Chemistry Revision, C1,C2,C3

C1,C2,C3

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Crude Oils, C1

Crude oil is found in the earths crust. it can be pumped to the surface,

Crude oil can be used a source of fuel or chemicals, but is being used up much faster than it is being produced.

Fossil Fuels,

  • Formed naturally over millions of years
  • Finite(being used up much faster than its being replaced) and non renwable.
  • All easily extracted


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Fractional Distilation C1.

Crude oil is a mixture of hydrocarbon. (A hydrocarbon is a molecule that contains only hydrogen and carbon atoms).

Different hydrocarbons have different boiling points which means that crude oil can be seperated into useful parts that contain mixtures of hydrocarbons with similar boiling points, The process used is fractional distillation.

The crude oil is heated in a fractioning column. the column has a temperature gradient, which makes the bottom hotter than the top.

  • Fractions with low boiling points leave at the top of the fractionating column.
  • Fractions with high boiling points leave at the bottom of the fractioning colimn.
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Cracking C1.

Hydrocarbon molecules can be described as alkanes or alkenes.

Large alkane molecules can be broken down into smaller more usefull, alkane and alkene molecules.

The process is called cracking, and needs catalyst.

Cracking is used to make more petrol from naphtha, it can also be used to make alkene molecules that may be used to make polymers(a polymer is a plastic)

Forces between molecules.

In a hydrocarbon molecule there are:

  • Strong covalent bonds between the atoms in the molecule
  • Weak intermolecular forces ( forces of attraction between molecules)
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Carbon Fuels, C1

Combustion

When fuels react with oxygen (in the air) they burn and release useful heat energy, This is called combustion, and it needs a plentiful supply of oxygen.

Incomplete Combustion

When fuels burn without enough oxygen incomplete combustion happens. Incomplete combustion of a hydrocarbon produces carbon monoxide (a poisonous gas). When very little oxygen is present, incomplete combustion of a hydrocarbon produces carbon (soot) and water.

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C1 Making Polymers

Hydro Carbons

Hydrocarbons are compounds that contain only carbon and hydrogen:

  • Carbon atoms can make four bonds each,
  • Hydrogen atoms can make one bond each
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C1 Alkanes+Alkenes

Alkanes

When a hydrocarbon chain has only single covalent bonds, it is called an alkane. All of the carbon atoms make four single covalent bonds, Alkanes are normally described as saturated.

Alkenes

When a hydrocarbon chain has one or more double carbon-carbon (c=c) covalent bonds, its called an alkene, Double bonds have two shared pairs of electrons. Alkenes are normally described as unsaturated.

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C1 Emulsifiers

Emulsions

Vegetable oils do not dissolve in water. If oil and water are shaken together, tiny droplets of one liquid spread through the other liquid, forming a mixture called an emulsion.

Emulsions are thicker (more viscous) than the oil or water they contain. This makes them useful in foods such as salad dressings and ice cream. Emulsions are also used in cosmetics and paints. There are two main types of emulsion:

  • oil droplets in water (milk, ice cream, salad cream, mayonnaise)
  • water droplets in Emulsifier molecules have two different ends:
    • a hydrophilic end - 'water-loving' - that forms chemical bonds with water but not with oils
    • a hydrophobic end - 'water-hating' - that forms chemical bonds with oils but not with water.
    oil (margarine, butter, skin   cream, moisturising lotion)
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C1 Emulsifiers Continued

  • (http://www.bbc.co.uk/schools/gcsebitesize/science/images/59_emulsifiers.gif)
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C1 Smells

Solutions

  • Soluble substances are substances that dissolve in a liquid e.g. nail varnish is soluble in ethyl ethanoate (nail varnish remover)
  • Insoluble substances are substances that dont dissolve in a liquid e.g. nail varnish is insoluble in water.
  • A solvent is the liquid into which a substance is dissolved e.g. nail varnish remover is a solvent (an ester can be used as a solvent)
  • A solute is the substance that gets dissolved e.g. the nail varnish is a solute
  • A solution is what you get when you mix a solvent and a solute ( it will not separate out)
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C1 Paints and Pigments

Paint

Paint is a colloid , Colloids are made of small, solid particles that are mixed well (dispersed but not dissolved) with liquid particles.

Paint is a mixture of:

  • Pigment-a substance that gives paint its colour,
  • Binding medium-an oil that sticks the pigment to the surface that its being painted onto
  • Solvent-thins the thick binding medium and makes it easier to coat the surface
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C1 Paints and Pigments

Paint

Paint is a colloid , Colloids are made of small, solid particles that are mixed well (dispersed but not dissolved) with liquid particles.

Paint is a mixture of:

  • Pigment-a substance that gives paint its colour,
  • Binding medium-an oil that sticks the pigment to the surface that its being painted onto
  • Solvent-thins the thick binding medium and makes it easier to coat the surface
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C2 Electrolysis

Electrolysis

Electrolysis uses an electric current to break down compounds into simpler substances, In electrolysis electricity is passed through a liquid or a solution called electrolyte e.g. copper, sulfate solution, to make simpler substances.

  • The anode (positive electrode) is made of impure copper  ( Cu - 2e- = Cu2+ )
  • The cathode (negative electrode) is made of  pure copper. (Cu2+  + 2e- =Cu)
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C2 Alloys

Alloys

An alloy is a mixture of a metal with another element ( usually another metal) Bronze and steel are alloys. Alloys improve the properties of a metal and make them more useful, they often harder and stronger than the pure metal. E.G.

  • Amalgam (made using mercury) is used for fillings in teeth
  • Solder (made of lead and tin) is used to join wires
  • Brass (made of copper and zinc) is used in door handles, coins and musical instruments
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C2 Rusting Conditions

Rusting Conditions

Rusting is an example of an oxidation reaction (a reaction where oxygen is added to a substance.

Rusting Needs

  • Iron
  • Water
  • Oxygen (air)
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C2 Ammonia

Ammonia

Ammonia (NH3) is an alkaline gas made from nitrogen and hydrogen. it can be used to make:

  • Nitric acid
  • fertilisers (cheap fertilisers are very important in helping to produce enough food for the growing world population)

The reaction which makes ammonia is a reversible reaction, so nitrogen and hydrogen can form ammonia, and ammonia can decompose to make hydrogen and nitrogen.

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C2 The Haber process

Ammonia is made on a large scale in the haber process, the reactants are:

  • nitrogen (from the air)
  • hydrogen (from natural gas or the cracking of crude oil)

nitrogen  +  hyrdrogen  (reversable sign) ammonia

Economics of the haber process

For the haber process:

  • a low temperature increases yield but the reaction is too slow
  • a high pressure increases yield but becomes more expensive as yield increases.
  • a catalyst incraeses the rate of reaction but doesnt change the percentage yield.
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C2 Acids, Bases and indicators.

Neutralisation

Metal oxides and metal hydroxides are bases, when they are added to acids in the correct amounts, theycancel each other out. This is called neutralisation because the resulting solution has a neutral pH of 7.

Acid + base ------> salt + water

Acids can also be neutralised by carbonates to produce a salt, water and carbon dioxide gas.

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C2, Fertilisers and crop yield.

Fertilisers

Fertilisers are chemicals that give plants essential chemical elements needed for growth, fertilisers:

  • make crops grow faster and bigger
  • increase the crop yield

As world population rise, fertilisers can increase food supply but can also cause problems such as the death of animals in water ways, this is known as eutrophication.

The three main elements found in fertilisers:

  • Nitrogen
  • Phosphorus
  • Potassium
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C2, Electrolysis

Electrolysis

When concentrated sodium chloride solution is electrolysed, the electrodes must be made from inhert materials as the products are very reactive this process forms:

  • sodium hydroxide in the solution
  • hydrogen at the cathode (negative electrode)
  • chlorine at the anode (positive electrode) 
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Comments

rose

this is really useful for quick notes thanks :D

Caitlin Ward

This is really helpful and is based on the things I find the most difficult thanks!

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