Chemistry Unit 1.4 - Substances and their Structure and Properties

Notes on Substances and their Structure and Properties

HideShow resource information
  • Created by: mar-rii
  • Created on: 01-01-10 16:55
Preview of Chemistry Unit 1.4 - Substances and their Structure and Properties

First 592 words of the document:

Chemistry Unit 1.4: Substances and their Structure and Properties
CARBON
Diamond
Structure - Each carbon atom is covalently bonded to another 4 carbon atoms which forms up a tetrahedral
shape which repeats itself throughout the macromolecule.
Melting point - The Melting point of diamond is 3820 degrees Kelvin which is extremely high and this is
because of the multiple strong covalent bonds throughout the molecule.
Density - The density of diamond is 3.52g/cm3
Electrical conductivity - Diamond does not conduct electricity.
Graphite
Structure - Each carbon atom is covalently bonded to another 3 carbon atoms which forms up different
planes which are joined by weak intermolecular forces. There is a "sea" of delocalised electrons between the
layers.
Melting point - The Melting point of graphite is 3652 degrees Kelvin which is extremely high and this is
because of the multiple strong covalent bonds throughout the molecule.
Density - The density of graphite is 2.09g/cm3
Electrical conductivity - Graphite is a very good electrical conductor because of the sea of delocalised
electrons.
ICE
Structure - Each Ice molecule forms up a regular hexagonal lattice out of water molecules which bond to each
other through hydrogen bonding between a hydrogen and a lone pair of electrons on a oxygen. Ice can form
up 9 other structural forms at different temperatures and pressures. At normal pressures it can also form up
a structure similar to diamond.
Melting point - The Melting point of Ice is 273 degrees Kelvin which is low because the hydrogen bonds are
weak.
Density - The density of Ice is 0.93g/cm3 which is less than water's 1.00g/cm3. This means ice floats.
Electrical conductivity - Ice does not conduct electricity.
SODIUM CHLORIDE
Structure - Sodium chloride forms crystals with cubic symmetry. In these, the larger chloride ions, shown to
the left as yellow spheres, are arranged in a cubic close-packing, while the smaller sodium ions, shown to the
left as blue spheres, fill the octahedral gaps between them. Each ion is surrounded by six of the other kind.
This same basic structure is known as the halite structure. It is held together with an ionic bond and
electrostatic forces.
Melting point - The Melting point of NaCl is 1074 degrees Kelvin due to the strong electrostatic forces.
Density - The density of graphite is 2.16g/cm3
Electrical conductivity - Sodium chloride only conducts electricity in the molten or aqueous state where the
ions are free to move.
IODINE
Structure - Each Iodine atom bonds covalently to another to form a I2 molecule. These I2 molecules then
bond to each other through weak inter-molecular bonds. In solid iodine the molecules are arranged in waves
as shown right.
Melting point - The Melting point of Iodine is 386 degrees Kelvin.
Density - The density of Iodine is 4.94 g/cm3.
Electrical conductivity - Iodine does not conduct electricity.
POLYTHENE
Structure - Polythene is a giant covalent structure formed from polymerisation of ethene. This forms up very
long chains which then lay down into two regions, amorphous regions (A) and crystalline regions (B) The
amount of each type of region varies and causes different properties.
Melting point - The Melting point of polythene is ~388-408 degrees Kelvin.
Density - The density of Polythene is 0.91-0.97g/cm3.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Electrical conductivity - Polythene does not conduct electricity.…read more

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »