Physical Pharmacy Lecture 4: States of Matter-2

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Questions and Answers

What is the result of three successive processes in crystallization from solution?

Supercooling, crystallization, and melting.

Supersaturation, formation of crystal nuclei, and crystal growth. (correct)

Formation of crystal nuclei, crystal growth, and supersaturation of the solution.

Crystal growth, crystallization, and supersaturation.

What is a characteristic of crystalline solids?

They have only atoms or molecules, but not ions.

They have a disordered molecular structure.

They have a mixture of ordered and disordered arrays of atoms or molecules.

They have highly ordered arrays of atoms or molecules. (correct)

What must happen in order to prepare a material in the amorphous state?

The material must be solidified slowly.

The material must be heated to a high temperature.

The material must be mixed with another substance.

The material must be solidified quickly. (correct)

What is a characteristic of crystalline solids when they melt?

They melt sharply at a specific temperature. Signup and view all the answers

What is a unit cell in a crystal?

A repeating unit in the crystal lattice. Signup and view all the answers

What can happen to crystalline material when mechanical or thermal energy is supplied?

It becomes amorphous. Signup and view all the answers

What are the units that constitute the crystal structure?

Atoms, molecules, or ions. Signup and view all the answers

What is the difference between crystalline and amorphous solids?

Crystalline solids have a regular structure, while amorphous solids have a disordered structure. Signup and view all the answers

What is the primary factor governing the physical state of a substance?

Intermolecular attraction forces Signup and view all the answers

What is the purpose of the Real Gas Law?

To correct for ideal gas law assumptions Signup and view all the answers

What type of bonding increases the attraction between molecules in liquids?

Hydrogen bonding Signup and view all the answers

What is the term for different types of solids that have the same chemical composition but differ in their crystalline structure?

Polymorphism Signup and view all the answers

What is the result of weak intermolecular forces in liquids?

Some ordering or regular arrangement among molecules Signup and view all the answers

What is the term for solids that have a regular, three-dimensional arrangement of molecules?

Crystalline solids Signup and view all the answers

What is the purpose of understanding polymorphism in pharmaceuticals?

To understand the pharmaceutical implications of polymorphism Signup and view all the answers

What is the term for a phase that is intermediate between the solid and liquid states?

Mesophases Signup and view all the answers

What is the main characteristic that distinguishes ionic crystals from molecular crystals?

Hardness and brittleness Signup and view all the answers

What type of bonds hold together metallic crystals?

Metallic bonds Signup and view all the answers

What is the term for the temperature at which a liquid passes into the solid state?

Melting point Signup and view all the answers

What does the heat of fusion of ice being approximately 79.7 calories per gram mean?

It requires a lot of energy to change the state of ice to water Signup and view all the answers

What is the trend observed in the melting points of normal saturated hydrocarbons (alkanes)?

They increase with increasing molecular weight Signup and view all the answers

Why do alkanes with an even number of carbon atoms have higher melting points than those with an odd number of carbon atoms?

Because the molecules are packed more efficiently in the crystal Signup and view all the answers

What is the main difference between ionic crystals and molecular crystals in terms of their physical properties?

Ionic crystals are hard and have high melting points, while molecular crystals are soft and have low melting points Signup and view all the answers

What is the characteristic of metallic crystals that allows them to be good conductors of heat and electricity?

The presence of a 'sea' of electrons Signup and view all the answers

What is a characteristic of amorphous materials compared to crystalline solids?

Glass transition temperature (Tg) Signup and view all the answers

What is observed in the XRD pattern of crystalline solids?

Sharp diffraction peaks Signup and view all the answers

What is the difference in stability between crystalline and amorphous materials?

Crystalline materials are more stable Signup and view all the answers

What happens to amorphous materials as the temperature increases above Tg?

They become more rubbery Signup and view all the answers

What is the purpose of X-ray diffractometry (XRD)?

To analyse the structure of solid materials Signup and view all the answers

What is the difference in solubility between crystalline and amorphous solids?

Amorphous solids are more soluble Signup and view all the answers

What is the glass transition temperature (Tg) associated with?

A change in the properties of the material Signup and view all the answers

What is the characteristic of amorphous materials below Tg?

They are brittle Signup and view all the answers

What is the characteristic of the amorphous form of a drug?

Higher solubility than crystalline form Signup and view all the answers

What is the effect of polymorphism on a drug?

It affects therapeutic activity Signup and view all the answers

What is an example of a crystalline solid subclass?

Polymorph Signup and view all the answers

What is the definition of polymorphism?

Ability of solid materials to exist in two or more crystalline forms Signup and view all the answers

What is a characteristic of polymorphs of the same drug?

They are chemically identical Signup and view all the answers

What is the tendency of metastable polymorphs?

To transform into the most stable polymorph over time Signup and view all the answers

What is a difference between different polymorphs of the same drug?

They have different melting points, XRD patterns, and solubility Signup and view all the answers

What percentage of APIs are estimated to have more than one polymorphic form?

More than 50% Signup and view all the answers

Study Notes

States of Matter

Phase transitions: change from one state of matter to another
Phase diagram: a graph that shows the relationship between temperature and pressure of a substance
Intermolecular forces: forces that govern the physical state of a substance

Real Gas Law

Corrects for ideal gas law assumptions about molecular interactions
Equation: (P - a/V^2)(V + nb) = nRT

Liquid State

Intermolecular forces of attraction in liquids (Van der Waals forces) impose some ordering or regular arrangement among molecules
Hydrogen bonding increases attraction in liquids and affects their physicochemical behavior

Solid State

Crystalline state: has regular structure that extends throughout the crystal
Amorphous solids have disordered molecular structure
Crystallization process: supersaturation, formation of crystal nuclei, and crystal growth

Crystalline Solids

Crystals contain highly ordered arrays of atoms or molecules held together by certain interactions
Unit cells: repeating units that constitute the crystal structure
All unit cells in a specific crystal have the same shape and size, containing the same number of molecules or ions arranged in the same way

Types of Crystals

Ionic crystals (e.g. NaCl): held together by ionic bonds
Atomic crystals (e.g. C, Diamond): held together by covalent bonds
Molecular crystals (e.g. CO2): held together by Van der Waal's forces
Metallic crystals: lattice point occupied by metal atoms, positively charged ions in a field of freely moving electrons

Melting Point and Heat of Fusion

Melting point: temperature at which a liquid passes into the solid state
Heat of fusion: amount of heat energy required to change a unit mass of ice at its melting point into water at the same temperature
Factors affecting melting point: molecular weight, van der Waals forces, and crystal structure

Amorphous Solids

Do not have definite melting points, but have a glass transition temperature (Tg)
Below Tg, the material is brittle and glassy; above Tg, the material is rubbery
Amorphous solids can be converted from crystalline materials by mechanical or thermal energy

Solid-State Characterization

X-ray diffractometry (XRD): a technique used to analyze the structure of solid materials
XRD pattern: distinguishing feature between crystalline and amorphous solids

Pharmaceutical Difference between Crystalline and Amorphous Solids

Stability vs therapeutic activity: crystalline materials have lower free energy and are more stable, while amorphous materials have higher free energy and are less stable
Amorphous forms of drugs often have higher solubility and bioavailability than crystalline forms

Crystalline Solids Sub-classes

Polymorphism: ability of solid materials to exist in two or more crystalline forms with different arrangements or conformations of the constituents in the crystal lattice
Multicomponent crystals: hydrates, solvates, and cocrystals, which consist of more than one type of molecule

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Description

Learn about states of matter, vapor pressure, boiling point, solid state crystallinity, solvates, and polymorphism in pharmacy. Lecture 4 of Physical Pharmacy course.