chemistry 5.1

• ions are atoms that have gained or lost electrons, and are therefore charged.
• what are ions?

  atoms that gain or lose electrons
• transfer of electrons

  +opposite charges, attracted to each other by electrostatic connection
• ionic bonding involves a metal atom transferring one or more electrons to a non mental atom which from oppositely charged ions, therefore are attracted to each other by electrostatic forces forming an ionic bond
• the properties of ionic bonding is that they have high melting and boiling points. can conduct electricity when molten or dissolved in water
• what are the properties of ionic compounds

  • high melting and boiling points due to the strong electrostatic attraction between oppositely charged ions
  • in a solid state ionic compounds do not conduct electricity as ions are fixed in place
  • when molten- ions can move freely allowing to conduct electricity(also when dissolved in water)
• the two types of covalent structures are simple molecular substances and giant covalent structures
• the three types of giant covalent structures are diamond, graphite, silicon dioxide
• covalent bonds are very strong so will need lots of energy to break them apart
• when atoms share an pair of electrons, they form a covalent bond. these bonds between atoms are stong
• properties of simple covalent bonds

  • gases or liquids with low melting and boiling points
  • weak intermolecular forces between molecules
  • intermolecular forces increase with size( larger molecules have higher melting and boiling points)
  • don't conduct electricity- no overall charge
• properties of giant covalent bonds

  • are soilds with high melting points
  • linked to another atoms by strong covalent bonds
• an allotrope is a different form of the same element with the same chemical properties but different physical properties
• diamond each carbon bonded to 4 others and does not conduct electricity and is used in drill bits, glass cutting, gemstones
• graphite each carbon has bonded to 3 others conducts electricity because of delocalised electrons and is used in pencils and lubricants, layers can slide over each other
• why is important graphene

  • used in electronics and composites
  • single layer of graphite
• fullerenes can be used as lubricants, catalysts, and drug delivery systems
• nanotubes can be used for reinforcing materials such as a tennis racket
• properties of nanoparticles

  • diameter of 1nm-100nm
  • large surface area to volume ratio
  • used in medicine ( delivers drugs to inside cells)
• nano particles uses

  • kills bacteria (wounds , dressings, deodorants)
  • used in sun creams block harmful ultra violet
  • self cleaning windows
• nano-particles risks

  • so small could enter bloodstream
  • new material (long term effects isn't known)
  • could enter and damage environment
• the types of smart materials are included; shape memory alloys and shape memory polymers, thermochromic materials, photochromic pigments, polymer gels
• shape memory alloys and shape memory polymers

  • can be bent and deformed but return to original shape when heated
  • shape memory polymers include sports equipment ( gum shields, medical stitches)
  • car bodies, plates for bone fractures
• thermochromic materials

  • change colour when reacted certain temperature
  • used in mugs and spoons change when hot
• photochromic pigments

  • change colour when exposed to light
  • sunglasses that darken when in bright sun
• polymer gels

  • hydrogels absorbs 1,000 times their volume in water
  • used in nappies