Question | Answer |
Name the three types of Intermolecular Forces: | van der Waals Forces, Dipole-Dipole forces and Hydrogen Bonding. |
van der Waals forces: | Acts between ALL types of atoms and Molecules, is the weakest form of Intermolecular Force. Electron distribution can be uneven at any time, leading to slight dipoles, meaning slight attraction. |
Dipole-Dipole Forces: | Acts only between certain types of Molecules, is the second strongest type. Occurs between Polar molecules, the (delta) negative pole is attracted to the (delta) positive pole and this causes the molecules to align to each other. |
Hydrogen Bonding: | Only occurs when H is bonded to N, O or F, is the strongest type. Occurs when the Positive Hydrogen pole is attracted to a lone pair of electrons in molecules, causing a weak electrostatic force. |
Properties of Ice (2 answers): | Less dense than Liquid Water, resembles Diamonds structure. |
Boiling Points of HCL, H20 and NH4 are...: | Higher than expected because N, O and F are the only elements electronegative enough to have hydrogen bonding. |
Structures in which Hydrogen Bonding is important: | DNA (Double Helix held together by Hydrogen Bonds), Proteins Between then O-H and the N-H, |
Change in Enthalpy of Fusion | Is the amount of heat (energy) required to cause a Solid to change into a Liquid. |
Enthalpy | Heat Content - The amount of heat measured under constant pressure. |
Name the four types of Crystals: | Ionic Crystals, Metallic Crystals, Molecular Crystals and Macromolecular Crystals (covalent crystals). |
The 6 Crystal structures you need to know are: | Sodium Chloride (Ionic), Magnesium (Metalic), Diamond (Macro), Graphite (Macro), Iodine (Molecular) and Ice (Molecular). |
Give the structural features and properties of Diamond: | Each Carbon atom covalently bonds to 4 other carbons etc. In a tetrahedral shape they bond, creating a 3D lattice. Makes it very hard, very high melting point and doesn't conduct electricity. |
Give the structeral features of Graphite: | Each carbon bonds covalently to 3 other carbons, creating a 2D Hexagonal shape. Trigonal Planar bonding between the Carbons. Delocalised electrons create van der waals forces. It is soft/flakey, Conducts electricity and very high MP (breaks before metls) |
In increasing strength, list the types of electron repulsion in bonding: | Bonded Pair - Bonded Pair, Bonded Pair - Lone pair, Lone pair - lone pair. |
State the two principles of the Electron repulsion Theory: | Each pair of electrons in a molecule will repel all other electrons in the molecule, therefore, the electrons will position themselves as far from each other as possible. |
Shapes of Molecules, two pairs of electrons: | Linear molecules. 180 degrees. |
Shapes of molecules three pairs of electrons: | Trigonal planar. 120 degrees. |
Shapes of Molecules, four pairs of electrons: | Tetrahedral. 109.5 degrees. |
Shapes of Molecules, Five pairs of electrons: | Trigonal Bipyramidal. 120 degrees. |
Shapes of molecules, six pairs of electrons: | Octahedral. 90 Degrees. |
Electron Pairs exist as CHARGE CLOUDS. | Electron Pairs exist as Charge Clouds. |
VSEPR: | Valence Shell Electron Pair Repulsion. |