OCR GCSE Chemistry C1a-h

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C1a - Making Crude Oil Useful

Hydrocarbon = contains hydrogen and carbon atoms only (Key word examiners look for)

3 types of fossil fuels:

Crude Oil

Coal

Natural Gas

3 problems associated with the finite nature of crude oil:

All readily extractable resources used up

Finding replacements

Conflict between making petrochemicals and fuels

Hydrocarbon with:

1 Carbon = Methane (MY)

2 Carbons = Ethane (ELEPHANT)

3 Carbons = Propane (POOS) IN LPG

4 Carbons = Butane (BRICKS) IN LPG

5 Carbons = Pentane (PLEASE)

6 Carbons = Hexane (HELP)

Fractions in crude oil (from top of column to bottom):

LPG (LITTLE)

Petrol (PURPLE)

Paraffin (PUFFINS)

Diesel (DANCE)

Heating Oil (HOME)

Lubricating Oil (LEAVING)

Fuel Oil (FOOTPRINTS)

Bitumen (BEHIND)

Non-renewable = resource is being used up faster than it can be formed (e.g. crude oil)

Finite = Resource is no longer being made or is being made extremely slowly

Smaller Fractions:

Smaller molecules have weaker intermolecular forces

Require less energy to break

Lower boiling points

Larger Fractions:

Larger Molecules have stronger intermolecular forces

Require more energy to break

Higher boiling points

During boiling the intermolecular forces between molecules break, but the covalent bonds do not.

Political problems associated with the exploitation of Crude Oil:

UK dependent on Oil from politically unstable countries

Future supply issues

Environmental problems involved in the transportation of Crude Oil:

Detergents used to clean up Oil Slicks can cause damage to wildlife

Damage to bird's feathers causing death

Alkene = carbon-carbon double bond (un-saturated) (Test for an alkene = bromine water will decolourise) CnH2n

Alkane = no carbon-carbon double bond (saturated) Cn H2n+2

Cracking:

Helps to make more Petrol

Conditions required are a high temperature and a catalyst

Converts large alkane molecules into smaller alkane and alkene molecules

Makes useful alkene molecules that can be used to make polymers

Long un-useful hydrocarbons (in high supply yet low demand) are broken down into smaller hydrocarbons (in low supply yet high demand)

e.g. Bitumen to Petrol

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C1b - Using Carbon Fuels

Combustion = When fuels react with oxygen in the air and release useful heat energy

Incomplete combustion = When fuels burn without enough oxygen and some heat energy is released, but not as much as complete combustion

Complete Combustion of Methane: Bold = subscript

Methane (CH4) + Oxygen (2O2) →Carbon Dioxide (CO2) + Water (H2O)

Incomplete Combustion of Methane:

Methane (2CH4) + Oxygen (3O2) →Carbon monoxide (2CO) + Water (H2O)

7 Factors of fuels in order to choose the best for a particular purpose: (TEACUPS / ACEPETS)

Energy Value

Availability

Ease of storage

Cost

Toxicity

Pollution

Ease of Use

The blue Bunsen flame releases more energy than the yellow flame.

Increasing amount of fossil fuels being burnt because of:

Increasing world population

Increased use in developing countries, such as China

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C1c - Clean Air

How does _____ effect the level of carbon dioxide in the air?

Combustion? Increases

Respiration? Increases

Deforestation? Increases

Photosynthesis? Decreases

Increasing population? Increases

The 4 components of air:

Oxygen (21%)

Nitrogen (78%)

Water Vapour (0.035%)

Carbon Dioxide

These levels are approximately constant.

Balanced symbol equation for how a catalytic converter removes carbon monoxide from exhaust fumes:

2CO + 2NO →N2 + 2CO2

Possible theory for how the present day atmosphere evolved over millions of years:

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

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C1d - Making Polymers

Covalent bond = a shared pair of electrons

Double Covalent bond = 2 shared pairs of electrons

The addition polymerisation process:

Many alkene monomer molecules react together to give a polymer which requires high pressure and a catalyst

Why does bromine water decolourise in the presence of an alkene?

An addition reaction occurs that forms a colourless dibromo compound

Why is Methane/Ethane/Propane/Butane/Pentane/Hexane an alkane?

It only contains single covalent bonds between carbon atoms

Unsaturated = a compound which contains at least one double covalent bond between carbon atoms

Saturated = a compound which contains only single covalent bonds between carbon atoms

Formation of a polymer:

Many small molecules (monomers) join together in a polymerisation reaction

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C1e - Designer Polymers

Environmental and economic issues related to the use and disposal of polymers:

Uses up valuable land in landfill

Can ham/kill wildlife

Burning release toxic gases

Burning is a waste of resources

What properties of polyethene allows it to be used for plastic bags?

Light

Flexible

Easily Moulded

Can be easily printed on

What properties of polyester allows it to be used for waterproof jackets?

Lightweight

Waterproof

Tough

Can be coloured

Blocks UV light

What properties of polystyrene allows it to be used to hold hot liquids?

Light

Poor conductor of heat

What properties of nylon allows it to be used for tents?

Lightweight

Waterproof

Tough

Blocks UV light

Plastics that have weak intermolecular forces have what properties?

Low melting points

Can be stretched easily as the polymer molecules can slide over one another

Plastics that have covalent bonds or cross-linking bridges have what properties?

High melting points

Cannot be stretched and are rigid

Main properties of nylon:

Tough

Lightweight

Keeps water and UV light out, but does not let water vapour through it which means that sweat condenses

Main properties of Gore-Tex:

Same as nylon + is breathable

Membrane = PTFE, not used on its own because its too fragile

Holes in membrane are too small for water to pass through but are big enough for water vapour to pass through

Methods of disposing polymers:

Use of land-fill sites

Burning

Recycling

Why are chemists developing...

polymers that bio-degrade? so that they can degrade faster in landfill

polymers that dissolve? so that they can increase their range of uses (e.g. dishwasher tablets)

Non-biodegradable = Will not decay or decompose by bacterial action

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C1f - Cooking and food additives

Emulsifiers = prevent oil and water from separating (e.g. In mayonnaise)

Hydrophilic head (binds to water molecules) and Hydrophobic tail (binds to oil molecules)

Food is a chemical change because:

A new substance is formed

The process cannot be reversed

An energy change takes place

Why is a potato easier to digest if cooked?

Cell walls rupture resulting in loss of rigid structure

Starch grains swell up and spread out

Why does the texture of an egg change when cooked?

Protein molecules permanently change shape and denature

Function of Antioxidants = stops food reacting with oxygen and gives it a longer life

Food colouring, Flavour enhancers, Antioxidants and Emulsifiers are all examples of food additives

Sodium Hydrogencarbonate is heated = Thermal decomposition, results in sodium carbonate, carbon dioxide and water

(Sodium Hydrogencarbonate → Sodium Carbonate + Carbon dioxide + water / 2NaHCO3 → Na2CO3 + CO2 + H2O)

How does baking soda help cakes to rise?

Sodium hydrogencarbonate thermally decomposes, which produces carbon dioxide, which helps cake to rise

Chemicals in food affected by cooking:

Proteins

Carbohydrates

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C1g - Smells

Soluble substance = Dissolves in a liquid (e.g. nail varnish is will dissolve in ethyl ethanoate)

Insoluble substance = Doesn't dissolve in a liquid (e.g. nail varnish does not dissolve in water)

Volatile = Evaporates easily

Solvent = The liquid in which a substance is dissolved (e.g. ethyl ethanoate)

Solute = The substance that gets dissolved

Solution = Result of mixing a solvent and a solute

Why does nail varnish not dissolve in water?

The attraction between water molecules and the attraction between nail varnish molecules is stronger than the attraction between water molecules and nail varnish molecules

How to make an ester:

(A family of compounds often used as perfumes and in solvents)

React an alcohol with an organic acid

Another name for manufactured perfumes = Synthetic perfumes

Main necessary properties of perfumes:

Smell Nice

Evaporate easily

Not be Toxic

Non-irritant

Insoluble

Not reactive with water

Why are perfumes volatile?

The molecules of perfume are held by weak forces of attraction, the molecules with lots of energy can easily overcome these weak forces and escape

Disadvantages of animal testing:

Cruel to animals

Different body chemistry so test results may be invalid

Advantages of animal testing:

Prevent harming humans

Test if medicines are safe

New drugs have to be tested to make sure they are safe:

The drugs are tested using computer models and human cells grown in the laboratory.

Drugs that pass the first stage are tested on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects.

Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check they are safe. The substances are then tested on people with the illness that the drugs are designed to treat to ensure that they are safe and work properly.

Perfumes from natural sources:

Lavender

Musk

Rose

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C1h - Paints and Pigments

Paint = a colloid, the particles of pigment are mixed and dispersed with particles of a liquid but are not dissolved, they do not separate out because they are too small

Oil based paint = Pigments are dissolved in an oil, which may be dissolved in a solvents.

Oil Paints dry in 2 steps:

The solvent evaporates

The oil is oxidised by atmospheric oxygen

Emulsion Paints dry in 2 steps:

Paints are apllied as thin layer

The solvent (water) evaporates

A thermochromic paint changes colour when heated or cooled, acrylic paint can be added to thermochromic pigments to give thermochromic paints more colour changes

Uses for thermochromic pigments:

Babies bath toys

Kettle

Thermometers

A phosphorescent pigment can glow in the dark, phosphorescent pigments are used rather than radioactive alternatives because they are much safer

A phosphorescent pigment glows in the dark because they absorb and store energy and then release it as light over a period of time

3 components of paint:

Binder = Sticks pigment in paint to surface

Solvent = Thins the paint and makes it easier to spread

Pigment = Gives the substance its colour