Ask your science technician to set out your practical equipment with pre-measured/weighed ‘doses’ of reagents. These can be laid out in separate containers which your equipment managers can collect and bring back to their group. This has a number of benefits:
- Speeds up the practical – particularly where you have limited numbers of balances or measuring cylinders;
- Prevents queuing, and the poor behaviour that goes with it;
- Reduces the risk of spillages – this is particularly important with nastier chemicals
- Massively reduces waste and cross-contamination – pupils often pour excess reagent down the drain;
- Equipment is more easily tidied away.
It is important that your lab technician is given precise instructions, and given plenty of notice. This preparation takes time, but will benefit your lesson.
Measuring out chemical volumes/quantities is an important skill in science. Make sure that you give your students opportunities to learn accurate, safe and skilful measuring technique. But this can be a lesson (objective) all in itself, where you are not so worried about the results of an investigation