Besides actual and active touching of materials and appa-
ratus (physicality per se) the enactment of PME also requires
manipulation of these materials and apparatus. Manipulation is
a process that requires from a learner to intentionally interact
with material and apparatus in a skilful manner (in the case of
PME it involves certain motor skills, different from those
involved in VME). In other words, learners move, arrange,
operate, or control by hand the materials and apparatus.
Manipulation is usually defined and guided by the design and
context of an experiment (e.g., through accompanying
teaching material or instructions). No PME could be
conducted, unless there is both a purposeful exploration
through active touching (physicality) and intentional manip-
ulation of materials and apparatus. For instance, if one of the
tasks of an experiment is to bring a sample of water in a beaker
at a certain temperature (higher than the one it had before)
through the use of a hotplate, it is not enough to just touch the
beaker, the hotplate or the thermometer. For such a task,
someone needs to position the beaker on the hotplate, insert
a thermometer within the water and turn on the hotplate for
a certain period of time until it reaches the expected
temperature.