Most classroom thermometers are now alcohol thermometers so you will not need worry about mercury spills. Length Length is part of linear, area and volume measurement so care is needed here. Using the very end of a scale can sometimes cause errors since the end may be worn away through use. Many scales, even cheap plastic ones, solve this problem by starting the scale well inside the physical end. If the end of the scale is placed physically at one of the fiduciary marks, 1-2 mm error will enter in the measurement.
Many scales have an appreciable thickness.
For example, most meter sticks are 3-5 mm thick with the number scale on top of the ruler. If the stick is layed along side the length to be measured, the reading will depend on the relative position of your head. The solution is to place the meter stick on its edge so that the numbered scale is in contact with the dimension to be measured. When in contact there is no parallax. Volume A graduated cylinder or graduated beaker provides a convenient tool to measure liquid volumes.