Safety Precautions in Integrated Science Experiments

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SAFETY PRECAUTIONS IN INTEGRATED SCIENCE EXPERIMENTS PHYSICAL SCIENCES SECTION ADVISORY INSPECTORATE EDUCATION DEPARTMENT 1999 PREFACE This pamphlet is a revised edition of the one published in 1995. There are some changes and additions. Aiming at promoting laboratory safety in the teaching of Integrated Science, the pamphlet highlights the safety precautions to be taken in experiments and activities as suggested by the CDC Syllabus for Science (Secondary 1-3). For easy reference, the experiments and activities listed in part III of the pamphlet are in the order as they appear in the CDC Syllabus. Teachers are also advised to make reference to the pamphlet Safety in Science Laboratories published by the Education Department for more information on laboratory safety. It must, however, be emphasized that the advice and information offered in this pamphlet are inevitably not exhaustive and do not preclude the need for exercising care and good judgement at all times in safe- guarding against laboratory accidents. Comments and suggestions are welcome and should be directed to the Principal Inspector, Physical Sciences Section, Advisory Inspectorate, Education Department, Room 1208, Wu Chung House, 213 Queen’s Road East, Wan Chai, Hong Kong or the e-mail address Physical Sciences Section Advisory Inspectorate Education Department 1999 CONTENTS Page I. PROPER USE OF PROTECTIVE EQUIPMENT 1 II. SAFE USE OF GAS TAPS 2 III. SAFETY PRECAUTIONS IN EXPERIMENTS / ACTIVITIES Unit 1 Introducing Science 3 Unit 2 Looking at Living Things 7 Unit 3 Energy 8 Unit 4 Matter as Particles 10 Unit 5 Solvents and Solutions 15 Unit 6 Cells and Reproduction 17 Unit 7 Living Things and Air 18 Unit 8 Making Use of Electricity 20 Unit 9 Making Heat Flow 21 Unit 10 Hydrogen, Acids and Alkalis 23 Unit 11 Detecting the Environment 26 Unit 12 Forces and Movement 29 Unit 13 Food and Transport 31 Unit 14 Materials from the Earth 35 Unit 15 Electricity and Electronics 39 IV. EXPERIMENTS/ACTIVITIES NOT RECOMMENDED 42 APPENDICES A Hazard warning labels 44 B Hazards in the use of naphthalene in science experiments 45 C Wormery for earthworm/snail house 46 D Experiments involving animal blood, cell and human saliva 47 E Some common plants known to be poisonous 49 F Handling and killing of rats for dissection 50 i Page G Sterilization of boiled seeds for experiments on respiration 51 H Safety precautions in handling micro-organisms 52 I Safety precautions in using extra high tension (E.H.T.) power supply 54 ii I. PROPER USE OF PROTECTIVE EQUIPMENT (i) Safety spectacles/ Face shield/ Safety screen Teachers, pupils and laboratory staff, when working in the laboratory, should wear safety spectacles in all circumstances wherever there is any potential risk of eye injury. Safety spectacles should always be put on when heating chemicals, handling acids, alkalis and other corrosive chemicals, working with glass apparatus under pressure, or carrying out potentially violent or exothermic reactions. Scratched or defective safety spectacles should be replaced without delay because they may affect visibility and cause strain to the eyes or fail to serve their protective function. Dirty safety spectacles should be cleaned with a detergent or disinfectant (e.g. diluted Savlon) as appropriate. If a teacher intends to demonstrate potentially dangerous experi- ments in front of a class of pupils, the safety screen should be used to isolate the apparatus from the pupils. The teacher should also put on proper protective equipment, such as a pair of safety spectacles or a face shield, for his/her own protection. (ii) Protective gloves Teachers and laboratory staff, when handling animals and killing animals for dissection e.g. rats, should wear leather gloves so as to avoid being bitten or scratched. Students should also put on surgical gloves during dissection. When working with wormery/snail house or handling microbiological experiments, disposable gloves should be worn in order to prevent infection. Furthermore, chemical resistant gloves should be put on when handling acids, alkalis and organic solvents if necessary, whereas heat/cold resistant gloves should also be used when dealing with furnace or hot plate in the laboratory for protection. 1 II. SAFE USE OF GAS TAPS Schools should take safety precautions to prevent accidents due to inappropriate use of gas taps. The main gas supply valve of the laboratory should only be turned on when gas supply is required, and all downstream gas taps inside the laboratory must be in the OFF position before the main valve is turned on. Teachers and laboratory technicians must ensure that Bunsen burners are properly connected to the gas taps before experiments. Schools should also properly secure all unused gas taps in order to prevent them from being mistakenly turned on by pupils. The ways to secure the common types of gas taps are given below for teachers’ and laboratory technicians’ reference. (1) Pressdown type gas tap The unused gas tap can be hose clip secured by fixing a hose clip under the gas tap knob to prevent it from being turned on mistakenly. (2) Gas tap with automatic shut-off facility and a safety valve The unused gas tap can be cable tie tied up, such as by using a nylon cable tie, to prevent it from being turned on mistakenly. 2 III. SAFETY PRECAUTIONS IN EXPERIMENTS/ACTIVITIES Unit 1 Introducing Science Experiments/Activities Safety Precautions C.1 Mixing solutions Mix solutions of Label the containers of chemicals with chemicals and make hazard warning labels. Provide pupils observations. with short blunt-end droppers. Pupils should wash their hands after performing experiments in which chemicals have been used. Explain to pupils the meanings of the hazard warning labels. (See Appendix A for details.) Teach pupils the proper way to hold a reagent bottle and to get solution from it. Remind pupils not to return excessive chemicals back to reagent bottles. C.2 Measuring temperature, weighing and volume Blindfold a pupil. Place Do not use hot water above 50oC. one of his hands in hot water and the other in ice water. 3 Experiments/Activities Safety Precautions Measure the temperature As it is probably pupils’ first time to of air, tap water, icy wa- use a thermometer, to play safe, pro- ter , hot water and molten vide them with the alcohol type to wax, etc. start with. Help pupils to develop the good habit of returning the thermom- eter back to its casing immediately after experiment and putting it in a safe place. Teach pupils the correct way of using a Bunsen burner, including that the hand should be lower than the top of the chimney when lighting a burner. If a sharper melting temperature is desired, octadecan-1-ol may be used to replace wax. Do not use naphthalene to replace wax as the former produces harmful vapour. (See Appendix B for details.) C.3 Dissolving, evaporation, filtration Evaporate salt solution to Pupils should wear safety spectacles dryness. in this experiment. Heat gently towards the end of evapo- ration to avoid splashing out of the hot salt solution. If salt begins to ‘spit’ from the solution, turn off the Bunsen flame. Heating over a beaker of boiling water can be a better alternative to direct heating. 4 Experiments/Activities Safety Precautions Never invite pupils to taste the salt formed. C.4 Using a stop-watch to measure small time intervals Count the pulse rate/ If the effect of physical exercise on heartbeat for one minute. pulse rate/heartbeat is to be measured, teacher should note that pupils who are exempted from Physical Educa- tion lessons for medical reasons should not be allowed to perform this experiment. C.5 Making observations and recording results Pull two rubber suckers The experiment should be conducted apart. in a more spacious part of the laboratory. Ensure no glassware is nearby. Remind pupils not to apply a sudden force to pull the rubber suckers apart. Blow air into a stoppered Ask pupils to handle glass tubings bottle containing water carefully. Use clean rubber tubings for and make observations. blowing. Warn pupils not to over- exert themselves in blowing. Teacher should note that pupils who are exempted from Physical Education lessons for medical reasons should not be allowed to perform this experiment. 5 C.6 Looking at differences within one kind of organism Measure the volume of Use clean rubber tubings for blowing. one’s lungs by blowing air As this experiment may exert exces- to displace water in a sive physical stress on some pupils, plastic bottle. teachers should note that pupils who are exempted from Physical Educa- tion lessons for medical reasons should not be allowed to perform this experiment. Do not replace the plastic bottle by a glass one as the latter is quite heavy and may be broken easily. 6 Unit 2 Looking at Living Things Experiments/Activities Safety Precautions C.1 Looking at snail/earthworm Activities involving the Wear disposable gloves to prevent handling of earthworms the transmission of germs/parasites or snails. from the animals to pupils. After the experiments, all bench tops should be washed with disinfectant solution and all pupils involved should have their hands thoroughly washed. Keep wormery or snail house in hygienic conditions. (See Appendix C for details.) 7 Unit 3 Energy Experiments/Activities Safety Precautions C.2 Simple energy changes Burn a magnesium ribbon Pupils should wear safety spectacles and observe. in this experiment.Warn pupils not to look directly at the bright flame which may cause harm to the eyes. Hang a weight with an Use a light weight for the experiment, elastic band and then say 20 g. allow it to oscillate. Heat the lower opening of Ensure that the long tube is firmly a tube with wire gauze in clamped and the stand is stable it to produce sound. enough by putting enough weights on the base of the stand. Take care that the tube may become very hot. C.3 More examples of energy changes Demonstrate charging Ensure that the two lead plates will and discharging of lead- not touch each other, otherwise short- acid cell. circuiting results causing damage to the low voltage power supply unit. C. 5 Energy converters and daily applications Use a steam engine and a Before experiment, ensure proper dynamo to convert energy functioning of the valve of the boiler. stored in fuel to electrical Excessive building up of pressure in energy. the boiler may lead to an explosion. 8 Experiments/Activities Safety Precautions Some solid fuels accompanying the steam engine may be harmful. Read instructions and take necessary precautions. If alcohol is used as the fuel, do not add alcohol to the fuel-containing vessel while the vessel is still hot. C.6 Energy in food Burn food samples over a Pupils should wear safety spectacles Bunsen burner. in this experiment. Do not burn fats, as hot oil droplets may jet out and cause burns. Clean the Bunsen burners after the experiment as spillage of food tends to block the chimney of the burners. 9 Unit 4 Matter as Particles Experiments/Activities Safety Precautions C.1 State of matter Arrange materials If nitrogen(IV) oxide is selected as provided into solids, an example of gas, remind pupils of liquids and gases. the toxicity of the gas. Cover the container properly and place it inside a fume cupboard. Do not use bromine as it is more hazardous than nitrogen(IV) oxide. Heat some substances Pupils should wear safety spectacles (e.g. ammonium carbon- in this experiment. ate or copper(II) nitrate) Use only a small amount of the in a test tube and note the substances. gas produced. Ask pupils not to inhale the gas directly. Show pupils the correct way of detecting the odour of a gas by using a hand to fan the gas towards the nose. Iodine vapour is harmful. If experi- ment on heating iodine is to be done, it should be performed as a teacher’s demonstration in a well-ventilated laboratory or in a fume cupboard. C.2 Particle size Make a solution with a Remind pupils not to touch the single potassium potassium manganate(VII) crystals manganate(VII) crystal. with their bare hands. The crystal will turn the skin brown due to oxidation. 10 Experiments/Activities Safety Precautions C.3 More about particles Demonstrate diffusion Take care not to allow the toxic gas using nitrogen(IV) oxide. to escape out of the gas jars. Ensure good ventilation or perform the experiment inside a fume cupboard. Do not replace nitrogen(IV) oxide by bromine as bromine is more hazardous. S.4 Particles - more to do Perform dilution experi- Pupils must not normally be allowed ment and taste orange to eat or drink in the laboratory. When juice at different dilutions. these activities are essential to their studies, clean domestic containers and drinking water should be used. C.5 A particle model Demonstrate with a kinetic Polystyrene beads fallen on the floor motion model. can be dangerous as they are very slippery. Avoid dropping the beads onto the floor. C.6 Gas pressure Compress gas inside a Do not provide needles for the syringe. syringes. 11 Experiments/Activities Safety Precautions Demonstration: Remove Never allow pupils to stand too close air directly with a vacuum to the vacuum pump while it is turned pump from a metal can on. until it collapses. Demonstration: Remove Check the apparatus before the air from the Magdeburg experiment to ensure that it will not hemispheres using a break apart very easily upon pulling. vacuum pump. Then try to To avoid accidents, remind pupils that separate them. the apparatus will suddenly break apart upon pulling. The experiment should be conducted in a more spacious part of the laboratory. Ensure no glassware is nearby. Measure lung pressure by Ask pupils not to over-exert them- blowing strongly into a selves in blowing. Bourdon gauge. Teacher should note that pupils who are exempted from Physical Educa- tion lessons for medical reasons should not be allowed to perform this experiment. C.7 Density Demonstration: Add sol- Take care not to spill mercury or ids to a jar containing lay- expose pupils to mercury vapour, ers of immiscible liquids which is hazardous to health. (e.g. oil, water and The jar should not be made of glass mercury). which is easily be broken when heavy solids are dropped into the jar . In case of spillage or leakage, collect 12 Experiments/Activities Safety Precautions large drops of mercury immediately with a dropper. Cover remnants of mercury with zinc dust (or a paste of sulphur and lime), and leave for a few hours, then collect them as chemical wastes. Demonstration: Raise a Beware of the potential fire hazard of plastic bag by hot air from the experiment. Have fire fighting burning alcohol. equipment ready. Hold the cotton pad soaked in alco- hol in a metal dish but not in a watch glass. Never use a Bunsen burner in place of burning alcohol to lift up the plastic bag. C.8 Heating substances Heat the bar or the bi- Remind pupils to handle the hot metallic strip in thermal apparatus with care. expansion experiment. E.8 More applications of thermal expansion Examine an aquarium The heater should be operated in heater with a thermostat water to avoid danger resulting from and see how it works. over-heating of the heating wire. Demonstrate working of Remind pupils to handle the hot fire alarm using bimetallic bimetallic strip with care. strip. 13 Experiments/Activities Safety Precautions C.9 Joining and separating particles Demonstration: Heat Make use of safety spectacles/safety metal (e.g. copper screen. turnings, iron filings) with Toxic sulphur dioxide gas will be sulphur in test tubes. produced. Use small amount of the chemicals. Ensure good ventilation in the laboratory or perform the dem- onstration in a fume cupboard. Reaction between sulphur and iron filings may be vigorous. Stop heating once glowing starts to spread through the tube. Demonstration: Drop a Carry out the experiment in a fume piece of Dutch metal into cupboard as fumes and heat are a jar of chlorine. evolved, and chlorine is poisonous. Electrolyze copper(II) Use minimum amount of copper(II) chloride solution. chloride to avoid large quantity of poisonous chlorine gas being evolved. Ensure adequate ventilation. 14 Unit 5 Solvents and Solutions Experiments/Activities Safety Precautions C.1 Finding out about water Effect of adding salt on the Pupils should wear safety spectacles boiling point of water. in this experiment. Never stir water with the thermometer. Alert pupils not to let the bulb of thermometer touch the bottom of the flask/beaker. C.3 Water purification Filter muddy pond water Pupils should wear safety spectacles and evaporate the filtrate in this experiment. to dryness. Heat gently towards the end of evapo- ration to avoid splashing out of the hot liquid. Heating over a beaker of boiling water can be a better alterna- tive to direct heating. Distil the filtrate and In distilling the filtrate, add anti- evaporate the distillate to bumping stones (pumice stones or dryness. broken porcelain) to the filtrate to avoid uneven heating which may result in shooting out of hot liquid. C. 4 Dissolving Dissolve substances (e.g. Pupils should wear safety spectacles sodium hydroxide) into in this experiment. water and measure the Warn pupils of the corrosive nature temperature change. of sodium hydroxide and ask them to handle it with care. 15 Experiments/Activities Safety Precautions C.6 Solvents other than water Test the solubility of Warn pupils of the harmful nature of iodine in different liquids. iodine. Use minimal amount of the chemical and handle it with care. Test the solubility of Toluene is flammable and harmful. sulphur in water and Use minimal amount of the solvent methylbenzene(toluene). and ensure good ventilation. Find a suitable solvent for Propanone, ethyl ethanoate and nail varnish and lacquer. ‘thinner’ are flammable. Use minimal amount of the solvents and ensure good ventilation. 16 Unit 6 Cells and Reproduction Experiments/Activities Safety Precautions C.2 Animal and plant cells Observe animal cells Do not use human cheek cells as there under a microscope. is a potential danger of transmitting blood-borne diseases. Use other sources of animal cells or commercially prepared slides. (See Appendix D for details.) C.4 Reproduction in plants Examine different parts of Some pupils may be allergic to pollen a flower and pollen grain. grains, remind them not to handle flowers or pollen grains. Avoid using plants known to be poisonous.(See Appendix E for details.) C.6 Mammal development Look at dissection or If dissection is intended, ensure that prepared specimens of a the animal is healthy and clean. pregnant rat/rabbit. Dissection should be done by teacher or laboratory technician.(See Appendix F for details.) If specimen preserved in formalin (methanal solution) is to be used, ensure that the specimen jar is well covered, as methanal vapour irritates the respiratory system, skin and eyes. 17 Unit 7 Living Things and Air Experiments/Activities Safety Precautions C.3 Breathed and unbreathed air Collect breathed air and Excessive rebreathing of the same compare its composition sample of air is dangerous. with that of unbreathed air. Pupils exempted from Physical Edu- cation lessons should not be allowed to breathe in and out of the plastic bag. C.4 Breathing system in man Examine a pig’s lung. Use clean and fresh lungs. Specimens provided by abattoirs may carry germs. Pupils should cover any wounds on their hands with water- proof dressings and wear surgical gloves to prevent infection when handling the specimen. After the experiment, all bench tops and instruments used should be washed with disinfectant solution, whereas pupils involved should have their hands thoroughly washed. C.6 Formation of starch in green plants Test for the presence of Alcohol is flammable. When alcohol starch in leaves. is used, ensure that there is no flame nearby. Small and thin leaves should b
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