1 + 2 States of Matter Flashcards
(21 cards)
What are intermolecular Forces + why are they important?
Forces existing between molecules. Important to achieve effective and stable formulations that act in a reproducible manner in the body.
What are repulsive forces?
Forces existing due to like charges of electrons within electron clouds repelling.
Forces increase exponentially with decreasing molecular distance.
List 4 types of attractive forces and what they are
- ion-dipole: between ions and polar molecules
- dipole-dipole: between polar molecules (vdW)
- london dispersion: between all molecules (vdW)
- Hydrogen bonds: between H and O, N, F
Describe properties and behaviours of molecules in gaseous state
Molecules move vigourously and randomly to fill volumes. Temperature affects speed of molecules and pressure results from molecular collisions within a contained space.
What is liquefaction of gas and how does this occur?
The formation of liquid from gas phase.
- Kinetic energy is removed as temperature decreases.
- molecules come closer together as pressure increases.
When attractive forces predominate, gases condense to liquids.
What is critical temperature?
A teemperature at which above this, the liquid state no longer exists.
What is critical pressure
pressure required to liquefy gas at a critical temperature.
describe crystalline solids
- have defined shape and symmetry
- have a defined, sharp melting point
- latent heat of fusion is fixed
- anisotropic, having different properties in different directions
describe amorphous solids
- do not have form (geometry)
- melts over a range of temperatures
- latent heat of fusion is not definite
- isotropic (same properties along axis)
What is the latent heat of fusion
total energy absorbed when 1 mol of solid melts, or is liberated when 1 mol of solid freezes
What is a crystal habit? give examples.
The habit of a crystal describe what overall shape it takes; e.g. acicular, prismatic, pyramidal, tabular etc.
What is polymorphism in terms of solids
The existance of elements/molecules in one or more crystalline forms
What are liquid crystals?
Systems where there are some degree of molecular order while maintaining an overall fluid state.
What is birefringence and when does this occur?
Optical birefringence is the refraction of light in multiple directions. This occurs in crystalline solids that have differing concentrations along different axes.
What is the triple point of a phase diagram?
Triple point is a point where all 3 phases exist (solid, liquid, gas).
At pressures lower than where the triple point is, liquid will not exist.
What is supercritical matter
This is the state generated when a gas is held under a temperature and pressure above the critical point. This exists in the supercritical region.
Describe properties of supercritical matter
properties are between gas and liquid; known as a mesophase - supercritical fluid
- permeates solid substances
- low viscosity
- high diffusivity
- increased densities
What is an example of supercritical matter and how is it used
supercritical carbon dioxide is used for extractions i.e. decaffinating tea and coffee or nicotine from tobacco.
It is also used as a reaction medium for drug synthesis
What is the phase rule and what does it show?
Finds the degrees of freedom - the number or independent variables that must be known to define a system.
F = C - P + 2
Describe two component systems involving liquid phase(s) (examples)
Max degrees of freedom = 3
- In a single liquid phase, water and phenol are miscible
- In a two liquid phase, water and phenol are immiscible.
What is the eutectic point in a solid-liquid two component system?
the point at which it is the lowest temperature that liquid phases can exist. At this point there are no degrees of freedom.
