Types of substances

• What structure do ionic compounds have?

  Regular lattice (giant ionic lattices), the are strong electrostatic forces in all directions between oppositely charged ions
• Why do ionic compounds have a high melting point? 


  They​ ​have​ ​​high​ ​melting​ ​and​ ​boiling​ ​points​,​ ​because​ ​a​ ​lot​ ​of​ ​energy​ ​is​ ​required​ ​tobreak​ ​the​ ​many​ ​strong​ ​bonds.
• When can't ionic compounds conduct electricity when solid?

  Ions are fixed and unable to move and carry charge with them.
• Why can ionic compounds conduct electricity when molten or dissolved in water?

  Ions are free to move around and can carry current
• Why do simple molecular structures have low boiling or melting points?

  Substances​ ​that​ ​consist​ ​of​ ​small​ ​molecules​ ​have​ ​weak​ ​intermolecular​ ​forcesbetween​ ​the​ ​molecules.​ ​These​ ​are​ ​broken​ ​in​ ​boiling​ ​or​ ​melting,​ ​​not​ ​the​ ​covalent bonds.
• The​ ​intermolecular​ ​forces​ ​increase​ ​with​ ​the​ ​size​ ​of​ ​the​ ​molecules,​ ​so larger​ ​molecules​ ​have​ ​higher​ ​melting​ ​and​ ​boiling​ ​points.
• Why do substances consisting of small molecules not conduct electricity?

  Small​ ​molecules​ ​do​ ​not​ ​have​ ​an​ ​overall​ ​electric​ ​charge​ ​but ​some breakdown​ ​in​ ​water​ ​to​ ​form​ ​ions​ ​which​ ​can​ ​conduct​ ​electricity
• Are simple molecular compounds soluable in water?

  Many are insoluable, but are soluable as they can form intermolecular forces with water that are stronger than those between water and those between themselves
• Examples of simple molecular compounds


  Water, methane, ammonia
• Why do giant covalent structures have very high melting points?

  Atoms in the structure are linked to other atoms by strong covalent bonds which require lots of energy to break.
• Can giant covalent structures conduct electricity?

  Some can
• What state are simple molecular forces at room temp?

  Gaseous
• As you go down group 7 the atoms (and thus molecules) get bigger. This means there will be more intermolecular forces, and so more energy (and a higher temperature) will be required to break them.  
• Why don't giant molecular structures have weak intermolecular forces?

  there is only one structure
• Graphite and diamond are different forms of carbon
• Graphite and diamond are forms of giant covalent substances
• What is an allotrope?

  Different structural forms of the same element in the same physical state.
• How many carbon atoms are bonded to eachother in a diamond?

  Each carbon atom is covalently bonded to 4 other carbon atoms
• What is the maximum number of carbon atoms a carbon atom can bond with?

  4
• Why is diamond strong and why does it have a high melting point?

  In the regular 3D lattice, the covalent bonds between the carbon atoms are very strong.
• Why doesn't diamond conduct electricity?

  It has no free ions or electrons that can move around.
• Why is graphite able to conduct electricity and heat?

  it is able to bond with up to 4 carbon atoms but only bonds with 3 leaving a spare electron which becomes delocalised and can move freely, and so is able to carry charge.
• Why is graphite softer than diamond?

  The 2D layers in graphite are stacked on top of eachother with weak intermolecular forces so layers are able to move over eachother making it softer and easier to break.
• Why is graphite used to make electrodes?

  Graphite has one delocalised electron and can therefore conduct electricity unlike unlike diamond.
• Why is graphite used to make lubricants?

  It has weak intermolecular forces and no covalent bonds so layers can slide over eachother, and therefore is soft and slipper
• Why is diamond used for cutting tools?

  Rigid structure makes it very hard
• What are the properties of graphene?

  It is a single layer of graphite with strong covalent bonds.
• What do the properties of graphene make it useful in?

  Electronics and composites
• Carbon​ ​can​ ​also​ ​form​ ​fullerenes​ ​with​ ​different​ ​numbers​ ​of​ ​carbon​ ​atoms.
• The ​​first ​​fullerene ​​to ​​be​​ discovered​​ was​​ Buckminsterfullerene​​(C6​0)​,​​which has​ ​a​ ​spherical​ ​shape
• The sheets can be folded into two types of 3D structure: tubes and spheres, which are known as fullerenes.
• What are nanotubes made from?

  Fullerenes
• Why are nanotubes useful in electronics?

  This is because each carbon atom has one delocalised electronwhich can carry charge.
• How is fullerene used in medicine?

  Scientists form spheres which act as cages that carry around molecules, like drugs, to deliver it to parts of the body.
• Fullerene is used as an industrial catalyst in chemical reactions.
• What is a nanotube?

  Cylindrical fullerene with very high length to diameter ratio.
• What are carbon nanotubes used for?

  Their properties make them useful for nanotechnology, electronics and materials.
• Which feature of carbon nanotubes makes them useful in tennis racket frames?

  High strength to weight ratio, This means that they can make the tennis racket frame a lot stronger without making them much heavier.
• simple polymers consist of large molecules containing chains of carbon atoms
• What do polymers have?

  Large molecules.