chemistry

chemistry

1. polymers

   • special properties of polymers
     • an artificial hip replaces the ball and socket of a worn hip joint. this socket is made of the polymer teflon
       • its surface hasalmost no friction, so the ball of titanium allows swivels freely
         • it is non toxic and inert (non-reactive), essential inside the body
           • it can withstand high temperatures (it is also used in non-stick pans)
     • the viscosity of slime depends on the concentrations of the solutions and the length of the polymer chains.
   • uses of polymers
     • packaging materials must be strong, light and flexible
       • water prrofing for tend fabrics must repel water
         • dental polymers for crowns and dentures are designed to harden when exposed to ultraviolet light
           • wound dressings must breath and hydrogels must retain moisture for rapid healing
   • disposing of polimers
     • reasons for recycling
       • most polymers are produced from non-renewable crude oil. they are not biodegradable. they take up space int he waste dumps and landfill sites.
         • polymers can be recycled. they are shredded, melted and formed into pellets used to make new objects such as fleeces
           • it is becoming cheaper to recycle polymers instead of throwing them away
     • alternatives to recycling
       • polymers can be burn to generate heat energy, however they can produce particle pollution and toxic fumes that damage the enviroment
       • to make them biodegradable, polymers are mixed with cellulose or starch that microorganisms will break down

2. alkenes

   • allkenes are a family of hydrocarbons
     • the smallest alkene is ethene, chemical formula C2H4. the next is propene, C3H6
       • the general formula for the alkenes is CnHn2n