Teachers' guide 2 - National STEM Centre

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302 Appendix 4 When opening ampoules or bottles with seized stoppers great care is required. Seized stoppers should be gently tapped on both sides with a piece of wood to release them. Failing this a cut is made in the neck of the bottle with a file and a hot wire or glass rod applied to the cut. The latter procedure should be adopted when opening ampoules, and should always be done in a fume cupboard b Pipettes - Safety pipettes of the aspirator type should always be employed when measuring liquids. c Desiccators (vacuum) - These are capable of implosion when used under vacuum and, therefore, a safety screen should always be used to protect the operator. d Bunsen burners - These should only be left on when in use. If they have to be left on for some time the air hole should be closed to give the smoky yellow visible flame. e Electrical apparatus - Electrical equipment should always be earthed properly and three-core 10 ampere cable used for connections between apparatus and supply. It should never be used with wet hands or when standing on wet surfaces. If liquids are spilled on electrical apparatus it should be thorDughly dried and tested before use. Makeshift connections and slipshod assembly are common causes of accidents and must be avoided. 2 Handling and storage of chemicals Toxic and explosive compounds will be dealt with in more detail later. a Spillages - Spillages on the bench or floor should be mopped up immediately, after preliminary treatment if necessary (such as soda ash and washing with water for acids, or sand for oily residues). If inflammable solvents are spilled all naked lights should be immediately extinguished. When possible they should be extinguished before using inflammable materials. b Carrying of chemicals - This should be done in a receptacle which will resist breakage or spillage when large bottles or Winchesters are involved or when chemicals are being carried long distances. Otherwise ensure that the student carries bottles with one hand under the bottom and the other round the neck of the bottle.
Safety c Storage of chemicals i Only the minimum amount of chemicals required for immediate use should be kept in the laboratory. The remainder should be kept in a bulk store. ii Chemicals should be stored according to type and not alphabetically, so that chemicals capable of reacting with one another, for example nitric acid and alcohol, or sodium-dried ether and alcohol, are not stored close to one another. iii Bottles should be carefully and clearly labelled and regularly cleaned. The labels on bottles of hazardous chemicals from reliable suppliers bear warnings of the hazards and these should be transferred along with the name to secondary containers. iv Chemicals in the laboratory should be made as accessible as possible allowing for safe working. They should not be placed on shelves above eye level and should not be stocked along the centre of the bench unless they are placed on shelves having short projections along the front to prevent bottles falling off accidentally. Wall mounted shelves situated near to the bench, to cut down unnecessary transportation, are more useful. Strong acids and bases should be stored on an inert base such as glass. v Bulk chemicals should be kept in an outside store and, if possible, inflammable solvents should be kept in an outhouse away from the main building. vi Chemicals which are subject to decomposition should not be stored in bulk (for example ether, which forms explosive peroxides). Others with high vapour pressures (for example ammonia) should be stored in a cool place away from direct sunlight. vii Toxic substances, in particular scheduled poisons, should be locked in a cupboard, the key of which is readily accessible to staff but not to students. 3 Protective clothing The necessity of protective clothing and headgear is not always felt by teachers. Many consider that students are not exposed to risks which are serious enough to warrant the cost of safety clothing. In the short term this assumption may be justified but from the long term point of view this is not so. Students should be encouraged to purchase and wear laboratory coats and a suitable supply of safety goggles and gloves should always be available for use when required. For example, if a student is pouring out concentrated sulphuric acid, he should always use goggles and gloves. Many teachers do not allow students to do this but do it themselves or delegate the laboratory technician to do it. In either case the same precautions should be taken. It is imperative that the right kind of example is set by instructors. It is at this stage more than any other that correct laboratory discipline is needed. If a teacher always wears a laboratory coat at this stage students will follow. 303
Page 1 and 2: Appendix 1 Nomenclature, units, and
Page 3: Nomenclature, units, and abbreviati
Page 6 and 7: 262 Appendix 2 Rubber caps for 100
Page 8 and 9: 264 Appendix 2 Adjustment will be r
Page 10 and 11: 266 Appendix 2 Construction The ins
Page 12 and 13: 268 Appendix 2 FigurcA.7 Box and li
Page 14 and 15: 270 Appendix 2 The box is then furt
Page 16 and 17: 272 Appendix 2 polaroid cork protra
Page 18 and 19: 274 Appendix 2 light, so the instru
Page 20 and 21: 276 Appendix 2 Before these curves
Page 22 and 23: 278 Appendix 2 These can be conveni
Page 24 and 25: 280 Appendix 2 The components requi
Page 26 and 27: 282 Appendix 2 screw clip Figure A.
Page 28 and 29: 284 Appendix 2 solutions required f
Page 30 and 31: 286 Appendix 2
Page 32 and 33: 288 Appendix 3 For this course a nu
Page 34 and 35: 290 Appendix 3 By the use of rubber
Page 36 and 37: 292 Appendix 3 For further informat
Page 38 and 39: 294 Appendix 3 Transparencies have
Page 40 and 41: 296 Appendix J Other film loops are
Page 42 and 43: 298 Appendix 3 display board (figur
Page 45: Appendhc4 Safety A correct attitude
Page 49 and 50: Safety Cuts - Staunch the bleeding
Page 51 and 52: Name benzoyl chloride bromine bromo
Page 53 and 54: Name 2-naphthol nitric acid nitro b
Page 55 and 56: Appendix 5 Examinations and tests T
Page 57 and 58: Examinations and tests In many resp
Page 59 and 60: Examinations and tests available to
Page 61 and 62: Examinations and tests The form of
Page 63 and 64: Examinations and tests in order to
Page 65 and 66: Examinations and tests Information
Page 67 and 68: Examinations and tests Example A Re
Page 69: Examinations and tests Example B An
Page 72 and 73: 328 Appendix 6 most effective way o
Page 74 and 75: 330 Appendix 6 Programme writers ar
Page 76 and 77: 332 Appendix 6 5 Remedial programme
Page 78 and 79: 334 Appendix 6 non-experimental pro
Page 80 and 81: 336 Appendix 6 It is generally agre
Page 82 and 83: 338 Reference sources and bibliogra
Page 84 and 85: 340 References sources and bibliogr
Page 86 and 87: 342 Reference sources and bibliogra
Page 89 and 90: Index References to specific salts
Page 91 and 92: Index endothermic reactions, equili
Page 93 and 94: Index paper chromatography, 218, 21
Page 95 and 96: Acknowledgements The Nuffield Found
Page 97 and 98:
Acknowledgements Chemistry teachers
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Teachers' guide 2 - National STEM Centre

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