Half of Year 4 still say sand is a liquid, because it pours. Two children each tip a jug, one of dry play sand and one of water, from the same height into two clear trays set side by side in front of a sheet of black card, while a school tablet on a stand films close up in slow-motion mode, framed on the jugs, the trays and the children's hands. At full speed the two pours look alike, and the class writes down what it saw: both ran out of the jug and both filled the tray. Then the teacher plays the footage on the board. Slowed down, the sand comes out as separate grains that knock into each other, bounce off the tray, stop where they land and build a heap with sloping sides. The water leaves the jug as one stream, breaks into drops, and the drops join again in the tray, spread to every corner and settle with a flat top. The teacher replays the landing twice and freezes it on one bouncing grain and one drop. Children draw both pours in mid-air and after landing, and write which rule for a solid each grain of sand keeps and the water does not.
Tools: Built-in camera (slow motion and time-lapse) Nine ideas for your own version in Generate
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