LEGO Chemistry!

Chemistry is an abstract thing.  I do not possess the ability to show students how bonds are broken and reformed in real time.  We have to use models.  A particularly peevish concept to teach is that of conservation of mass.  I've jumped into balancing chemical equations with students and lost most of them immediately.

So...nowadays I bust out the LEGOs.

Before we multiply coefficients and compare reactants with products, we get a sense for how mass is held constant through a chemical reaction.  Students make something out of LEGOs.  They record the mass.  Students combine their construct with another and record the total mass.  Students break their object into several smaller objects and record the mass.

Besides the small differences in measurements (we discuss the to err is to be human idea), the total mass of the objects remains constant.

Now, we can talk about how elements combine to form products knowing that nothing will be created or destroyed.  Just substitute chemical symbols in for bricks.