Structure 2.4 Flashcards
Alloy properties
Lower melting points, less malleable/ductile, harder, less directional bonding
Alloys
A mixture of more than one metal
Polymer
A repeating chain of monomers held together by covalent bonds
Monomer
Individual repeating units in a polymer
Monomers joint in addition reactions
Addition polymer and condensation reactions - don’t form by products
Thermoplastics
Soften when heated and harden when cooled, recyclable
Thermosetting plastics
Change irreversibly into hardened thermosets and cannot be recycled
Elastomers
Polymers that are flexible and can be reformed under a force but will return to the original shape when stress is released
Bonding triangle
Shows the three extreme types of bonding plotted against the difference in electronegativity and the change in electronegativity
Ionic bond
Electrostatic attractions between two oppositely charged ions
Covalent bond
The electrostatic attraction between the nuclei of two atoms and their valence electrons, sharing of electrons
Metallic bonds
The electrostatic attraction between the cations and sea of delocalised valence electrons
When does a solid melt?
When attractive forces between particles are overcome and particles are free to move
What is melting point influenced by?
The way in which particles pack in the solid state
Ionic compounds conductivity
Don’t conduct in solid state but conduct when molten or in aqueous liquid
Why do ionic compounds (molten/in aqeous) decompose when conducting?
As conductivity is due to movement of electrons
Conductivity of allotropes of non metals
Usually good as they have delocalised electrons
Elasticity
The ability of a material to resist a distorting influence and return to original when force is removed