Good laboratory work depends on choosing the correct apparatus, handling materials safely, and knowing what to do in an emergency. Careless handling can cause injuries or spoil results.
Choosing the right apparatus
Different apparatus have different jobs. Choosing the wrong one gives inaccurate data.
| Apparatus | Use |
|---|---|
| Measuring cylinder | Measure an approximate volume of liquid |
| Pipette | Measure an accurate fixed volume |
| Burette | Deliver a variable, accurate volume (titration) |
| Electronic balance | Measure mass accurately |
Hazard symbols
Chemical containers carry hazard warning symbols, for example: flammable, corrosive, toxic, oxidising and irritant. Always read the label before use.
Key idea / 要点
The choice of apparatus depends on the accuracy needed. For an exact fixed volume use a pipette; for a rough volume a measuring cylinder is enough.
Worked example / 例题
A student must add exactly 25.0 cm³ of acid for a titration. A measuring cylinder is only accurate to about ±1 cm³, so it is unsuitable. The correct choice is a pipette (for the fixed 25.0 cm³) delivered into the flask, with the acid run from a burette if the volume must vary.
Safe handling and management
- Wear safety goggles and a lab coat.
- Never taste chemicals; smell gases by wafting only.
- Heat liquids gently, pointing the tube away from people.
- Label bottles and store flammable liquids away from flames.
- Dispose of waste in the correct container, not the sink, when told.
Good management of materials also means using only the amount needed, returning unused chemicals to the correct bottle only when instructed, and keeping the work area clean and dry. Reactive metals such as sodium are stored under oil, while acids and alkalis are kept apart. Careful storage and clear labelling prevent dangerous mix-ups and make the laboratory safer for everyone.
Remember / 记住
- Match the apparatus to the accuracy required.
- Read hazard symbols before handling any chemical.
- Report spills and accidents to the teacher at once.