Make bread, experiment to find out what ingredients make gas to make the bread rise, and model the chemical reaction that makes the gas.
Science content (2016 curriculum):
Biology: Features, Adaptations of Living Things (K, 1, 3, 7)
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Atoms, Molecules (3-7)
Chemistry: Chemical Changes (2, 7)
Curriculum connection (2005 science topic):
Physical Science: Chemistry (grade 7)