A few reflections on lab 8 from S&P:
Students did not understand what type of observations to record in the data table. If I were to re-make this data table, I would include a column for each specific observation I wanted the students to make.
Many students said the precipitate came from nowhere, rather than saying that it was formed by the chemical reaction between the iron chloride and the sodium carbonate.
It was common for the iron chloride solution to have some specks of iron in it, even after stirring. The precipitate formation is still obvious, but perhaps the results would be more dramatic if there were no solids in the small cups to begin with. One way to solve this problem and simplify this lab would be to make up an iron chloride solution before hand, and give it to students in bottles. Or, you could have students filter the iron chloride solution, which would further illustrate the difference made by the precipitation reaction (i.e. it lets you filter out something that previously went through the filter).