intelligent Packaging Intelligent packaging is another method used to stop food spoiling Active packaging: Actively changes the condition of packaged food to extend its life while maintaining the quality of the products Intelligent packaging: Monitors the condition of packaged food and gives information on the quality of the packaged food using sensors and indicators

CI REVISION What makes a good perfume? A good perfume: Evaporates easily Is non Toxic Does not react with water Does not irritate the skin Is insoluble in water Perfumes can be made using natural substances or can be made synthetically. 9

Why do perfumes need certain qualities? Making a Perfume To make a perfume, a chemical called an ester is made. An alcohol mixed with an acid makes an ester. Ethanol+ethanoic acid+Ethyl ethanoate Why do perfumes need certain qualities? Evaporates Easily: perfume particles reach nose. Non Toxic: Will not poison people No water reaction: perfume wont react with perspiration. Does not irritate skin: so perfume can be sprayed onto skin Insoluble in water: perfume is not washed off skin Volatile perfumes are liquids that have energetic fast moving particles at room temperature, there is only a weak attraction between particles, so forces of attraction between molecules are easily overcome 10

Solubility A substance that dissolves in water is soluble. The substance is called the solute and the liquid that it dissolves in is called the solvent. A substance that does not dissolve in liquid is called insoluble. Solutions A solution is a solute and a solvent that do not separate. Esters can be used as solvents and solvents can be used as cleaners. Cosmetics must not cause rashes or itchiness, or cause skin damage or other life threateing illnesses, i.e cancer. Some people say testing on animals is bad as the animals may be harmed, or there are other effective ways of testing things. Some people say that testing on animals is ok because, they think the animals reaction would closely mimic the humans or it makes them feel safer. 11

Attraction between particles Diffusion Diffusion is the movement of particles from an area of high concentration to an area of low concentration. Evaporation Liquid particles are weakly attracted to each other. When some particles increase their kinetic energy, the weak forces are overcome and particles escape. Attraction between particles Water does not dissolve nail varnish because the force of attraction between two water molecules is stronger than that between a water and a nail varnish molecules. Also the force of attraction between two varnish molecules is stronger than between a varnish molecule and a water molecule. 12

Chemistry Revision Crude oils...

What is crude oil ? Crude oil is formed from the buried remains of plants and animals- it is a fossil fuel.(Millions of years of pressure and high temperature causes the remains to turn to crude oil which can be drilled up and parts of it used for medicne fuels and lots of other things!) (the complicated ways of saying this... Crude oil is an occuring flammable liquid found in rock formations, in the eart made of a mixture of hydro-carbons =] )

Fractional Distillation The low down- Separating parts in a mixture. Crude oil is a mixture of hydrocarbons of different sized molecules , hydrcarbons are basically fuels such as petrol and diesel, they are made of just carbon and hydrogen, the bigger and longer the molecules, the less runny the hydro carbon...And the stronger the intermoleculer forces between the molecules, so alot of energy is needed to seperate the molecules so the boiling point is higher. So fractional distilation splits up crude oil into seperate fractions. The shorter the molecules the lower the themperatuere it condenses!!

Cracking Cracking is splitting up long chained hydrocarbons. Cracking is a process that turns the long chain hydrocarbons into shorter molecules which are more useful. Cracking is a form of thermal decompostition, which means just breacking down molecules into simpler molecules by heating them A lot of longer molecules produced from f.d are cracked into smaller ones because thes moree in demand like petrol and parrifin. Cracking also produces alkanes which are needed to make plastics. A catalyst is used to speed up reaction and make it happen

C1e- Making Polymers

C----------C----------C----------C Polymers Plastic is a polymer. We use plastic as a material in are everyday lives. A polymer is a big molecule which is made up of monomers. There are lots of different polymers such as: ethene, styrene, methene and propene. Polymerisation when lots of monomers are connected to make a polymer the reaction is called polymerisation. If all of the monomers are the same then it is called additional polymerisation and loads of them are joined. For polymerisation there has to be high pressure and a catalyst for it to work best. This will cause the double bond joining the two to break. Each of the separate atoms will then need to rejoin with another molecule with needs to join with another and so on. H H H H I I I I C----------C----------C----------C

Hydrocarbons Hydrocarbons are made from hydrogen and carbon. If it contains an additional atom then it is not a hydrocarbon. A Hydrocarbon is named according to the number of bonds and the number of carbon atoms. Polymers Polymers are made from hydrocarbons which have a double bond between two carbon atoms. They are either alkenes or alkanes depending on whether it is saturated or not. Saturation Bromine solution is orange and is used to test for unsaturation. If an alkene is present it will turn clear because of the reaction that takes place with the alkene to produce a new compound. If it is an Alkane then it does not react therefore stays orange.

Alkenes and Alkanes Hydrocarbons are compounds made from alkenes (which are unsaturated) and alkanes (which are saturated). Alkenes can act as a monomer under heat, pressure and with use of a catalyst. The formula of a alkene is ‘CnH2n’ and the formula for an alkane is ‘CnH2n+2’. If a Hydrocarbon ends in ‘ene’ then it is an alkene, if it ends with ‘ane’ then it is an alkane. Here are some useful hydrocarbons: Methane/- Ethane/Ethene Propene/Propane Butane/Butene

C1F Designer polymers Uses of polymers Different things are made of different polymers. Each polymer is chosen for its job. For example PVC poly(vinylchloride) Polymer Property 1 Property 2 Use PVC poly(vinylchloride) Waterproof Flexible Raincoats Poly(ethene) Plastic bags Poly(styrene) Insulates Absorbs shock Packaging Poly(propylene) strong ropes

More on breathable polymers GORE-TEX is a material that is waterproof and flexible but it is also breathable unlike PVC Nylon is used to make coats as it is tough, light weight and waterproof. The problem is that it doesn’t let water vapour out. Nylon GORE-TEX waterproof flexible Non-breathable breathable More on breathable polymers wind Water vapour from sweat is small enough to pass through Water droplets don’t pass through the membrane as they are too big Wind cannot pass through as it gets lost in the membrane The inner layer of the clothing is made with PTFE (polytetrafluoroethene)

Biodegradable polymers Polymers can be disposed: In landfill sites - by burning By recycling Problems of non-biodegradable polymers are: Difficult to dispose of Cause litter Use Polymer Other Material Contact lens Wet on the eye Dry on the eye Teeth filling Attractive Looks metallic Wound dressing waterproof Gets wet Biodegradable polymers Scientists are developing addition polymers that are biodegradable. They are easily disposed of. Problems of non-biodegradable polymers Disposal by burning or landfill sites wastes valuable resources Hard to sort different polymers so it is hard to recycle. Landfill sites get filled quickly and waste valuable land Burning waste produces toxic gas

Stretchy polymers and rigid polymers Atoms of the monomers are held together by Intramolecular bonds Two chains of a polymer are held together by intermolecular forces. They are week. Intermolecular forces of attraction are week monomer Intramolecular bonds are strong Week forces of attraction Pulling force Polymer stretches Pulling force Rigid polymer Strong bonds

Using Carbon Fuels

Comparing Fuels A fuel is chosen because of its characteristics. Energy value, availability, ease of use, storage method, cost, toxcity, pollution caused. Burning hydrocarbon fuels produces energy, fuel + oxygen carbon dioxide + water. Fuel burns in oxygen to give carbon dioxide and water. Limewater is used to test for carbon dioxide. White copper sulphate powder is used to test for water, which is produced as steam.

Different fuels are chosen for different jobs. Characteristic Coal Petrol Energy value High Availability Good Storage Bulky and dirty Volatile Cost Toxicity Produces acid fumes Produces less acid fumes Pollution caused Acid rain, carbon dioxide, soot Carbon dioxide, nitrous oxides Ease of use Easier to store as an energy source for power stations Flows easily around an engine so makes a good energy source for a car.

Combustion Complete combustion occurs when a fuel burns completely in air, a fuel such as methane uses oxygen in the air to produce products. Methane + oxygen = carbon dioxide + water. In complete combustion more energy is released than in incomplete combustion. Incomplete combustion occurs when a fuel burns in limited oxygen. The products are carbon monoxide and water. Complete combustion is better because; less soot is made, more heat is released, toxic carbon monoxide gas isn’t produced.

More on complete combustion Methane is a common used hydrocarbon fuel. The formula for methane is CH4. Complete combustion can be shown by the equation, CH4 + 2O2 = CO2 + 2H2O.

Energy Exothermic reactions When energy is transferred out into the surrounding area it is exothermic. Exothermic reactions cause a temperature increase as they are taking in more energy. exothermic makes bonds When energy is taken in form the surrounding area it is endothermic. Endothermic reactions cause a temperature decrease. Because it is losing energy. Endothermic reactions are bond making reactions.

You can calculate the energy transferred using this formula: Something burning with a blue flame has plenty of oxygen, and something burning with a yellow flame has little oxygen. This is called incomplete combustion. You can find the mass of fuel burnt by taking the mass after burning away from the mass before burning. You can calculate the energy transferred using this formula: You can calculate the energy output of a fuel using this formula: Energy transferred = mass of water x 4.2 x temp change Energy per gram = energy supplied/mass of fuel burnt