OCR Gateway Chemistry C1

WHY ARE FOSSIL FUELS FINITE RESOURCES AND ARE NON-RENEWABLE

• finite resources are no longer being made or being made extremely slowly same as fossil fuels
• non-renewable resources are used up faster than they are formed same as fossil fuels

PROBLEMS ASSOCIATED WITH THE FINITE NATURE OF CRUDE OIL

• all the readily extractable resources will be used up in the future
• finding replacements is a huge issue
• conflict between making petrochemicals and fuels

REMEMBER CRUDE OIL IS A MIXTURE OF HYDROCARBONS

POTENTIAL PROBLEMS WITH TRANSPORTING CRUDE OIL

• damage to birds feathers causing death if spilled
• use of detergents to clean up oil slicks and consequent damage to wildlife

POLITICAL PROBLEMS ASSOCIATED WITH EXPLOITATION OF CRUDE OIL

• UK dependent on oil and gas from politically unstable countries
• future supply issues

FRACTIONAL DISTILATION

• crude oil is heated in a way that there is a temperature gradient (cold at the top and hot at the bottom)
• fractions containing mixtures of hydrocarbons are obtained
• fractions contain many substances with similar boiling points 
• fractions with low boiling points 'exit' from the top of the fractionating column 
• fractions with the high boiling points 'exit' at the bottom of the fractionating column

CRACKING IS A PROCESS THAT converts large alkane molecules into smaller alkane and alkene molecules. And a process that makes useful alkene molecules that can be used to make polymers. Cracking also helps match supply and demand.

FACTORS TO CONSIDER WHEN CHOOSING FUEL

• energy value
• Availablilty - theres not much point in choosing a fuel you can't get hold of
• Storage - if a fuel is flammable or explosive then it might be difficult to store it safely
• Cost - some fuels are expensive, but still good value in terms of energy content etc.
• Toxicity - some fuels are toxic, and some produce poisonous fuels when they burn
• ease of use - whether it lights easy, whether you can move it safely
• Pollution - e.g. will you be adding to acid rain and greenhouse effect...

THE AMOUNT OF FOSSIL FUEL BEING BURNED IS INCREASING BECAUSE...

• increasing world population
• growth of use in developing countries .e.g. India and China

WORD EQUATIONS THAT SHOW COMPLETE COMBUSTION

• Hydrocarbon + oxygen -> carbon dioxide + water (+ energy)

WORD EQUATION FOR INCOMPLETE COMBUSTION

• hydrocarbon + oxygen -> carbon dioxide + water + carbon monoxide + carbon (+ energy)

REMEMBER incomplete combustion is not safe and complete combustion is safer

GAS PERCENTAGES IN THE AIR

• 21% oxygen
• 78% nitrogen
• 0.035% carbon dioxide

EFFECTS OF HUMAN INFLUENCES ON THE COMPOSITION OF AIR

• deforestation
• population

CARBON CYCLE

• the carbon on Earth moves in a big cycle
• respiration, combustion and deacy of plants and animals add carbon dioxide to the air and remove oxygen
• photosynthesis does the opposite - it removes carbon dioxide and adds oxygen
• these processes should all balance out. However, humans have upset the natural carbon cycle, which has affected the balance of gases in the atmosphere.

EVOLUTION OF OF PRESENT DAY ATMOSPHERE

• original atmosphere came from gases escaping from the interior of the Earth
• photosynthesis by plants increased the percentage of oxygen until it reached today's level

ONE POSSIBLE THEORY TO HOW TODAY'S ATMOSPHERE HAS EVOLVED (BASED ON THE COMPOSITION OF GASES VENTED BY PRESENT DAY VOLCANIC ACTIVITY)

• degassing of early volcanoes producing an atmosphere rich in water and carbon dioxide
• condensing of water vapour to form oceans 
• dissolving of carbon dioxide in ocean waters 
• relative increase of nitrogen due to its lack of reactivity
• development of photosynthetic organisms
• increase in oxygen levels due to photosynthesis

IMPORTANT THAT ATMOSPHERIC POLLUTION IS CONTROLLED

• the build up of these pollutants can make life unhealthy and miserable for most humans, animals and plants.
• the number of cases of respiratory illnesses (e.g. asthma) has increased in recent years - specially on younger people. Many people blame atmospheric pollutiion for this, so efforts are being made to improve things

CATALYST CONVERTERS

• catalytic convertors on motor vehicles reduce the amount of carbon monoxide and nitrogen oxides getting into the atmosphere 
• the catalyst is usually made of platinum and rhodium
• they help unpleasant exhaust gases from the car react to make things that are less immediately dangerous
• they use equation:       carbon monoxide + nitrogen oxide -> nitrogen + carbon dioxide      or the symbol equation:          2CO            +         2NO      ->     N2     +        2CO2

HYDROCARBONS and SATURATED/UNSATURATED COMPOUNDS

• Hydrocarbons are compounds which contain only carbon and hydrogen atoms
• a saturated compound is when the compund only contains single covalent bonds between carbon atoms
• a unsaturated compund is when a compound contains at least one double covalent bond between carbon atoms
• alkanes are hydrocarbons which contain single covalent bonds only
• alkenes are hydrocarbons which contain a double covalent bond(s) between carbon atoms
• double bonds involve two shared pairs of electrons

USING BROMINE TO TEST FOR ALKENES

• bromine can be used to test for an alkene:
• bromine water is orange
• bromine water is decolourised
• explain the reaction between bromine and alkenes:
• addition reaction
• formation of colourless dibromo compound

 ADDITION POLYMERISATION

• polymerisation is a process in which many alkene monomer molecules react together to give a polymer which requires high pressure and a catalyst
• addition polymerisation in terms of unsaturated molecules: lots of unsaturated monomer molecules can open up their double bonds and join together to form polymer chains. This is called addition polymerisation 

PROPERTIES A POLYMER (PLASTIC) SHOULD HAVE IN ORDER TO BE USED FOR A PARTICULAR PURPOSE

• Strong and rigid - polymers such as high density polythene are used to make plastic milk bottles
• light, stretchable - polymers such as low density polythene are used for plastic bags and squeezy bottles. Low density polythene has a low melting point, so its no good for anything that'll get very hot
• PVC is strong and durable, and it can be made eiether rigid or stretchy. The rigid kind is used to make window frames and piping. The stretchy kind is used to make synthetic leather
• polystyrene foam is used in packaging to protect breakable things, and its used to make disposable coffee cups ( the trapped air in the foam makes it a brillinat thermal insulator)

REMEMBER that the atoms in plastics are held together by strong covalent bonds

RELATE THE PROPERTIES OF PLASTICS TO SIMPLE MODELS OF THEIR STRUCTURE

• plastics that have weak intermolecular forces between polymer molecules have low melting points and can be stretched easily as the polymer molecules can slide over one another
• plastics that have strong forces between the polymer molecules (covalent bonds or crossing bridges) have high melting points, cannot be stretched and are rigid

COMPARE THE PROPERTIES OF NYLON AND GORE-TEX

• nylon is tough, lightweight, keeps water out and keeps UV light out but does not let water vapour through it which means that sweat condenses 
• Gore-tex has all of the properties of nylon but is also breathable - this is really good for outdoor use because helps people cope with sweat because if you sweat in the material, the water vapour can escape - so no condensation

WHY ARE GORE-TEX TYPE MATERIALS WATERPROOF YET BREATHABLE?

• because gore-tex is nylon laminated with PTFE / polyurethene membrane
• holes in membrane are too small for water to pass through but are big enough for water vapour to pass through
• membrane is too fragile on its own and so is combined with nylon

CHEMISTS ARE DEVELOPING NEW TYPES OF POLYMER BECAUSE...

• they want polymers that can dissolve
• they want polymers that are biodegradable

ISSUES RELATED TO THE DISPOSAL PROBLEMS

• using landfill is a waste of plastics and landfills can fill up really quickly
• you cant burn plastics to get rid of them because they can release gases that may be acidic and poisonous
• most polymers arent 'biodegradable' so they just rot.

REMEMBER that protein molecules in eggs and meat change shape when eggs and meat are cooked: this is called denaturing

EXPLAIN WHY TEXTURE OF EGG OR MEAT CHANGES WHEN IT IS COOKED:

• Shape of protein molecules permanently changes.

EXPLAIN WHY POTATO IS EASIER TO DIGEST IF IT IS COOKED:

• cell walls rupture resulting in loss of rigid structure and a softer texture
• starch grains swell up and spread out

REMEMBER describe emulsifiers as molecules that have a water loving (hydrophillic) part and an oil or fat loving (hydrophobic) part

EMULSIFIERS HELPS TO KEEP OIL AND WATER FROM SEPERATING:

• hydrophillic end bonds to water molecules
• hydrophobic end bonds with oil or fat molecules

REMEMBER that alcohols react with acids to make an ester and water

PROPERTIES THAT PERFUMES NEED TO HAVE

• easily evaporates so that the perfume particles can easily reach the nose
• non-toxic so it does not poison you
• does not react with water because otherwise the perfume would react with perspiration
• does not irritate the skin otherwise the perfume could not be put directly onto the skin
• insoluble in water so it cannot be washed off easily

VOLATILITY IN TERMS OF KINECTIC THEORY

• in order to evaporate particles need sufficient energy to overcome the attraction to other molecules in the liquid
• only weak attraction exists between particles in the liquid perfume so it is easy to overcome this attraction

REMEMBER that esters can be used as solvents. Describe a solutioin as a mixture of solvent and solute that does not seperate out

EXPLAIN WHY WATER CAN'T DISSOLVE NAIL VANISH

• attraction between water molecules is stronger than attraction between water molecules and particles in nail varnish
• attraction between particles in nail varnish is stronger than attraction between water molecules and particles in nail varnish

WHY IS ANIMAL TESTING BANNED IN THE EU

• people think that it is wrong to cause suffering to animals just to test the safety of a cosmetic - especially when the results of the animal tests might not be conclusive

REMEMBER describe paint as a colloid where the particles are mixed and dispersed with particles of a liquid but are not dissolved 

WHY DONT COMPONENTS OF A COLLOID SEPERATE

• because the particles are so small. They don't settle out at the bottom.

HOW DOES MOST PAINT DRY

• paints are applied as a thin layer 
• the solvent evaporates
• describe emulsion paints as water based paints that dry when the solvent evaporates

HOW DOES OIL PAINT DRY

• the solvent evaporates 
• the oil is oxidised by atmospheric oxygen

THERMOCHROMIC PAINTS

• thermochromic pigments change colour when heated
• they are usually ysed on baby spoons to tell if the food is too hot

WHY DO PHOSPHORESCENT PAINT GLOW IN THE DARK

• they absorb and store energy
• then release it as light over a period of time

REMEMBER that phsphorescent pigments are much safer than the alternative radioactive substances