Comparing Capacity

Today's goal-- work on comparing volumes and in the process practice counting and writing numbers.  I filled a giant plastic bin with as many different sizes and shapes of empty containers as I could gather.  I labeled each container A through Z.  (Multiples of a particular size/shape were labeled with the same letter.)  Then I challenged the class to determine which of a pair of containers was larger.  We discussed various possibilities for determining a container's volume and settled on filling the containers with various math manipulatives and comparing total capacity.  Then students set to work.  Was this lesson actually differentiated?  I'm not certain, but if I were to try to make the case that it is, I'd label it an open-ended problem-solving activity.  Because students chose for themselves which containers to compare and chose for themselves which math manipulatives to measure with, each child adjusted the level of counting and comparing difficulty for themselves.