1 + 2 States of Matter

Question 1

What are intermolecular Forces + why are they important?

Answer 1

Forces existing between molecules. Important to achieve effective and stable formulations that act in a reproducible manner in the body.

Question 2

What are repulsive forces?

Answer 2

Forces existing due to like charges of electrons within electron clouds repelling.
Forces increase exponentially with decreasing molecular distance.

Question 3

List 4 types of attractive forces and what they are

Answer 3

• 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

Question 4

Describe properties and behaviours of molecules in gaseous state

Answer 4

Molecules move vigourously and randomly to fill volumes. Temperature affects speed of molecules and pressure results from molecular collisions within a contained space.

Question 5

What is liquefaction of gas and how does this occur?

Answer 5

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.

Question 6

What is critical temperature?

Answer 6

A teemperature at which above this, the liquid state no longer exists.

Question 7

What is critical pressure

Answer 7

pressure required to liquefy gas at a critical temperature.

Question 8

describe crystalline solids

Answer 8

• have defined shape and symmetry
• have a defined, sharp melting point
• latent heat of fusion is fixed
• anisotropic, having different properties in different directions

Question 9

describe amorphous solids

Answer 9

• do not have form (geometry)
• melts over a range of temperatures
• latent heat of fusion is not definite
• isotropic (same properties along axis)

Question 10

What is the latent heat of fusion

Answer 10

total energy absorbed when 1 mol of solid melts, or is liberated when 1 mol of solid freezes

Question 11

What is a crystal habit? give examples.

Answer 11

The habit of a crystal describe what overall shape it takes; e.g. acicular, prismatic, pyramidal, tabular etc.

Question 12

What is polymorphism in terms of solids

Answer 12

The existance of elements/molecules in one or more crystalline forms

Question 13

What are liquid crystals?

Answer 13

Systems where there are some degree of molecular order while maintaining an overall fluid state.

Question 14

What is birefringence and when does this occur?

Answer 14

Optical birefringence is the refraction of light in multiple directions. This occurs in crystalline solids that have differing concentrations along different axes.

Question 15

What is the triple point of a phase diagram?

Answer 15

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.

Question 16

What is supercritical matter

Answer 16

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.

Question 17

Describe properties of supercritical matter

Answer 17

properties are between gas and liquid; known as a mesophase - supercritical fluid

• permeates solid substances
• low viscosity
• high diffusivity
• increased densities

Question 18

What is an example of supercritical matter and how is it used

Answer 18

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

Question 19

What is the phase rule and what does it show?

Answer 19

Finds the degrees of freedom - the number or independent variables that must be known to define a system.
F = C - P + 2

Question 20

Describe two component systems involving liquid phase(s) (examples)

Answer 20

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.

Question 21

What is the eutectic point in a solid-liquid two component system?

Answer 21

the point at which it is the lowest temperature that liquid phases can exist. At this point there are no degrees of freedom.