It is often necessary to measure large volumes (100 mL – 2 L) of solution rather accurately. The ultimate equipment for this job are flat bottomed volumetric flasks, the spherical globes with the long vertical neck. Such precision is usually not required in secondary school, especially because titration solutions should be standardized prior to use. Relatively accurate measurements may be made using devices that are found in every village: plastic water bottles.
The trick is that because water bottles are made in a factory by injection molding, they are essentially all identical in size. Most bottles have various markings molded into the bottle, and since the engineers that design these bottles tend to prefer round numbers, many bottles have very convenient marks.
Borrow a graduated cylinder and find samples of various water bottles. Iden- tify the volume of every useful mark on the bottles and then share the informa- tion widely.
Volumes not immediately measurable with bottles may sometimes be mea- sured by addition or subtraction of bottle measures. Remember those egg timer problems?