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Sunday, 17 November 2013

Topic 4.5: Physical Properties

4.5.1 Compare and explain the properties of substances resulting from different types of bonding.

Melting and boiling points

Melting and boiling points increases with increasing molecular size and the extent of polarity within the bonds of molecules.



Solubility

Consider an ionic compound being placed in water. At the contact surface, partial charges in the water molecules are attracted to ions of opposite charge in the lattice which may cause them to dislodge from their position. Ions separated from the lattice, which may cause them to dislodge from their positions. This is called hydrated.


It works the same for non-polar substances as well. Except it is covalent bonds which are dissolved instead of ionic bonds.


Anything that doesn't dissolve in water can dissolve in non-polar solvents, like lipids or hexane.


Electrical conductivity

Ability to conduct electricity depends on whether it contains electrons that are able to move. Ionic compounds are not able to conduct electricity in the solid state as the ions are firmly held within the lattice and can't move. Ionic compounds in aqueous or liquid state will be able to conduct electricity as there are free electrons.


This is a simple test to test whether it is a covalent or ionic compound. If the light doesn't light up, its a covalent bond.


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