Intermolecular Forces, Liquids, Soldis And Materials Flashcards
Describe solids, liquids and gases
Solids: ordered, no diffusion, particles are close together and do not change position
Liquids: disorder, particles move and are close, slow diffusion
Gas: total disorder, lots of empty space, rapid diffusion
Condensation polymerization
Formation of polymers via eliminating small molecules like HCl or H2O
Is there a point where all phases (solid, liquid, and gas) can coexist at once?
Yes, the triple point occurs at a certain temperature and pressure
What is it called when semiconductors that are inorganic compounds have their 4 valence electrons increased or decreased?
Doping
When inorganic semiconductors have more than 4 valence electrons due to doping, what type of band is produced?
N-type (the extra electrons are added to the conduction band)
When inorganic semiconductors have less than 4 valence electrons due to doping, what type of band is produced?
P-type (holes in the valence band)
How are solar cells formed? And what type of energy are they converting?
By joining n-type and p-type silicon solar cells. They convert light/optical energy into electrical energy
What type of energy do LEDs convert?
LEDs do the opposite of solar cells and convert electrical energy into light/optical energy
Describe molecular solids and give an example of one
-low melting points and boiling points due to weak intermolecular forces
-units are molecules
-held together by intermolecular forces
-a type of crystalline solid
-ex: ice or sucrose
Describe molecular solids
-low melting points and boiling points due to weak intermolecular forces
-units are molecules
-a type of crystalline solid
Describe insulators and give some examples of them
-have a large band gap (the energy difference between a filled band and an empty band)
Examples: wood, air, rubber, glass and most plastics
Describe metallic solids
-consist of metal atoms held together by metallic bonding
-conduct electricity
-ex: gold (Au)
Describe ionic solids
-consist of positive and negative ions held together by ionic bonds
-have high melting points
-hard and brittle
-poor conductors of electricity due to the strength of ionic bonds
-ex: sodium chloride (NaCl)
Covalent-network solids
-high melting points and are much harder than molecular solids
-held together by strong covalent bonds
-ex: diamond (boiling point of 3550 degrees), quartz
Non bonding solids
-held together by London dispersion forces
-low melting point
-ex: xenon (Xe)
Describe semi conductors
-have a small band gap so heat or radiation can promote electrons from the valence band to the conduction band
-conductivity in inorganic semiconductors can be increased by doping
What is viscosity and how does molecular shape affect it?
-Viscosity is measured by a fluids resistance to flow (honey has higher viscosity than water)
-larger, more complex molecules have higher viscosities because they are more likely to interlock or entangle
What is it called when a solid turns into a liquid?
Melting
From liquid to solid
Freezing
Gas to liquid
Condensing
From liquid to gas
Boiling
Gas to solid
Sublimination
Solid to gas
Deposition
Is vapour pressure higher or lower when intermolecular forces are stronger
Lower
What happens at the triple and critical point?
At the triple point all three phases are in equilibrium and at the critical point a supercritical fluid is formed
When does boiling occur in relation to vapour pressure?
When vapour pressure=external pressure
Give some examples of Intramolecular forces, are they strong or weak?
-Covalent bonding, ionic bonding
-They are relatively strong
Give examples of intermolecular forces, are they strong or weak?
-relatively weak
-London dispersion forces
-Hydrogen bonding
-Dipole dipole
The stronger the intermolecular forces the lower/higher the boiling and melting points
Higher
How to identify if a compound has hydrogen bonding
If it contains an O-H, F-H or N-H bond
What is the strongest intermolecular force?
Hydrogen bonding
When do dipole-dipole interactions happen?
When the positive end of a polar molecule interacts with the negative end of another polar molecule. In order to be a polar molecule the molecule must have a net dipole.
Order the intermolecular forces in order from strongest to weakest
Hydrogen bonding > dipole dipole > London dispersion forces
When are London dispersion forces present in compounds?
They are present in all compounds regardless whether the molecule is polar or nonpolar
If a molecule is polar and has hydrogen bonding what does that mean?
It means that it has all three intermolecular forces due to the polarity
Explain the relationship between viscosity and intermolecular forces
Viscosity increases with the strength of intermolecular forces
Why does surface tension happen?
Because molecules at the surface are more attracted to each other than they are to the air
Cohesive forces
Attraction of molecules to each other (liquid molecules sticking to each other)
Adhesive forces
Attraction of molecules for surface (liquid molecules sticking to the surface)
Are the adhesive forces between the glass (capillary) and the liquid weaker or stronger than the cohesive forces between the molecules in the liquid?
The adhesive forces are weaker than the cohesive forces
Liquid crystals
Intermediate phases between solid and liquid, rod-shaped, polar molecules
Nematic phase of liquid crystals
Aligned in one direction
Smectic phase of liquid crystals
Aligned in one direction and in layers
Cholesteric phase of liquid crystals
Aligned in one direction and in twisted/rotated layers
Addition polymerization
Breaks down double bonds into all single bonds to form polymers from monomers
