PRE-PUBLICA TION EDITION - Nelson Education

2Scientific Tools and EquipmentSelecting the correct tools and equipment and usingthem properly are essential for your safety and thesafety of your classmates.2.A. Working with DissectingEquipmentDissection tools are very sharp and must be handledcarefully. Read through the following safety tipsbefore you begin any dissections (Figure 1).• Always hold the dissection tool by the handle.• To move dissection equipment to and from yourworkstation, place all tools in the dissection trayand carry the tray with both hands. Do not carrytools by hand. If you forgot a piece of equipment,carry the tray back to get what you need.• At your workstation, imagine your dissectiontray sitting in the middle of a 30 cm circle (aboutthe size of a large dinner plate). The tools neverleave this circle. If you leave your workstationor turn to answer a question, place the tools inthe dissection tray. Tools must always lie flat onthe inside or outside of the dissecting tray, notpropped up on the side of the tray.• Always cut away from yourself and others. Cutdownward onto a tray.• If you are asked to rinse a tool after you haveused it, remember that the tool is sharp. Hold itby the handle and rinse it under running water;do not wipe sharp edges or points.2.B. Testing for ElectricalConductivityBefore you start any conductivity testing, ask yourteacher for specific operating instructions on yourschool’s equipment (Figure 2). Devices used to testelectrical conductivity vary considerably. Two metalelectrodes are inserted into the sample to be tested.Figure 2 You should use only low-voltage (battery-powered)conductivity testers.In many cases, if the sample conducts electricity,the conductivity tester gives a positive result (e.g., alight bulb turns on). Some conductivity testers givevariable results (Table 1).Table 1 Results of Conductivity TestingObservationbright glowfaint glowno glowSamplegood conductorpoor conductornonconductor (insulator)2.C. Using the pH MeterpH meters are used to measure acidity or alkalinity(Figure 3). Your teacher will provide specific operatinginstructions for your school’s pH meters. Most pHmeters need to be calibrated by placing the probeinto a solution of a specific pH and then adjusting themeter so that it displays this pH value.Figure 1 Use safety equipment and always work within a30 cm circle at your workstation when dissecting.Figure 3 A pH meter604 Skills Handbook NEL