Introduction. Roger Woodward. MA.,BSc., ARCS. November Dear Chemistry student,

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1 Introduction Dear Chemistry student, Welcome to this Revision Guide, which I have put together to cover the topics in Option A. Some of the topics in Option A are very up-to-date and new not only to IB students but to many Chemistry teachers and school/high school examination specifications. This means that you will not always find everything included in these topics in traditional school Chemistry textbooks. Remember that some of the topics in Option A require knowledge of the principles in the core syllabus. References to the core guide are given where appropriate. Each section ends with a number of practice questions. These will allow you to check that you are familiar with the material from the specification. I have only provided answers to the questions involving calculations. You will find these on the final pages of this guide. All the answers to questions requiring a written answer can be found by referring to the text in the relevant section of this book. At the time of writing, past papers are not available so I have been unable to include or write my own suitable exam-style questions. Remember: this is not a textbook it is simply a revision guide. By this I mean that I hope that you have already been taught the whole specification in your chemistry classes. I have tried to bring out and simplify the material, but you may need to consult your teacher or a course textbook for more detailed explanations. Having taught the IB HL and SL courses at Sevenoaks School, UK, for over 30 years and at the OSC Revision Courses in Oxford for almost as long, it has been refreshing to see new material coming into the IB syllabus and to learn some new Chemistry myself! I hope that you have enjoyed learning about these fascinating new Chemistry topics and that the guide will help you focus on the main points to bring success in your final exams. Good luck with your revision. Many thanks are due to my colleague Dr Mark Parsons, also from Sevenoaks School, who assisted with the preparation of this guide. Roger Woodward. MA.,BSc., ARCS. November

2 Contents Standard Level Topics A1 Materials science introduction A1.1 Nature of Science/International Mindedness/Theory of Knowledge 10 A1.2 Structure, bonding and properties 10 A2 Metals and inductively coupled plasma spectroscopy A2.1 Metal reduction and reactivity 13 A2.2 Electrolysis calculations 14 A2.3 Alloys 15 A2.4 Magnetic properties of metal compounds 15 A2.5 Inductively coupled plasma detection 16 A2.6 Inductively coupled plasma: Optical emission spectroscopy (ICP-OES) 16 A2.7 Inductively coupled plasma: Mass spectrometry (ICP-MS) 17 A3 Catalysts A3.1 Adsorption (opposite: Desorption) 18 A3.2 Heterogeneous catalysts 18 A3.3 Homogeneous catalysts 18 A3.4 Transition metal compounds 19 A3.5 Zeolites 19 A3.6 Nanoparticles in catalysis 19 A3.7 Catalysts 20 A4 Liquid crystals (LCs) A4.1 Lyotropic LCs 21 A4.2 Liquid crystal displays 21 A5 Polymers A5.1 Thermoplastics 23 A5.2 Thermosetting polymers 23 5

3 Contents A5.3 Elastomers 23 A5.4 Different types of polyethene 23 A5.5 Isotactic and atactic addition polymers 23 A5.6 Plasticisers 24 A5.7 Polystyrene and Styrofoam 24 A5.8 Atom economy 25 A6 Nanotechnology A6.1 Molecular self-assembly 27 A6.2 Molecular assembly 27 A6.3 Carbon nanotubes 27 A6.4 Possible problems with nanotechnology 28 A7 Environmental impact: Plastics A7.1 Dioxins and polychlorinated biphenyls (PCBs) 30 A7.2 Burning plastics 30 A7.3 Volatile plasticisers 31 A7.4 Plastic recycling 31 A7.5 Identification of possible RICs from infra-red spectra 32 Additional Higher Level Topics A8 Superconducting metals and X-Ray crystallography A8.1 Superconductors 33 A8.2 The Meissner effect 33 A8.3 Bardeen-Cooper-Schrieffer (BCS) theory 33 A8.4 Type 1 and type 2 superconductors 33 A8.5 Crystal lattices and unit cells 34 A8.6 Unit cell coordination number 34 A8.7 X-Ray diffraction 34 6 Chemistry - Option A: Materials - 2 nd Edition

4 Contents A8.8 Density of pure metal 35 A8.9 Using the ionic radius to calculate density of metals 35 A9 Condensation polymers A9.1 Addition and condensation polymers 37 A9.2 Kevlar 38 A10 Environmental impact: Heavy metals A10.1 Toxicity 40 A10.2 Removal of heavy metals 40 A10.3 Solubility product 40 A10.4 Polydentate ligands and chelation 41 Sample worked-solutions and answers to questions in this book can be found on page 43. Answers to all other questions raised in the questions proposed in this book can be found by reading the respective chapters. 7

5 A1 Materials science introduction Author s tip Use these margins to write notes. A1 Materials science introduction A1.1 Nature of Science/International Mindedness/Theory of Knowledge Throughout this topic, keep in mind various non-technical aspects associated with the study of materials, for example: How the development of new materials has led to traditionally used materials being replaced. A simple example of this would be the changes in the use of stone, bronze and iron implements by humans throughout history. Which materials were used throughout history by different civilisations? Even though many civilisations may have been separated geographically, the materials they used were often similar. There are various ways to classify materials depending on what we might want to use them for. It is convenient to classify materials into specific types, but it is not always possible for one particular material to perfectly match one particular classification. We could classify a metal on the basis of its electrical conductivity, its specific heat capacity, its tensile strength, its chemical bonding or its ability to oxidise for example. If we then examine a non-metal, some of their properties may even be shared with a metal. A1.2 Structure, bonding and properties Structure: the way that the particles of a material are arranged in (usually) three dimensions. You should know the difference between a giant structure, where a vast number of individual particles are joined in one huge structure with strong bonds throughout (e.g. diamond, sodium chloride) and a molecular structure where individual, strongly covalently bonded molecules are held together loosely by weak London forces. Figure 1_2: Individual polymer chains in a molecular structure the chains do not join each other Bonding: the type of interaction that holds the particles together to assemble the structure ionic, covalent or metallic bonding. Properties: physical attributes as a result of combinations of structure and bonding. Some properties include: Melting point: the stronger the bonding, the higher the melting point. Permeability: a solid will be permeable to moisture if there are gaps between the particles so there is room for water molecules to pass through. Polymers: woven fabrics made from man-made or natural fibres are permeable because there are gaps between the fibres. Many (but not all solid polymers) are impermeable because their polymer chains are non-polar and are usually closely packed together. Paper and card: made of wood or plant fibres. It is permeable because of the gaps between the fibres. Rocks: permeability depends on how they were formed. Limestone and chalk are permeable. Marble and granite are impermeable. In general sedimentary rocks are permeable but once they have been subjected to metamorphic processes become impermeable. This is why limestone is permeable but marble is impermeable. Concrete is often permeable, with a porous structure. It can absorb water like some traditional ceramics (e.g. terracotta, unglazed pottery). Metals and most ceramics have tightly packed particles that make them impermeable. Figure 1_1: Diamond has a giant structure Conductivity: if electrons can flow within a structure, a material can conduct electricity. All metals have a network of delocalised outer shell 10 Chemistry - Option A: Materials - 2 nd Edition

6 A2 Metals and inductively-coupled plasma spectroscopy A2.7 Inductively-coupled plasma: Mass spectrometry (ICP-MS) The ions from the plasma can also be introduced to a mass spectrometer and the m/e ratio measured from the mass spectrum. PRACTICE QUESTIONS: A2 METALS AND INDUCTIVELY-COUPLED PLASMA SPECTROSCOPY 1. Copper and Tin are metallic elements. These metals can be mixed to form bronze. Explain briefly how the following properties are affected by mixing copper and tin: i. The electrical conductivity of the pure metals compared to the electrical conductivity of bronze. ii. The hardness of the pure metals compared to the hardness of bronze. 2. Explain the difference between diamagnetic and paramagnetic compounds in terms of their properties and electronic arrangements. 3. Aluminium is an important metal in modern society. It is found widely distributed over the Earth and is extracted in several stages. Explain the following: i. How is the aluminium in bauxite ore extracted and converted into pure aluminium oxide? (The aluminium oxide is reduced to pure metallic aluminium by adding cryolite, melting the mixture and using electrolysis). ii. Why is cryolite added to the aluminium oxide? iii. The cathode for this process is a graphitelined, steel tank. Explain what is used for the anodes and why they need regular replacing. iv. Write chemical equations for the electrolytic reactions at each electrode. The metal(s) present can be identified from their isotopic masses. Their concentrations can be measured by using a calibration curve technique (as for ICP-OES). 4. Copper is purified by electrolysis. Assuming that the copper is present in solution as Cu 2+ ions, calculate the mass of pure copper that collects at the cathode during the purification process if a current of 2.00 Amps is used for 10 hours. 5. Lead is often found in wastewater from factories that manufacture electronic components, and at battery recycling plants. Its concentration can be measured by using inductively coupled plasma optical emission spectroscopy (ICP- OES). a. Explain briefly the nature of the specific plasma state involved in ICP spectroscopy. b. An ICP-OES calibration curve for lead is shown in the graph below. The range of values was obtained from a variety of domestic water samples. i. Determine the mass of lead ions present in 100cm3 of a solution with a concentration of 800μmol dm -3. ii. Using your answer from part i. explain how you could make up suitable solutions in order to obtain this calibration curve. iii. Two samples of tap water were found to give a count rate 15 and 525 kcps respectively. Explain which sample would be more suitable to analyse using this calibration curve. Syllabus link See Topic 2 the sample is vaporised, ionised, accelerated (electric field), deflected (magnetic field) and detected. The ions with the largest mass (m/e ratio) are deflected least and the smallest m/e ratio are deflected most. Figure 2_3: Calibration curve of a sample of tap water 17