Property Of Solids (Part 2) PDF

PROPERTY OF SOLIDS (PART 2) – DR. YANG 1. What is the Stokes-Einstein equation used for? A: It relates the diffusion coefficient of a particle to its size and the viscosity of the solvent. 2. What is the principle behind Differential Scanning Calorimetry (DSC)? A: It measures the difference in h...

PROPERTY OF SOLIDS (PART 2) – DR. YANG 1. What is the Stokes-Einstein equation used for? A: It relates the diffusion coefficient of a particle to its size and the viscosity of the solvent. 2. What is the principle behind Differential Scanning Calorimetry (DSC)? A: It measures the difference in heat required to raise the temperature of a sample and a reference as a function of temperature. 3. What is Thermogravimetric Analysis (TGA) used for? A: It determines material properties by measuring mass changes due to decomposition, oxidation, or moisture loss. 4. What does Thermomechanical Analysis (TMA) measure? A: Changes in the dimension or mechanical properties of a sample as a function of temperature. 5. What is melting point depression? A: It occurs when impurities lower the melting point of a compound, broadening the melting range. 6. What is eutectification? A: The process of forming a eutectic mixture, where the melting point of the mixture is lower than that of the individual components. 7. Define polymorphism in materials science. A: The ability of a solid material to exist in more than one form or crystal structure. 8. What are enantiotrophs? A: Polymorphs that are stable at different pressures and temperatures. 9. What are monotrophs? A: Polymorphs where only one form is stable below the melting point. 10. What factors affect polymorphism? A: Temperature, humidity, solvents, grinding, photostability, and excipients. 11. How does temperature affect polymorphism? A: Temperature can induce transitions between polymorphic forms, affecting stability. 12. What is the role of humidity in polymorphism? A: Humidity can affect the stability and transition of polymorphic forms. 13. What are the techniques used to study polymorphism? A: Optical crystallography, hot stage microscopy, X-ray diffraction, FTIR, and microcalorimetry. 14. What is the significance of the refractive index (RI)? A: It describes how light propagates through a material and is used in optical crystallography. 15. What is Fourier Transform Infrared Spectroscopy (FTIR) used for in polymorphism studies? A: To obtain the infrared spectrum of a sample, aiding in polymorph identification. 16. What is pseudopolymorphism? A: The phenomenon where solvent molecules are incorporated into the crystal lattice, forming solvates. 17. What is the effect of impurities on melting point? A: Impurities lower the melting point and broaden the melting range of a compound. 18. How is the eutectic point defined? A: It is the lowest temperature at which a mixture of two compounds melts. 19. What is the melting point depression test used for? A: To identify compounds by mixing an unknown sample with a known compound and observing the melting behavior. 20. How does DSC distinguish between sample and reference? A: It measures the heat flow difference as temperature increases. 21. What is the function of TGA in pharmaceutical analysis? A: It helps analyze moisture content, decomposition, and other mass changes in drug substances. 22. What is a eutectic mixture and give an example? A: A mixture with a lower melting point than its components, e.g., lidocaine and prilocaine. 23. What is the role of TMA in pharmaceutical analysis? A: It measures changes in dimensions of materials, such as expansion or contraction due to temperature. 24. What is a binary eutectic phase diagram? A: It represents the relationship between temperature and composition for two substances forming a eutectic mixture. 25. What is the significance of crystal habits in polymorphs? A: Different crystal habits can affect the formulation and stability of pharmaceuticals. 26. How can polymorphism affect drug formulation? A: Polymorph transitions can cause changes in bioavailability, solubility, and stability. 27. What is the difference between metastable and stable polymorphs? A: Metastable polymorphs can convert to more stable forms over time. 28. What is the impact of polymorphism on suspension formulations? A: Polymorphic changes can alter particle size, leading to caking or instability in suspensions. 29. How does the presence of excipients influence polymorphism? A: Excipients can stabilize or destabilize polymorphs, affecting drug formulation. 30. What is the use of X-ray diffraction in polymorphism? A: It identifies crystal structures by analyzing the diffraction patterns of X-rays through a sample. 31. What is thermodilatometry? A: A technique that measures dimensional changes in a sample with minimal force applied, under temperature variation. 32. Why is grinding a factor in polymorphism? A: Grinding can induce polymorphic transitions by altering the crystal structure. 33. What is the function of FTIR in detecting polymorphs? A: FTIR provides a rapid qualitative and quantitative analysis of polymorphs based on their infrared absorption spectra. 34. How does the method of preparation affect polymorphism? A: Different preparation methods can result in distinct polymorphic forms with varying properties. 35. What is the transition temperature in polymorphs? A: The temperature at which one polymorph converts into another. 36. What does the heat of fusion represent in thermal analysis? A: The energy required to convert a solid into a liquid at its melting point. 37. How can polymorphism cause issues in suppository formulation? A: Changes in the polymorphic form of the base, like theobroma oil, can result in altered melting characteristics. 38. What are the effects of photostability on polymorphs? A: Exposure to light can cause polymorphic transitions, affecting drug stability. 39. What is the relevance of solubility in polymorphism? A: Different polymorphs have varying solubilities, which can impact drug absorption and bioavailability. 40. How is optical crystallography used in polymorphism screening? A: It examines crystal structures and the stability of metastable forms under different conditions. 41. What is the significance of pseudopolymorphs in drug formulation? A: Pseudopolymorphs, which incorporate solvent molecules, can alter the solubility and stability of drugs. 42. How can temperature and pressure affect polymorphic stability? A: Enantiotropic polymorphs are stable over different ranges of temperature and pressure, while monotrophic polymorphs have only one stable form. 43. What does microcalorimetry measure in polymorphism studies? A: It detects small heat changes during transitions between polymorphs, helping to characterize thermal behavior. 44. What are the benefits of using DSC in polymorphism studies? A: It provides information about the heat transitions between polymorphs and helps determine the melting points. 45. What is the significance of excipient incompatibility in polymorph stability? A: Incompatible excipients can destabilize polymorphs, leading to formulation failures. 46. What are the common applications of polymorphism in the pharmaceutical field? A: Polymorphism is used to optimize drug solubility, stability, and bioavailability. 47. What are solvates in the context of polymorphism? A: Solvates are crystals that include solvent molecules within their structure, influencing the physical properties of the solid. 48. How is the melting point related to the purity of a compound? A: A purer compound will have a narrower and higher melting point. 49. Why is polymorphism important for the drug Ritonavir? A: A polymorphic change caused the drug to become less bioavailable, impacting its therapeutic effectiveness. 50. What is the significance of particle size in polymorphism? A: Polymorphic transitions can cause changes in particle size, affecting drug dissolution and bioavailability.