For Day 69, students observed a variety of chemical reactions including smashing thermite, the blue bottle, mossy zinc and hydrochloric acid and of course igniting hydrogen balloons from the hydrogen gas produced from the aforementioned reaction. I always get a few chuckles when I introduce my old-fashioned laser pointer.
Students observe the reactions and note any “giveaways” that a chemical reaction has occurred. Once we have a list of macroscopic observations that help us identify a chemical reaction, we can talk about what is going on at the particle level.
I use the Zn and HCl reaction to write our first chemical equation. Students predict the formation of zinc chloride and then draw particle models of the reaction. Without balancing, the equation does not follow the law of conservation of mass. Students then use particle models to balance the equation. I have also used ball and stick models (which I do not care for) and bingo chips to demonstrate that during a chemical reaction, particles are rearranging.