Roll. No.:
Department of Chemical Engineering, IIT-Bombay 400 076
CL240: Materials Technology: Take-Home Quiz (Jayesh Bellare)
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Instructions: Submission Date: 10:30 am on 13 Feb 2003. Submit to: Silicate lab (Mr. Rajeev or Mr. Kamble). When submitting, please sign on roll list available there. Duration of test: not restricted. Calculators are permitted. Maximum marks: 7 (seven plus one bonus mark). Resources permitted: Calculators / Open notes / Open book / Open access to web information (but no sharing of information between students). Write down what resources you used, other than class notes, where you make use of such a resource. Make reasonable engineering assumptions where essential and translate assumptions into limitations to your answers.
Important: Print the first page of this document out on an A4 paper. Answer on additional A4 papers. Tie all papers together. Return this paper, with your signature, as the first sheet together with your answer sheets.
- Calculate the concentration of molecules in a perfectly ordered semectic liquid crystal. Express your answer as a volume percent. Assume that molecules are cylinders with length twice the diameter. Approximate the arrangement of molecules within a given layer as two-dimensional hexagonal close-packed (like carrom coins are arranged at the start of the game), and that the inter-layer spacing (measured between the centers-of-mass of corresponding molecules in adjacent layers) as twice the length of the molecules. [4 marks]
- How is the force measured in the surface forces apparatus? To what resolution is it measured? [2 marks]
- Why are numbers in the ratio of 2 in the clastic scale of particle sizes? [1 mark]
- [Open-ended bonus question.] The attached advertisement appeared recently in the press. Discuss the materials science aspects of the “anti-bacteria” property claimed in the ad, i.e., how could this property be imparted to the product, and is the claim justified, especially at the price mentioned? Or is it a wrong claim? You may search for information on this in any book or journal or on the web, but do not share this information with others giving this test until after the test is submitted by all concerned. [1 mark]
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