Paper 1

• Covalent bonds are formed by the sharing of electrons between atoms.
• what atoms does covalent bonding at

  Non-metal
• the number of shared pairs needed is equal to the group number on the periodic table
• An example of a giant covalent 


  A diamond
• Properties of a giant covalent bond

  High melting point

  requires lots of energy

  solid at room temperature
• Why does a giant covalent have a high melting and boiling point

  As the strong covalent bonds between the atoms must be broken to melt or boil the substance
• Examples of small molecules 


  Water
• Properties of small molecules

  Low melting and boiling point

  doesn't require a lot of energy

  normally gaseous or liquid at room temp
• Why do small molecules have low boiling and melting points

  as only the intermolecular forces need to be overcome to melt or boil the substance not the bonds between the atoms
• What is a single bond

  Each atom shares one pair of electrons
• What is a double bond 


  Each atom shares two pairs of electrons
• How are large molecules joined

  Many repeated units joined by covalent bonds to form a Chain
• how are separate large molecule chains held together

  The separate chains are held together by intermolecular forces that are stronger in small molecules
• Properties of large molecules

  Melting and boiling points are inbetween giant covalents and small molecules
• what other properties do large molecules have

  Have stronger intermolecular forces

  these require more energy to overcome

  normally solid at room temp
• Graphite structure and what it is made out off

  Made only of carbon each atom bonds to 3 different carbon atoms

  forms hexagonal rings in layers

  each atom has a spare electron

  this electron gets delocalised and is free to move around the structure

  
• The hardiness of graphite

  The layers can slide over each other as they are not covalently bonded

  graphite is softer than diamonds
• What is different between a diamond and graphite carbon structure

  carbon atoms in a diamond has four strong covalent bonds

  carbon atoms in graphite had three strong covalent bonds
• What is the conductivity of graphite

  The delocalised atom which is free to move can carry charges and allows an electrical current to flow.

  graphite is a conductor of electricity
• fullerenes properties

  Hollow cages of carbon atoms bonded together in one molecule

  can be arranged as a sphere or tube

  held together by a weak intermolecular force so can slide

  conducts electricity
• Fullerenes spheres

  Buckminsterfullerenes was the first one to be discovered

  this has 60 carbon atoms
• What can fullerenes be used for

  The sphere fullerenes can be used as lubricants and in drug delivery
• Nanotube fullerenes 


  The carbon atoms are arranged in cylindrical tubes
• What do their high tensile help with

  Makes them difficult to break when pulled

  makes them useful in electronics
• Most covalent structure don’t conduct electricity. Which ones do conduct?

  Graphite

  graphene

  fullerenes
• what are the 2 types of energy transfer

  Endothermic and exothermic
• Which way does exothermic reaction go

  to the surroundings
• Which way does endothermic go


  from the surroundings
• What is the key thing about energy

  It cannot be made or destroyed. So in a chemical reaction the amount of energy stays the same
• What is a reaction profile

  It shows whether a reaction is exothermic or endothermic
• Which reaction is this

  Exothermic reaction

  
• Which reaction is this

  endothermic reaction

  
• Where does the temperature change in exothermic reaction

  Temperature of the surroundings increase
• What are examples of exothermic reactions

  Oxidation, combustion, neutralisation
• What are every day uses of exothermic energy

  Self heating cans, hand warmers
• What happens at the bonds of exothermic reaction

  More energy released when making bond than required to break bonds
• Where dose the temperature change in endothermic reaction

  Temperature of the surroundings decrease
• what are examples of endothermic reactions 


  Thermal decomposition, citric acid and sodium hydrogen carbonate
• What are every day uses of endothermic reactions

  Sports injury packs
• What happens the bond in an endothermic reaction

  Less energy released when making bonds than to break bonds