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Microscale Chemistry: An Overview Professor Chan Wing-Hong Department of Chemistry, HKBU PowerPoint Presentation
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Microscale Chemistry: An Overview Professor Chan Wing-Hong Department of Chemistry, HKBU

Microscale Chemistry: An Overview Professor Chan Wing-Hong Department of Chemistry, HKBU

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Microscale Chemistry: An Overview Professor Chan Wing-Hong Department of Chemistry, HKBU

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  1. Microscale Chemistry: An Overview Professor Chan Wing-Hong Department of Chemistry, HKBU • Definition and characteristics of microscale chemistry • Apparatus and techniques for microscale chemistry • Designing microscale activities with different pedagogic approaches

  2. What is “microscale chemistry”? Microscale (or small scale) chemistry carried out on a reduced scale using small quantities of chemicals and often (but not always) simple equipment. John Skinner Conducting chemical investigations with reagents amounted to 1/10 to 1/1000 of that of conventional laboratory using microscale apparatus

  3. Why microscale chemistry? Advantages relating to laboratory management: The small quantities of chemicals and simple equipment reduces the running cost of the laboratory works; The wastes generated from the laboratory works can be minimised which makes the disposal afterwards easier; Safety hazards are likely reduced and many laboratory activities could be performed in open bench; Many microscale experiments can be completed in shorter time; and Oftentimes, plastic apparatus can be used to replace glasswares, thus breakages are minimised.

  4. How can microscale chemistry enrich the learning experiences of students in chemical laboratory works As the running cost of the laboratory works is greatly reduced, more experiments can be integrated into the curriculum. Students can receive more training in laboratory works. As the process of microscale experiment often takes place very quickly, students benefit from the demand of careful observation and interpretation. By minimising waste, microscale chemistry encourages students to use chemicals responsibly, an issue in tune with environmental concerned. As there is no standard set of apparatus for conducting microscale experiment, innovated thinking for planning laboratory activities can be nurtured for students.

  5. (2) Apparatus and techniques for microscale chemistry

  6. Plastic Petri dishes As a container to prepare small amount of gas and to study its chemical properties.

  7. Syringe experiments By A. Koehler

  8. Microscale gas chemistry The In-Syringe Method is used for generating the following gases: carbon dioxide, CO2hydrogen, H2oxygen, O2nitric oxide, NO, and nitrogen dioxide, NO2ammonia, NH3ethyne, C2H2sulphur dioxide, SO2chlorine, Cl2nitrogen, N2 silane, SiH4hydrogen sulphide, H2S

  9. Plastic disposal pipettes This versatile apparatus may be used for storing solutions, after some modifications, it can be used a mini-reaction vessel and an electrolysis apparatus.

  10. Glasswares for microscale organic chemistry

  11. Well-plates Different versions of well-plates are available in the market. Well-plates can be used for studying chemical equilibria (i.e. complexation and precipitate formation) and colorimetric experiments.

  12. Multi-holes well-plates for direct comparison of an array of reactions: Precipitation Reactions/Redox Reactions C. Gruvberg/

  13. J. D. Bradley

  14. Reduction of CuO by hydrogen J. D. Bradley

  15. Microburette Each drop of titrant delivered by the microburette is about 0.02 mL. The set-up is particularly useful if expensive reagents have to be employed.

  16. Titration curves can be obtained by the colour of the indicator K. Ogino

  17. Construction of titration curves

  18. Four Channels LED-Based Photometer The equipment is ideal for quantitative work.

  19. LED-based Photometer Reason for choosing LED as light source • LED emits radiation in the visible region

  20. Table 1.1 Summary of LED’s colour, peak emission wavelength and spectral bandwidth

  21. Photometric determination of ionic, organic and gaseous species by the photometer Determination of copper in wastewater Determination of iron content in mineral tablets Analysis of lead in soil samples Analysis of airborne NO2 and SO2 Analysis of indoor air pollutant – formaldehyde Analysis of phenol in wastewater

  22. (3)Designing microscale activities with different pedagogic approaches Case study approach Guide-discovery approach Defining a chemical problem Multi-leveled approach Traditional cookbook type approach

  23. Guided-discovery Approach The practical works can be arranged in such a way that : • Put up some key questions to draw the attention of the students. • Remind the students to mark down the key observations of the activity. • Assist them to interpret the experimental findings and to draw the conclusion.

  24. Multi-leveled approach The breath and depth of the treatment of many chemical principles can be modulated according to the background of the students (i.e. CE versus AL students). Even within the same class of students, the motivation and interests of individual can be different. It does make sense to plan a series of activities with increase in “sophistication” to cater the aspiration of different students. A simple strategy is to design a laboratory activity at three levels, viz. qualitative, semi-quantitative and quantitative approach.

  25. Demonstrating Environmental Chemistry with Case Studies Air Pollution by Nitrogen Oxides (NOx) Examination of Lead Contamination Treatment of Industrial copper Wastewater Degradation of Phenols in Wastewater Samples

  26. Template for constructing cases • Topic directing questions • Experimental design & setup • Experimental operations and observations • Learning outcome from the activity • Presentation of the key issues of the activity

  27. Case one Air Pollution By Nitrogen Oxides

  28. Topic directing questions: • What pollutants affect air quality? • What are the major sources of NO2? • Why does NOx contribute to the formation of acid rain? • What are the environmental effects of NOx? • What are the health effects of NOx ? • How can air pollutants be sampled? • How will airborne nitrogen oxides be determined?

  29. Experimental design & setup • Emission source: Cu + 4 HNO3 = Cu(NO3)2 + 2 NO2 + 2 H2O Hydrospheric system: water in well plates Terrestrial system: soil in well plates Gaseous samples collection: by placing the passive samplers at different locations Low-cost photometer: used to determine nitrite ion in samples

  30. Inject nitric acid into the well plate containing Copper to generate NO2

  31. After 5 min, to remove the absorption solution from the air sampler

  32. Observe the color of the water at different plates; take 0.1 g soil into a vial & extract with 20 mL water

  33. Filter the solution into a 50 mL volumetric flask & add 2 mL of absorbance solution

  34. Calibration curve can be constructed with a series of standard solution

  35. Learning outcome from the activity Students should understand the environmental effects of NOx, viz. • Acidification of freshwater bodies & terrestrial system • Contribution by nitrogen oxides to the formation of acid rain • Potential change in the composition of terrestrial system

  36. Learning outcome from the activity • Students should gain knowledge on operations of environmental analysis, viz. Determination of pollutants in air (NO2), water and soil (nitrite) • Collection of gaseous sample by a passive sampler • Determination of nitrite ion by photometric method

  37. Key Issues of the Activity • Nature and Sources of the Pollutants • Health and Environmental Effects • Analytical methods for quantification of the pollutant(s) • Trends in nitrogen oxides levels in our city • Measures to trim down the pollutant level

  38. THE END Thank you !