Chemistry

• Yield


  Mass of product a reaction produces
• Percentage of gases in the air


  Nitrogen- 78.1

  Oxygen- 21

  Argon- 0.9

  Carbon dioxide- 0.04
• Burning magnesium with oxygen


  Bright white flame.

  Powdery ash of magnesium oxide not very soluble but some dissolve to form an alkaline solution.
• Burning sulfur with oxygen

  Blue flame.

  Poisonous, colourless sulfur dioxide gas which dissolves in water to form sulfurous acid.
• Burning hydrogen in oxygen


  Pale blue flame.

  Water is produced.
• Metal oxides


  Ionic compound containing O2- ions.

  Basic oxides, react with acids to form salts.

  Usually insoluble in water, those that are form alkaline solutions (OH- ions).
• Non metal oxides


  Covalent compounds.

  Usually acidic oxides, react with bases to form salts.

  Soluble in water and form acidic solutions (H+) ions.
• Carbon dioxide


  Colourless gas.

  Produced when fossil fuels are burnt.

  Greenhouse gas.

  Increase in atmospher can lead to rising sea levels, more extreme weather, polar ice caps could melt.
• Group 1- alkali metals


  Increase in reactivity.

  Melting, boiling point decreases.

  Density increase.

  React rapidly with air to form metal oxide coatings.

  React with water to produce alkali metal hydroxide and hydrogen.

  Form com with 1+ metal ion.

  White/colourless compounds that dissolve to produce colourless solutions.
• Group 7- halogens


  Physical state: F2- yellow gas, Cl2- green gas, Br2- red liquid->orange vapour, I2- grey solid-> purple vapour.

  Diatomic molecule.

  Form HX compounds (HF) with hydrogen, dissolve to acids.

  Less reactive down the group.

  Coloured, poisonous vapours.

  Form X- (F-) ions in ionic compound.
• Reactivity series

  Potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold
• Redox reactions

  Loss of electrons- oxidation

  &

  Gain of electrons- reduction
• Sacrificial protection 


  Preventing rusting by using a more reactive metal. This metal undergoes oxidation instead.
• pH scale

  1-14, 0-3, 4-6, 7, 8-10, 11-14

  Red->orange->green->blue->purple

  strong acid->weak acid->neutral->weak alkali->strong alkali Hydrochloric acid, ethanoic acid, sodium chloride, ammonia, sodium hydroxide
• Indicators in acids

  Litmus- red

  Methyl orange- red

  Phenolphthalein- colourless

  Universal indicator- red
• Indicators in alkali

  Litmus- blue

  Methyl orange- yellow

  Phenolphthalein- pink

  Universal indicator- blue
• What ions does pH measure?

  H+, hydrogen
• Alkalis are a source of OH- ions
• Reaction between acid and alkali ions

  H-(aq)+OH-(aq)->H2O(l)
• Addition reaction


  At least 2 molecules combine to form a larger molecule.
• Alkanes


  CnH2n+2

  Most common hydrocarbon found in crude oil. C-C and C-H bonds
• Alkenes


  CnH2n

  Hydrocarbons with a double carbon bond causing them to be unsaturated so more reactive and very versatile
• Biodegradable

  Able to be broken down by living organisms
• Combustion

  Burning of a substance.

  Burning hydrocarbon fuels release energy.

  Complete combustion of hydrocarbon produces water and carbon dioxide.
• Cracking

  Breaking down larger hydrocarbons to produce smaller more useful molecules.

  Catalytic or steam cracking.
• Homologous series

  A series of compounds with the same functional group and similar chemical properties.
• Incomplete combustion

  Combustion carried out with insufficient oxygen. Can lead to the production of toxic carbon monoxid.
• Polymer

  Large long-chain molecules made up of lots of small monomers joined by covalent bonds
• Saturated hydrocarbon

  Hydrocarbon containing only single bonds between carbon atoms. Alkanes.
• Steam cracking

  Long chain hydrocarbons are heated into a gas. The gas is mixed with steam and heated to split into smaller molecules.
• Carbon

  4 available bonding electrons.

  Usually bonds with O, N, H.

  Can form long chains.
• In general the number of carbons differentiates alkanes
• Naming organic compounds

  End in ane/ene

  1= meth

  2= eth

  3= prop

  4= but

  5= pent

  6= hex

  7= hept

  8= oct

  9= non

  10= dec
• Branched alkanes/alkenes

  Branch- ends in yl

  e.g. Methyl propane/propene
• Boiling and melting points of alkanes

  Increase with the number of carbons.

  Usually low
• Solubility of alkanes

  Insoluble in water.

  Soluble in non-polar solvents.
• Reactivity of alkanes

  Generally unreactive.

  Reactions: combustion, halogenation
• Halogenation


  Alkanes react with halogens under UV light to produce halogenoalkanes
• Alkenes reactions


  Addition, hydration, combustion, polymerisation
• Addition of hydrogen to alkenes


  Unsaturated to saturated