1.5 Types of Substance
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Ionic compound properties
-High melting/boiling point -Can’t conduct electricity when solid -Can conduct electricity when molten, aqueous, liquid or gas -Soluble in water
Why do ionic compounds have high boiling points
The strong ionic bonds due to strong electrostatic forces of attraction takes lots of energy to overcome
Why can’t ionic compounds conduct electricity when solid
The ions aren’t free to move so can’t carry charge
Why can ionic compounds conduct electricity when molten, liquid or gas
The ions are free to move so can carry charge
Why can ionic compounds conduct electricity when dissolved in a solution
The ions separate in the solution and are free to move and carry charge
Different types of representation for atomic structure
-Molecular formula -2D representations -Dot and cross diagrams -Space-filling -Ball and stick models
Simple molecular substance properties
-Low melting/boiling point -Larger molecules have higher melting/boiling points -Can’t conduct electricity -Usually insoluble in water
Why do simple molecular substances have low melting/boiling points
The weak intermolecular forces of attraction between molecules does not require a lot of energy to break
Why does the melting/boiling point of simple molecular substances increase with size
As the molecule gets bigger the strength of the intermolecular forces increases so more energy is needed to break them
Why can’t simple molecular substances conduct electricity
They have no free electrons to carry charge
What are the bonds in giant covalent structures
Covalent bonds
Giant covalent structures general properties
-Very high melting and boiling points -Can’t conduct electricity (except graphite/graphene) -Insoluble in water
Carbon based covalent structure examples
-Diamond -Graphite/graphine -Fullerines (nanotubes, buckminsterfullerene)
Diamond properties
-High melting point -Really hard -Can’t conduct electricity
Diamond arrangement
Each atom covalently bonded to four others
Why does diamond have a high melting point
It’s strong covalent bonds need a lot of energy to break
Why is diamond hard
The strong covalent bonds hold it in a rigid lattice structure
What is diamond used for
Strengthening cutting tools (saw teeth and drill bits)
Why is diamond used to strengthen cutting tools
It is really hard
Why can’t diamond conduct electricity
It has no free electrons or ions
Graphite properties
-Soft and slippery -High melting point -Can conduct electricity
Graphite arrangement
Each atom covalently bonded to three others creating sheets of hexagons
Why is graphite soft and slippery
There aren’t any covalent bonds between the layers so they’re only held together weakly
Use of graphite
Lubrication, electrodes