Chapter 11 Flashcards
What differentiates the phases of matter?
Density, Shape, Volume, Inter-molecular Forces
Gas
Low Density, Shape of Container, Volume of Container, Weak Inter-molecular Forces
Liquid
Medium Density, Shape of Container, Fixed Volume, Medium Inter-molecular Forces
Solid
High Density, Fixed Shape and Volume, Strong Inter-molecular Forces
How to force a change from Gas to Liquid
Increase pressure, lower temperature
How to force a change from liquid to solid
Lower temperature
How to force a change from Gas to Solid
Lower temperature
What is the weakest inter-molecular force?
London Dispersion Force
London Dispersion Forces
As electron move around in their orbitals in an atom, at any given moment more of them may be on one side of the atom than the other. It results in the atom having a dipole moment which induces a dipole in the next atom over creating a weak attraction between the atoms
Where do Dispersion Forces exist?
Every Chemical System
What factors determine how big the dispersion force is?
Molar Mass
Molecular Shape
Size
How does Molar Mass affect Dispersion Forces?
Heavier molecules have more dispersion interactions
How does molecular shape affect Dispersion Forces?
Longer, straighter molecules ten to have more dispersion interactions than globular ones
How does Size affect Dispersion Forces?
Atoms that have lower electronegativities and ionization energies are easier to polarize and have stronger dispersion forces
Dipole Force
Molecules line up so that the negative end of one is close to the positive end of another. Polar molecules have a higher melting and boiling point than non-polar molecules
Where do Dipole Forces exist?
All molecules that have a permanent dipole
Miscibility
Ability of liquids to mix without separating into two phases
What is needed to mix polar and non-polar molecules?
Emulsifier
When does Hydrogen Bonding occur?
Only in certain molecules that have extremely strong dipole-dipole interactions
How strong are hydrogen bonds?
Very strong
Why are hydrogen bonds so strong?
The very electronegative atoms cause the hydrogen bonded to them to have a large partial positive charge
Ion-Dipole Forces
Interaction between an ion and a polar compound
Responsible for ionic solids dissolving in water
Strongest inter-molecular force
Why do something float on water?
Liquids form ‘a skin’ along their surface, called surface tension
Surface Tension
Water molecules on the surface have a higher potential energy than those in the interior.
The liquid then tries to minimize the number of surface molecules, resisting changes that would increase its surface area
What does the rate of Vaporization depend on?
Temperature of the liquid
Surface area of the liquid
Volatility of the liquid (inter-molecular forces)
Critical Point
Point where the vapour and the liquid have the same density
What happens at Critical point?
Forms new phase: Supercritical fluid
Sublimation
Solid to Gas without going through the liquid phase
Deposition
Opposite of Sublimation
What do phase diagrams show?
Which phase is most stable under certain conditions
The conditions that favour each phase
