Grow crystals from table sugar (sucrose). Look at their shape and/or eat them.
Science content (2016 curriculum):
Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)
Chemistry: Crystals (7)
Science topic (2005 curriculum connection):
Physical Science: Properties of Objects and Materials (grade K)
Physical Science: Chemistry (grade 7)