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href="../19290/introduction-to-biochemistry--1.html">Introduction to biochemistry </a></li><li><a href="../19287/proteins-enzymes--1.html">Proteins & enzymes </a></li><li><a href="../19291/lipids-1.html">Lipids</a></li><li><a href="../19299/carbohydrates--1.html">Carbohydrates </a></li><li><a href="../19305/vitamins--1.html">Vitamins </a></li><li><a href="../19313/biochemistry-the-environment--1.html">Biochemistry & the environment </a></li><li><a href="../19336/proteins-enzymes-ahl--1.html">Proteins & enzymes (AHL) </a></li><li><a href="../19347/nucleic-acids--1.html">Nucleic acids </a></li><li><a href="../19361/biological-pigments--1.html">Biological pigments </a></li><li><a href="../19366/stereochemistry-in-biomolecules-1.html">Stereochemistry in biomolecules</a></li></ul></li><li><a href="../19390/option-c--1.html" class="father">Option C </a><ul class="level-2"><li><a href="../19391/energy-sources-1.html">Energy sources</a></li><li><a href="../19407/fossil-fuels-1.html">Fossil fuels</a></li><li><a href="../19411/nuclear-fusion-nuclear-fission-reactions-1.html">Nuclear fusion & nuclear fission reactions</a></li><li><a href="../19429/solar-energy-1.html">Solar energy</a></li><li><a href="../19437/environmental-impact-global-warming-1.html">Environmental impact - global warming</a></li><li><a href="../19453/electrochemistry-rechargeable-batteries-fuel-cells-1.html">Electrochemistry, rechargeable batteries & fuel cells</a></li><li><a href="../19458/nuclear-fusion-fission-hl--1.html">Nuclear fusion & fission (HL) </a></li><li><a href="../19470/photovoltaic-cells-and-dsscs-1.html">Photovoltaic cells and DSSCs</a></li></ul></li><li><a href="../19078/option-d-1.html" class="father">Option D</a><ul class="level-2"><li><a href="../19079/pharmaceutical-products-drug-action--1.html">Pharmaceutical products & drug action </a></li><li><a href="../19158/aspirin-penicillin--1.html">Aspirin & penicillin </a></li><li><a href="../19174/opiates-1.html">Opiates</a></li><li><a href="../19184/ph-regulation-of-the-stomach-1.html">pH regulation of the stomach</a></li><li><a href="../19194/antiviral-medications--1.html">Antiviral medications </a></li><li><a href="../19211/environmental-impact-of-some-medications-1.html">Environmental impact of some medications</a></li><li><a href="../19254/taxol-a-chiral-auxiliary-case-study-1.html">Taxol - a chiral auxiliary case study</a></li><li><a href="../19258/nuclear-medicine--1.html">Nuclear medicine </a></li><li><a href="../19273/drug-detection-analysis--1.html">Drug detection & analysis </a></li></ul></li></ul></li><li><a href="../16592/practical-scheme-of-work-ia--1.html">Practical scheme of work & IA </a><ul class="level-1"><li><a href="../16682/internal-assessment-1.html" class="father">Internal Assessment</a><ul class="level-2"><li><a href="../18892/scaffolding-the-investigation-1.html">'Scaffolding' the investigation</a></li><li><a href="../18896/timing-organisation--1.html">Timing & organisation </a></li><li><a href="../18905/choosing-the-research-question-1.html">Choosing the research question</a></li><li><a href="../18946/personal-engagement-1.html">Personal engagement</a></li><li><a href="../18950/exploration-1.html">Exploration</a></li><li><a href="../18957/analysis-1.html">Analysis</a></li><li><a href="../18965/evaluation-1.html">Evaluation</a></li><li><a href="../18966/communication-1.html">Communication</a></li><li><a href="../19882/internal-standardization-of-the-ia-1.html">Internal standardization of the IA</a></li><li><a href="../19901/submitting-the-samples-for-moderation-2.html">Submitting the samples for moderation</a></li><li><a href="../33754/ten-suggestions-for-ias-using-secondary-data-1.html">Ten suggestions for IAs using secondary data</a></li><li><a href="../37544/gaining-full-marks-for-a-databased-ia--1.html">Gaining full marks for a databased IA </a></li><li><a href="../19506/ia-example-marking-exercise--1.html">IA example & marking exercise </a></li><li><a href="../23929/genuine-examples-of-moderated-ia-reports-1.html">Genuine examples of moderated IA reports</a></li><li><a href="../25234/examples-of-teacher-marked-ia-reports--1.html">Examples of teacher-marked IA reports </a></li><li><a href="../37542/history-of-internal-assessment-1.html">History of Internal Assessment</a></li></ul></li><li><a href="../16598/mandatory-laboratory-components-1.html" class="father">Mandatory laboratory components</a><ul class="level-2"><li><a href="../16613/formula-of-magnesium-oxide--1.html">Formula of magnesium oxide </a></li><li><a href="../16612/determining-the-mr-of-an-unknown-gas-1.html">Determining the <i>M</i><sub>r</sub> of an unknown gas</a></li><li><a href="../16615/acid-base-titrations--1.html">Acid-base titrations </a></li><li><a href="../16616/a-green-acid-base-practical-1.html">A green acid-base practical</a></li><li><a href="../16617/analysis-of-aspirin-tablets-1.html">Analysis of aspirin tablets</a></li><li><a href="../16618/caco3-in-egg-shells-1.html">CaCO<sub>3</sub> in egg shells</a></li><li><a href="../16644/enthalpy-changes-1.html">Enthalpy changes</a></li><li><a href="../16631/reaction-rates-1.html">Reaction rates</a></li><li><a href="../16635/rate-dependent-factors-1.html">Rate-dependent factors</a></li><li><a href="../16636/determining-ea-for-a-reaction-1.html">Determining <i>E</i><sub>a</sub> for a reaction</a></li><li><a href="../16637/iodination-of-propanone-1.html">Iodination of propanone</a></li><li><a href="../18144/titrations-with-a-ph-meter-1.html">Titrations with a pH meter</a></li><li><a href="../18355/redox-titration-with-kmno4--1.html">Redox titration with KMnO<sub>4</sub> </a></li><li><a href="../16640/voltaic-cells-1.html">Voltaic cells</a></li><li><a href="../16659/3-d-molecular-modelling--1.html">3-D molecular modelling </a></li></ul></li><li><a href="../17168/other-good-practicals-1.html" class="father">Other good practicals</a><ul class="level-2"><li><a href="../17196/common-chemical-reactions-1.html">Common chemical reactions</a></li><li><a href="../227/elements-oxides-of-the-third-period--1.html">Elements & oxides of the third period </a></li><li><a href="../17239/the-halogens-1.html">The halogens</a></li><li><a href="../17162/boiling-points-of-mixtures-1.html">Boiling points of mixtures</a></li><li><a href="../17170/polarity-of-molecules-1.html">Polarity of molecules</a></li><li><a href="../18083/le-chateliers-principle--1.html">Le Chatelier's principle </a></li><li><a href="../19582/determining-kc-for-an-esterification-reaction-1.html">Determining <i>K</i><sub>c</sub> for an esterification reaction</a></li><li><a href="../18164/redox-reactions-of-vanadium--1.html">Redox reactions of vanadium </a></li><li><a href="../18351/chlorine-in-swimming-pools--1.html">Chlorine in swimming pools </a></li><li><a href="../18178/analysis-of-cuii-ions-in-solution--1.html">Analysis of Cu(II) ions in solution </a></li><li><a href="../18179/percentage-of-copper-in-brass-1.html">Percentage of copper in brass</a></li><li><a href="../18356/electrolytic-cells--1.html">Electrolytic cells </a></li><li><a href="../18598/reactions-of-organic-compounds-1.html">Reactions of organic compounds</a></li><li><a href="../18752/hydrolysis-of-halogenoalkanes-1.html">Hydrolysis of halogenoalkanes</a></li><li><a href="../18784/preparation-of-13-dinitrobenzene--1.html">Preparation of 1,3-dinitrobenzene </a></li><li><a href="../19022/determination-of-an-organic-structure-1.html">Determination of an organic structure</a></li><li><a href="../19887/preparation-of-nylon-66-1.html">Preparation of nylon 6,6</a></li><li><a href="../19343/determination-of-vitamin-c-content--1.html">Determination of vitamin C content </a></li><li><a href="../19342/hydrolysis-of-starch--1.html">Hydrolysis of starch </a></li><li><a href="../19159/preparation-purification-of-aspirin--1.html">Preparation & purification of aspirin </a></li></ul></li><li><a href="../18851/ict-in-practical-work-1.html" class="father">ICT in practical work</a><ul class="level-2"><li><a href="../18852/data-logging--1.html">Data logging </a></li><li><a href="../18853/software-for-graph-plotting--1.html">Software for graph plotting </a></li><li><a href="../18854/spreadsheets-for-data-processing--1.html">Spreadsheets for data processing </a></li><li><a href="../18855/databases-1.html">Databases</a></li><li><a href="../18856/computer-modelling-simulations--1.html">Computer modelling & simulations </a></li></ul></li><li><a href="../16594/group-4-project-1.html" class="father">Group 4 Project</a><ul class="level-2"><li><a href="../16595/practicalities-1.html">Practicalities</a></li><li><a href="../16596/reflective-statement--2.html">Reflective statement </a></li></ul></li><li><a href="../16666/a-new-laboratory-1.html">A new laboratory?</a></li></ul></li><li><a href="../16284/exams-1.html">Exams</a><ul class="level-1"><li><a href="../16286/essential-facts-1.html" class="father">Essential Facts</a><ul class="level-2"><li><a href="../16287/objectives-command-terms-1.html">Objectives & command terms</a></li><li><a href="../16288/grade-descriptors-1.html">Grade descriptors</a></li><li><a href="../16289/grade-boundaries-1.html">Grade boundaries</a></li></ul></li><li><a href="../16302/paper-1-multiple-choice-1.html" class="father">Paper 1 (Multiple Choice)</a><ul class="level-2"><li><a href="../16303/advice-to-students-paper-1-1.html">Advice to students (Paper 1)</a></li><li><a href="../31515/practice-paper-1-exams-1.html">Practice Paper 1 exams</a></li></ul></li><li><a href="../16305/paper-2-1.html" class="father">Paper 2</a><ul class="level-2"><li><a href="../16306/advice-to-students-paper-2-1.html">Advice to students (Paper 2)</a></li><li><a href="../16307/areas-of-difficulty-1.html">Areas of difficulty</a></li></ul></li><li><a href="../16313/paper-3--1.html" class="father">Paper 3 </a><ul class="level-2"><li><a 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href="../16323/retaking-the-exam-1.html">Retaking the exam</a></li></ul></li><li><a href="../16325/faqs-1.html">FAQs</a></li></ul></li><li><a href="../3147/ib-core-1.html">IB Core</a><ul class="level-1"><li><a href="../3149/learner-profile-1.html">Learner Profile</a></li><li><a href="../21735/extended-essays--1.html" class="father">Extended Essays </a><ul class="level-2"><li><a href="../21736/overview--1.html">Overview </a></li><li><a href="../21780/responsibilities-1.html">Responsibilities</a></li><li><a href="../21790/resources-1.html">Resources</a></li><li><a href="../21800/research-1.html">Research</a></li><li><a href="../21804/writing-the-essay-1.html">Writing the essay</a></li><li><a href="../21810/assessment-1.html">Assessment</a></li><li><a href="../22434/summary-of-advice--1.html">Summary of advice </a></li><li><a href="../25272/faqs--1.html">FAQs </a></li></ul></li><li><a href="../307/theory-of-knowledge-tok-1.html" class="father">Theory of Knowledge (TOK)</a><ul class="level-2"><li><a href="../41171/the-12-tok-concepts-1.html">The 12 TOK concepts</a></li><li><a href="../3507/why-tok-chemistry-1.html">Why TOK & Chemistry?</a></li><li><a href="../3505/a-modern-paradigm-1.html">A modern paradigm</a></li></ul></li></ul></li><li><a href="../17783/fast-track-to-tests-questions-1.html">Fast track to tests & questions</a><ul class="level-1"><li><a href="../17784/sl-multiple-choice-tests-on-individual-topics-1.html">SL Multiple choice tests on individual topics</a></li><li><a href="../24351/sl-multiple-choice-quizzes-on-sub-topics-1.html">SL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31519/sl-practice-paper-1-exams-1.html">SL Practice Paper 1 exams</a></li><li><a href="../17786/sl-questions-on-each-sub-topic-1.html">SL Questions on each sub-topic</a></li><li><a href="../20431/sl-paper-3-section-a-questions-1.html">SL Paper 3 Section A questions</a></li><li><a href="../17792/sl-questions-on-the-options-1.html">SL Questions on the options</a></li><li><a href="../24897/sl-quizzes-on-option-sub-topics--1.html">SL Quizzes on option sub-topics </a></li><li><a href="../17785/hl-multiple-choice-tests-on-individual-topics-1.html">HL Multiple choice tests on individual topics</a></li><li><a href="../24352/hl-multiple-choice-quizzes-on-sub-topics-1.html">HL Multiple choice 'quizzes' on sub-topics</a></li><li><a href="../31520/hl-practice-paper-1-exams--1.html">HL Practice Paper 1 exams </a></li><li><a href="../17787/hl-questions-on-each-sub-topic--1.html">HL Questions on each sub-topic </a></li><li><a href="../20428/hl-paper-3-section-a-questions-1.html">HL Paper 3 Section A questions</a></li><li><a href="../17793/hl-questions-on-the-options-1.html">HL Questions on the options</a></li><li><a href="../24973/hl-quizzes-on-option-sub-topics-1.html">HL Quizzes on option sub-topics</a></li><li><a href="../41573/printable-versions-of-written-tasks--1.html">Printable versions of written tasks </a></li></ul></li><li><a 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href="../24867/proteins-enzymes-hl-answers-1.html" title="Proteins & enzymes (HL) answers">Proteins & enzymes (HL) answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19347/nucleic-acids--1.html" title="Nucleic acids ">Nucleic acids </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../24993/mc-test-nucleic-acids-1.html" title="MC test: Nucleic acids">MC test: Nucleic acids</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19360/nucleic-acids-questions--1.html" title="Nucleic acids questions ">Nucleic acids questions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../24869/nucleic-acids-answers-1.html" title="Nucleic acids answers">Nucleic acids answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa 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biomolecules</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25034/mc-test-stereochemistry-in-biomolecules--1.html" title="MC test: Stereochemistry in biomolecules ">MC test: Stereochemistry in biomolecules </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19373/stereochemistry-in-biomolecules-questions-1.html" title="Stereochemistry in biomolecules questions">Stereochemistry in biomolecules questions</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../24871/stereochemistry-in-biomolecules-answers--1.html" title="Stereochemistry in biomolecules answers ">Stereochemistry in biomolecules answers </a></li></ul></ul><li class=" parent" style="padding-left: 0px"><i class="expander fa fa-caret-right "></i><a href="../19390/option-c--1.html" title="Option C ">Option C </a></li><ul class="level-1 "><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19391/energy-sources-1.html" title="Energy sources">Energy sources</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25112/mc-test-energy-sources-1.html" title="MC test: Energy sources">MC test: Energy sources</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19404/energy-sources-questions--1.html" title="Energy sources questions ">Energy sources questions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25025/energy-sources-answers-1.html" title="Energy sources answers">Energy sources answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19407/fossil-fuels-1.html" title="Fossil fuels">Fossil fuels</a></li><ul class="level-2 "><li class="" 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href="../25188/mc-test-nuclear-fusion-nuclear-fission-reactions-1.html" title="MC test: Nuclear fusion & nuclear fission reactions">MC test: Nuclear fusion & nuclear fission reactions</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19421/nuclear-fusion-nuclear-fission-questions-1.html" title="Nuclear fusion & nuclear fission questions">Nuclear fusion & nuclear fission questions</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25180/nuclear-fusion-nuclear-fission-answers-1.html" title="Nuclear fusion & nuclear fission answers">Nuclear fusion & nuclear fission answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19429/solar-energy-1.html" title="Solar energy">Solar energy</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a 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global warming</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19450/environmental-impact-global-warming-questions--1.html" title="Environmental impact - global warming questions ">Environmental impact - global warming questions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25190/environmental-impact-global-warming-answers-1.html" title="Environmental impact - global warming answers">Environmental impact - global warming answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19453/electrochemistry-rechargeable-batteries-fuel-cells-1.html" title="Electrochemistry, rechargeable batteries & fuel cells">Electrochemistry, rechargeable batteries & fuel cells</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a 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title="Nuclear fusion & fission (HL) ">Nuclear fusion & fission (HL) </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25269/mc-test-nuclear-fusion-nuclear-fission-hl-1.html" title="MC test: Nuclear fusion & nuclear fission (HL)">MC test: Nuclear fusion & nuclear fission (HL)</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19468/nuclear-fusion-fission-reactions-hl-questions--1.html" title="Nuclear fusion & fission reactions (HL) questions ">Nuclear fusion & fission reactions (HL) questions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25205/nuclear-fusion-fission-reactions-hl-answers-1.html" title="Nuclear fusion & fission reactions (HL) answers">Nuclear fusion & fission reactions (HL) answers</a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a 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title="Option D">Option D</a></li><ul class="level-1 "><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19079/pharmaceutical-products-drug-action--1.html" title="Pharmaceutical products & drug action ">Pharmaceutical products & drug action </a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25440/mc-test-pharmaceutical-products-drug-action-1.html" title="MC test: Pharmaceutical products & drug action">MC test: Pharmaceutical products & drug action</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19154/pharmaceutical-products-drug-action-questions--1.html" title="Pharmaceutical products & drug action questions ">Pharmaceutical products & drug action questions </a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a 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">Aspirin & penicillin answers </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19174/opiates-1.html" title="Opiates">Opiates</a></li><ul class="level-2 "><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25494/mc-test-opiates-1.html" title="MC test: Opiates">MC test: Opiates</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../19176/opiates-questions-1.html" title="Opiates questions">Opiates questions</a></li><li class="" style="padding-left: 28px"><i class="expander fa fa-caret-right "></i><a href="../25356/opiates-answers--1.html" title="Opiates answers ">Opiates answers </a></li></ul><li class=" parent" style="padding-left: 14px"><i class="expander fa fa-caret-right "></i><a href="../19184/ph-regulation-of-the-stomach-1.html" title="pH regulation of the stomach">pH regulation of the stomach</a></li><ul class="level-2 "><li 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</div><section id="main-content"><div id="toc-1672969656" class="toc"><a href="#" class="toc-switcher" title="Show table of contents"><small><i class="fa fa-reorder"></i> Table of contents <span class="pull-right"><i class="fa fa-chevron-down"></i></span></small></a></div><h1><img class="ico" src="../../../img/icons/standard-1.png"> <img class="ico" src="../../../img/icons/higher-1.png"> A.4 Liquid crystals (2 hours)</h1><hr class="hidden"><div class="pinkBg"><div><h2>Pause for thought</h2><p>The Nature of Science section for this sub-topic uses Reinitzer’s discovery of liquid crystals as an example of serendipity. In 1888 Reinitzer synthesised a new compound - cholesteryl benzoate.</p><p style="text-align: center;"><img alt="" class="noborder" src="../../../ib/chemistry/images/2014%20Core%20%26%20AHL/Topics%204%20%26%2014/cholesterylbenzoate-1-1200x561.png" style="width: 550px; height: 257px;"></p><p style="text-align: center;">cholesteryl benzoate (Image from Wikimedia commons)</p><p>In order to show that it was pure he needed to determine the melting point and was surprised to find that it appeared to have two different melting points. At 145.5 <sup>o</sup>C the white solid crystals melted into a cloudy liquid, which remained stable when heated further until178.5 <sup>o</sup>C. At this point the cloudiness disappeared to form a clear transparent liquid.</p><hr class="hidden"><p style="text-align: center;"><img alt="" class="noborder" src="../../../ib/chemistry/images/2014-Options/Option-A/cholesteryl-benzoate-145.5.jpg" style="width: 252px; height: 303px;"> <img alt="" class="noborder" src="../../../ib/chemistry/images/2014-Options/Option-A/cholesteryl-benzoate-178.5.jpg" style="width: 252px; height: 305px;"></p><p>In fact it was one of his colleagues, Otto Lehmann, who realised that whilst the clear liquid had the isotopic properties and the disordered state of all liquids the cloudy liquid was a new state of matter intermediate between a solid and a liquid. He coined the label ‘liquid crystal’ to describe this new state of matter in which the properties depend upon direction even though the state is liquid.</p><p>As is sometimes the case with serendipitous discoveries it was initially seen as an interesting but not particularly useful fact and no real advances in the chemistry of liquid crystals was made until about 80 years later. The first commercial use of liquid crystal displays was not until the 1960s where they became incorporated into Swiss watches. Since then they have almost become ubiquitous and have made cathode rays tubes (which originally produced the pictures in televisions) virtually obsolete.</p><hr class="hidden"></div></div><hr class="hidden"><div class="box"><div><h2 id="anchor-2">Nature of science</h2><p>The discovery of liquid crystals is a good example of serendipity in science. They were discovered accidently by the Austrian botanist and chemist Friedrich Reinitzer (1857 - 1927) whilst experimenting on cholesteryl benzoate in 1888.</p><hr class="hidden"></div></div><hr class="hidden"><div class="box"><table align="left" border="0" cellpadding="10" cellspacing="0"><tbody><tr><td style="width: 50%;" valign="top"><div class="yellowBg"><div><h2 id="anchor-3"><strong><strong>Learning outcomes</strong></strong></h2><p>After studying this topic students should be able to:</p><p><strong><strong>Understand:</strong></strong></p><ul><li>Liquid crystals are fluids with physical properties (electrical, optical and elasticity) which depend upon molecular orientation to a fixed axis in the material.</li><li>Thermotropic liquid crystals are pure substances that show liquid crystal behaviour over a range of temperature.</li><li>Lyotropic liquid crystals are solutions which show the liquid-crystal state over a range of concentrations.</li><li>The nematic liquid crystal phase is characterized by rod-shaped molecules that are distributed randomly but on average align in the same direction.</li></ul><hr class="hidden"><p><strong>Apply their knowledge to:</strong></p><ul><li>Discuss the properties required for a substance to be used in liquid-crystal displays (LCD).</li><li>Explain liquid-crystal behaviour on a molecular level.</li></ul></div></div></td><td style="width: 50%;" valign="top"><h4><b><span style="font-weight: normal;"></span></b></h4><div class="yellowBg"><div><h4><b><span style="font-weight: normal;"><strong>Clarification notes</strong></span></b></h4><p>The properties needed for liquid crystals include: chemically stability, a phase that is stable over a suitable temperature range, polar (so they can change<br>orientation when an electric field is applied) and rapid switching speed.</p><hr class="hidden"><p>Soapy water is an example of lyotropic liquid crystals. The biphenyl nitriles are examples of thermotropic liquid crystals.</p><hr class="hidden"><p>Limit liquid crystal behaviour to the biphenyl nitriles.</p><hr class="hidden"><p>Discussion of smectics and other liquid crystals is not required.</p><hr class="hidden"><h4 id="anchor-5">International-mindedness</h4>The production of many electronic goods is concentrated in areas of the world where poor working conditions may prevail. This raises the issue as to whether there should be internationally accepted labour standards for all workers, and, if so, what implications this would have on the price of consumer goods?</div></div></td></tr></tbody></table></div><hr class="hidden"><div class="box"><table align="left" border="0" cellpadding="10" cellspacing="0"><tbody><tr><td style="width: 50%;" valign="top"><h2><span style=""><b><span style="font-weight: normal;"><strong>Teaching tips</strong></span></b></span></h2><p>This is a fairly descriptive topic, although it is possible for students to make a simple LCD (see other resources below). One way to start might be by getting students to list where they have seen LCDs in use so they realize their importance. Stress that the liquid crystal state is another state of matter and explain that it is in between the solid and liquid phase so that the molecules in the liquid still have some orientation rather than being randomly distributed. Make sure your students understand the difference between lyotropic and thermotropic liquid crystals with at least one example for each.</p><p>Focus then on the biphenyl nitriles. Using their structures explain that: 1. They contain polar groups so that the intermolecular forces can align in a common direction. 2. The benzene rings ensure that the molecules are rigid and so more rod shaped and 3. The long chain alkyl group ensures that the molecules cannot pack too closely which helps to maintain the liquid crystal state.</p><p>Finally explain how liquid crystal displays work stressing the idea of twisted nematic geometry and the interaction of liquid crystals with plane-polarized light. It is worth looking at the advantages and disadvantages of LCDs. It should then be fairly obvious that the properties needed by liquid crystals for use in an LCD are chemical stability, polar nature, stability in the liquid crystal phase over a reasonable temperature range and rapid switching speed (ability to orientate quickly).</p></td><td style="width: 50%;" valign="top"><h4><b><span style="font-weight: normal;"><strong>Study Guide</strong></span></b></h4><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"><a href="http://ukcatalogue.oup.com/product/education/international/ibdiploma/studyguides/9780199151424.do?"><b><span style="font-weight: normal;"><img alt="" class="left noborder" src="../../../ib/chemistry/images/2014%20Basic%20information/New%20cover.jpg" style="width: 67px; height: 96px;"></span></b></a></p><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"></p><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"></p><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"></p><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"></p><hr class="hidden"><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"><b><span style="font-weight: normal;">Pages </span></b><span style="font-weight: normal;">114 & 115</span></p><hr class="hidden"><h2>Questions</h2><p>For ten 'quiz' questions (for quick testing of knowledge and understanding with the answers explained) see <a href="../26133/mc-test-liquid-crystals-1.html" title="Options » Option A » Liquid crystals » MC test: Liquid crystals">MC test: Liquid crystals</a>.</p><p>For short-answer questions see <a href="../19592/liquid-crystals-questions--1.html" title="Options » Option A » Liquid crystals » Liquid crystals questions ">Liquid crystals questions </a>together with the worked answers on a separate page <a href="../26054/liquid-crystals-answers-1.html" title="Options » Option A » Liquid crystals » Liquid crystals answers">Liquid crystals answers</a>.</p><hr class="hidden"><h4><span style=""><b><span style="font-weight: normal;"><strong>Vocabulary list</strong></span></b></span></h4><p><span style=""><span style="font-weight: normal;">serendipity<br>thermotropic<br>lyotropic<br>nematic liquid crystal phase<br>twisted nematic geometry<br>liquid crystal display (LED)<br>biphenyl nitrile<br>smectic phase</span></span></p><p style="margin: 0px 0px 1em; padding: 0px; color: rgb(0, 0, 0); font-size: 1em;"></p></td></tr></tbody></table></div><hr class="hidden"><div class="greenBg"><div><h2 id="header-13">Teaching slides</h2><p>Teachers may wish to share these slides with students for learning or for reviewing key concepts.</p><div id="myCarousel-14" class="carousel slide" data-id="665"><!-- Carousel items --><div class="carousel-inner"><div class="active item"><a class="fancy" href="../../../tib-galleries/3-665/a4-1.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-1.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-2.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-2.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-3.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-3.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-4.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-4.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-5.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-5.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-6.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-6.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-7.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-7.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div><div class="item"><a class="fancy" href="../../../tib-galleries/3-665/a4-8.png" rel="gallery-665" title=""><img alt="" src="files/tib-galleries/3-665/a4-8.png"></a><div class="carousel-caption"><p>Liquid crystals: </p></div></div></div><!-- Carousel nav --><a class="carousel-control left" href="#myCarousel-14" data-slide="prev">‹</a><a class="carousel-control right" href="#myCarousel-14" data-slide="next">›</a><div class="tib-indicators"><img class="" title="Click to view" style="margin: 10px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-1-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-2-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-3-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-4-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-5-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-6-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-7-thumb128.jpg"><img class="" title="Click to view" style="margin: 5px 4px; width: 48px; height: 48px;" alt="" src="files/tib-galleries/3-665/a4-8-thumb128.jpg"></div></div><p> </p></div></div><hr class="hidden"><div class="pinkBg"><h2>Other resources</h2><p><strong>1.</strong> A good article from the official website of the Nobel Prize on <a href="Browse server to select file" target="_blank" title="Videos"><img class="ico" src="../../../img/icons/video-1.png"><span class="anchor" id="video-1" name="video-1"> </span> The history and properties of liquid crystals</a>. It also includes some embedded informative short videos.</p><p><strong>2. </strong>A lecturer from the University of Hull explains liquid crystal displays using some wool, pasta, a bottle of water, a hair dryer and some stair gates. Who says you need expensively equipped labs to explain chemistry! This is real supermarket chemistry.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/iJks-gapzkk?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/iJks-gapzkk" target="_blank" title="Videos"><img class="ico" src="../../../img/icons/video-1.png"><span class="anchor" id="video-2" name="video-2"> </span> Explaining LCDs</a></p><hr class="hidden"><p><strong>3.</strong> Fancy building your own liquid crystal display? This video by Ben Krasnow describes liquid crystals and what happens when you put them between polarizers. It includes a good description of how LCDs work.</p><p style="text-align: center;"><iframe allowfullscreen="" frameborder="0" height="280" src="//www.youtube.com/embed/d4QFNWBSZYg?rel=0" width="360"></iframe></p><p style="text-align: center;"><a href="http://youtu.be/d4QFNWBSZYg" target="_blank" title="Videos"><img class="ico" src="../../../img/icons/video-1.png"><span class="anchor" id="video-3" name="video-3"> </span> Building your own liquid crystal display</a></p><hr class="hidden"><p style="text-align: center;"></p></div></section></article><section id="media-extras"><div class="page-actions no-print navbar inline hidden-desktop"><div class="navbar-inner"><ul class="nav"><li><a class="presentation" href="#" onclick="return false;"><i class="fa fa-desktop"></i></a></li><li><a class="print-section-blog" href="#" onclick="return false;"><i class="fa fa-print"></i></a></li><li><a class="page-bookmarker" data-ticket="IB Docs (2) Team" data-pid="19580" href="#" onclick="return false;"><i class="fa fa-star"></i></a></li><li><a class="personal-notes" href="#" onclick="return false;"><i class="fa fa-file-text"></i></a></li><li><a class="" data-toggle="modal" href="#modal-feedback" onclick="return false;"><i class="fa fa-envelope-o"></i></a></li><li class="dropdown"><a class="dropdown-toggle" data-toggle="dropdown" data-target="#" href="#"><i class="fa fa-share-alt"></i></a><ul class="dropdown-menu" role="menu"><li><a class="" target="_blank" title="Share on Twitter" href="https://twitter.com/share?text=%22Liquid+crystals%22+-+via+%40InThinker+%23chemistry%0A&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F19580%2Fliquid-crystals"><i class="fa fa-twitter-square"></i><span>Twitter</span></a></li><li><a class="" target="_blank" title="Share on Facebook" href="https://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F19580%2Fliquid-crystals&t=Liquid+crystals"><i class="fa fa-facebook-square"></i><span>Facebook</span></a></li><li><a class="" href="http://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F19580%2Fliquid-crystals"><i class="fa fa-linkedin-square"></i><span>LinkedIn</span></a></li><li><a class="" href="https://plus.google.com/share?url=https%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F19580%2Fliquid-crystals"><i class="fa fa-google-plus-square"></i><span>Google +</span></a></li><li><a class="" href="mailto:?subject=Liquid crystals&body=The Nature of Science section for this sub-topic uses Reinitzer’s discovery of liquid crystals as an example of serendipity. In 1888 Reinitzer synthesised a new compound - cholesteryl benzoate.cholesteryl benzoate (Image...%0Ahttps%3A%2F%2Fwww.thinkib.net%2Fchemistry%2Fpage%2F19580%2Fliquid-crystals"><i class="fa fa-envelope"></i><span>Email</span></a></li></ul></li><li><a class="" href="chemistry/teaching-materials"><i class="fa fa-puzzle-piece colored"></i></a></li></ul></div></div><div style="border-top: solid 1px #eee;border-bottom: solid 1px #eee;padding: 4px 0 4px 0;line-height: 1em;color: #666;font-size: .8em"><small><em>All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Any unauthorised copying or posting of materials on other websites is an infringement of our copyright and could result in your account being blocked and legal action being taken against you.</em></small></div></section><section id="comments"></section></div><!-- /#main-column -->
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